Colonial waterbird breeding in Australia: wetlands, water requirements and environmental flows

Transcription

1 Colonial waterbird breeding in Australia: wetlands, water requirements and environmental flows Kate Brandis PhD Thesis Australian Wetlands and Rivers Centre School of Biological, Earth and Environmental Sciences University of New South Wales 29th September 2010

2 Originality statement I hereby declare that this submission is my own work and to the best of my knowledge it contains no materials previously published or written by another person, or substantial proportions of material which have been accepted for the award of any other degree or diploma at UNSW or any other educational institution, except where due acknowledgement is made in the thesis. Any contribution made to the research by others, which whom I have worked at UNSW or elsewhere, is explicitly acknowledged in the thesis. I also declare that the intellectual content of this thesis is the product of my own work, except to the extent that assistance from others in the project s design and conception or in style, presentation and linguistic expression is acknowledged. Kate Brandis 29 th September

3 Preface This thesis consists of four research papers (Chapters 2-5) an introductory chapter (Chapter 1) and a concluding chapter (Chapter 6). Chapters 2-5 have been written for submission or been submitted to peer reviewed journals, each chapter is an individual paper and consequently some repetition occurs. In addition, tables and figures are not numbered sequentially throughout the thesis but are specific to the chapter/paper in which they appear. References are located at the end of the paper in which they are referred to. This thesis is a compilation of my own work with guidance from my supervisor Richard Kingsford and contributions from co-authors as outlined below. I conceptualised my research, conducted all data analysis and wrote and illustrated the manuscripts. My co-authors proof-read and edited the final manuscript versions. The contributions of my co-authors are detailed below. Chapter 2: Brandis, K., Ramp, D., and Kingsford, R.T. Colonial waterbirds: wetland use and vulnerability at a continental-scale. D. Ramp contributed significant intellectual input and assisted with habitat model development and model scripts in R Language. R.T. Kingsford provided conceptual guidance and advice in his function as my supervisor. Chapter 3: Brandis, K., Kingsford, R.T., Ren, S., and Ramp, D. Impacts of water resource development on colonial waterbird breeding. In review Ecological Applications. R.T. Kingsford provided conceptual guidance and advice in his function as my supervisor. S. Ren assisted with development of flow models while D. Ramp assisted with CART analysis and generalised linear models. Chapter 4: Brandis, K. and R.T. Kingsford. Crisis water management and ibis breeding at Narran Lakes in arid Australia. In press Environmental Management. R.T. Kingsford provided guidance regarding survey design and data analysis and advice in his function as my supervisor. 2

4 Chapter 5: Brandis, K. and R.T. Kingsford. Management of environmental flows for colonial waterbird breeding in Australia. R.T. Kingsford provided significant intellectual input, conceptual guidance and advice in his function as my supervisor. Acknowledgements This study was supported by a range of organisations both financially and in-kind. These included the Australian Wetlands and Rivers Centre at the University of NSW, The Murray-Darling Basin Authority, and the NSW Department of Environment and Climate Change, National Parks and Wildlife Service. I would like to acknowledge and thank many people for their help and support throughout the duration of my candidature. Richard Kingsford, my supervisor; Shiquan Ren and Daniel Ramp, co-authors. Field data were collected with the valuable assistance of the Parks and Wildlife Group of NSW Department of Environment, Climate Change and Water on Narran Lakes Nature Reserve. I particularly thank Michael Mulholland, Duncan Vennell, Peter Terrill and Rob Smith (NSW Department of Environment and Climate Change) for field work support and assistance; Mike Maher for his extensive knowledge of Narran Lakes; I also thank Lucy Nairn and John Porter, technical advice and support; the Brandis family, for moral support; and Joon for his endless patience. 3

5 Abstract Colonial waterbirds are particularly dependent on river flows for the critical breeding stage of their lifecycle. They breed in response to large flows on relatively few wetlands in Australia. Most species of colonial waterbirds require sufficient river flows, flooding and availability of suitable nesting habitat. Water resource development through water extraction and impoundment is degrading wetlands around the world, changing the natural flow regime and affecting aquatic organisms, including colonially breeding waterbirds that rely on wetland inundation. To overcome some of the significant impacts of water resource development, there is increasing focus on the management of environmental flows for ecosystems and specific organisms. Colonial waterbirds are increasingly important as a target group of organisms for the management of environmental flows, providing a measure of the success or failure of environmental flow management. My thesis examined the breeding of colonial waterbirds in Australia at a range of scales and the importance of environmental flow management. Chapter 1 set the context by briefly reviewing the impacts of water resource development and its threat to colonial waterbird breeding and then summarising each of the subsequent chapters. Chapter 2 examined the historical use ( ) of wetlands for breeding by colonial waterbirds in Australia and characterised the types of wetlands used for breeding. It also identified important sites in Australia for breeding by colonial waterbirds their characteristics and assessed vulnerability to water resource development. In Chapter 3, I focussed on Narran Lakes, one of Australia s most important colonial waterbird breeding sites and assessed the impact of water resource development on ibis breeding over the period In Chapter 4, I examined the success of the 2008 ibis breeding event at Narran Lakes when, because of declining water levels, a significant volume of water was purchased to ensure that the breeding colony was successful. Finally, in Chapter 5, I reviewed the stimulus and breeding responses of colonially breeding waterbirds in Australia with the aim of identifying the key elements of environmental flows required to successfully manage colonial waterbird breeding. 4

6 Table of Contents Originality statement... 1 Preface... 2 Acknowledgements... 3 Abstract... 4 Chapter 1: Introduction... 6 Chapter 2: Colonial waterbirds: wetland use and vulnerability at a continental-scale Chapter 3: Impacts of water resource development on colonial waterbird breeding Chapter 4: Crisis water management and ibis breeding at Narran Lakes in arid Australia Chapter 5:. Management of environmental flows for colonial waterbird breeding in Australia Chapter 6: Conclusion

7 Chapter 1: Introduction Water resource development threatens wetlands around the world (Dynesius and Nilsson 1994; Mengxiong 1995; Nilsson et al. 2005). Dams, water extraction and diversions impact on the natural flow regimes, reducing flow volumes, variability, and changing patterns of inundation (Ren et al 2009; Thomas et al. in press). This affects flow dependent ecosystems and aquatic organisms (Kingsford and Thomas 1995; Poff and Zimmerman 2010). Many of Australia s river systems, particularly in the Murray- Darling Basin (Kingsford 2000), are impacted by water resource development with diversions of water mainly for irrigated agriculture (NLWRA 2001). This has resulted in a loss or decline in the ecological integrity of many wetland and river systems (CSIRO 2008), including those used by colonial waterbirds for breeding (Kingsford and Thomas 1995; Kingsford and Johnson 1998; Leslie 2001; Driver et al. 2004; Kingsford et al. 2004; Kingsford and Thomas 2004). The breeding of colonial waterbirds is primarily driven by large scale flooding events which occur on highly variable dryland river systems. Australia, as the driest inhabited continent, experiences annual rainfall variability greater than any other continent (BOM 2010), with arid and semi-arid regions accounting for 70% of the land area (James et al. 1999). These produce some of the more variable flow river systems in the world (Bunn et al. 2006; Poff et al. 2006; Young and Kingsford 2006). High rainfall variability results in flow extremes from no flow to large flooding events which stimulate boom-bust ecosystems (Kingsford et al. 1999; Bunn et al. 2006). Consequently when rivers flood, many ecosystems respond rapidly and large numbers of waterbirds arrive and begin to breed (Kingsford et al. in press). As a subset, colonial waterbirds from the orders Pelecaniformes (cormorants and pelicans) and Ciconiiformes (wading birds, egrets, herons, ibis, spoonbills) are an iconic group of organisms that respond to large flows and extensive flooding by breeding in large colonies but usually in relatively few continental locations. 6

8 Outside breeding periods, Australian colonial waterbirds are nomadic rather than migratory (Brooker 1992), with movements often triggered by unpredictable rainfall events, rather than seasonal changes (Carrick 1962; Dodman and Diagana 2007). They use a range of wetland types including inland and coastal wetlands at different times of their life cycle (Marchant and Higgins 1990). Many species opportunistically breed on inland wetlands, taking advantage of suitable habitat after sufficient flooding. The size of the breeding response and its subsequent success is directly related to hydrological conditions (Kingsford and Johnson 1998; Leslie 2001; Taft et al. 2002). Breeding events are often threshold driven, triggered once flow of a certain volume occurs resulting in extensive flooding. Once breeding, the flow regime also dictates the degree of reproductive success by extending the duration of the flood. Wetland flooding produces significant bursts in productivity in food webs with abundant macroinvertebrate emergence, fish recruitment and plant growth, all providing key resources to support waterbird breeding (Jenkins and Boulton 1998; Kingsford et al. 1999; Puckridge et al. 2000, Bunn et al. 2006). In the Murray-Darling Basin, water resource development has changed the natural flow regimes of many river systems affecting colonial waterbird breeding, reducing the frequency of breeding opportunities, and impacting on reproductive success (Kingsford and Johnson 1998; Leslie 2001; Driver et al. 2004). In species that are nomadic and opportunistic and breed on relatively few wetlands, this may have significant implications for continental waterbird populations. To mitigate the impact of water resource development and subsequent flow regulation, environmental flows and their management offer some opportunity to achieve the hydrological conditions required for successful breeding. If there is sufficient water, flow thresholds for breeding can be reached and sufficient flow released to ensure adequate flooding duration. Environmental flows can target ecosystems and ecosystem responses. Due to conservation importance of colonial waterbirds and their responsiveness to river flows and subsequent wetland flooding (Kushlan 1993; Frederick et al. 2009), colonial 7

9 waterbirds represent a group of species suitable for release of environmental flows and measurement of effective management. Colonial waterbirds interact with habitats at a range of scales from the wetland to landscape scale. They travel large distances across the continent to find suitable breeding habitat and select wetlands with specific suites of characteristics required for breeding. This thesis takes a multi-scale approach to studying the interactions of colonial waterbirds with their breeding habitat. It examines the distribution of breeding sites at a continental scale (Chapter 2), the impacts of catchment scale water management on a breeding site (Chapter 3), the reproductive success at a key breeding wetland (Chapter 4) and the management of environmental flows for colonial waterbird management across all sites in Australia (Chapter 5). Chapter 2: Colonial waterbirds: wetland use and vulnerability at a continental-scale In chapter 2, I aimed to assess the vulnerability of colonial waterbirds to threats from water resource development. Using long-term data ( ), I identified wetlands used for breeding by nine species of colonial waterbirds across Australia and identified environmental and climate variables correlated with breeding occurrence. All available breeding records were collated for nine species of colonially breeding waterbirds: Australian pelican (Pelecanus conspicillatus), great cormorant (Phalacrocorax carbo), pied cormorant (Phalacrocorax varius), white-necked heron (Ardea pacifica), intermediate egret (Ardea intermedia), little egret (Egretta garzetta), straw-necked ibis (Threskiornis spinicollis), glossy ibis (Plegadis falcinellus), and royal spoonbill (Platalea regia). 8

10 Chapter 3: Impacts of water resource development on colonial waterbird breeding The Narran Lakes ecosystem is one of Australia s most important sites for colonial waterbird breeding, holding the largest number of ibis pairs ever recorded. It was Ramsar listed in 1999 for its national and international significance as a major breeding site for the ibis species. It is located in the Condamine-Balonne catchment, which has some of the most extensive water resource development in Australia with over 1,700 GL in storages. Using historical records of breeding and flows, flow modelling and statistical analyses I aimed to determine the impact of water resource development on opportunities for ibis breeding at Narran Lakes. This study also examined the timing and frequency of flows in relation to breeding and current water management policies. Chapter 4: Crisis water management and ibis breeding at Narran Lakes in arid Australia In chapter 4, I examined the most recent breeding event in the Narran Lakes ecosystem in 2008 when, because of declining water levels, a significant volume of water was purchased to ensure that the breeding colony was successful. There was a colony of 74,095 pairs of ibis which bred for the first time in seven years, establishing two contiguous colonies, a month apart. Following cessation of natural river flows, water levels fell rapidly in the colony site, resulting in a crisis management decision by governments for a one-off purchase (AUS$1.87 million) of environmental flow (10,423 ML) to avert mass desertion of the colony. I aimed to examine the reproductive success of each colony in relation to changing water levels, and examine the role of flooding and flow management in ibis breeding and wetland management. 9

11 Chapter 5: Management of environmental flows for colonial waterbird breeding in Australia In this chapter, I reviewed the stimulus and breeding responses of 17 species of colonially breeding waterbirds in Australia with the aim of identifying the key elements for successful breeding. These were examined in relation to the flow regime. This objective is critical in the long-term management of this group of waterbirds because many wetlands and rivers that supply them are regulated by dams and affected by diversions, which have reduced stimuli for breeding. There is an increasing focus on the purchase of environmental flows to restore river systems in the Murray-Darling Basin. One potential target for these flows is the breeding of colonial waterbirds which is highly responsive to flooding. Effective management of environmental flows requires knowledge of the effects of seasonal timing, volume, frequency and duration of flooding that produces successful breeding by colonial waterbirds. Much of this knowledge is scattered and not well focused on the increasing challenge of managing environmental flows for large wetlands where these waterbirds breed. I aimed to bring together the key hydrological variables that are required for successful colonial waterbird breeding and the components of environmental flows that can be used to manage for colonial waterbird breeding. Chapter 6: Conclusion My concluding chapter sums up the contribution of my research to understanding of breeding of colonial waterbirds and their value in terms of measuring environmental flows to key wetlands. My continental analysis show that there are relatively few wetlands that are used as breeding sites for colonial waterbirds and many of the more important ones are vulnerable to the effects of water resource development in the Murray-Darling Basin. There remain gaps in our understanding of how unique key wetland sites are for individual populations of breeding colonial waterbirds; the extent of movement between breeding sites and other wetlands and the fidelity to breeding sites by populations of colonially breeding waterbirds. However there are considerable 10

12 opportunities to collect data to further contribute to our understanding of colonially waterbird breeding. In my concluding chapter suggest future questions that would help to increase this knowledge and also allow managers to use the breeding of colonial waterbirds as an indicator in the management of environmental flows. 11

13 References Brooker, M. G. (1992). Waterbirds of the Macquarie Marshes. Bunn, S. E., Thoms, M.C., Hamilton, S.K., Capon, S,J. (2006). Flow variability in dryland rivers: boom, bust and the bits in between. River Research and Applications 22, Carrick, R. (1962). Breeding, movements, and conservation of ibises (Threskiornithidae) in Australia. CSIRO Wildlife Research 7, CSIRO (2008). Water availability in the Murray-Darling Basin. A report to the Australian Government from the CSIRO Murray-Darling Basin Sustainable Yields Project., 67 pp. Dodman, T., and Diagana, C. (2007). Movements of waterbirds within Africa and their conservation implications. Ostrich 78, Driver, P., Chowdhury, S., Wettin, P., Jones, H. (2004). Models to predict the effects of environmental flow releases on wetland inundation and the success of colonial bird breeding in the Lachlan River, NSW. Paper presented at: 4th Annual Stream Management Conference (Launceston, Tasmania). Dynesius, M., and Nilsson, C. (1994). Fragmentation and flow regulation of river systems in the northern third of the world. Science 266, Frederick, P., Gawlik, D.E., Ogden, J.C., Cook, M.I., Lusk, M. (2009). The White Ibis and Wood Stork as indicators for restoration of the everglades ecosystem. Ecological Indicators 9S, s83-s95. James, C. D., Landsberg, J., Morton, S.R. (1999). Provision of watering points in the Autralian arid zone: a review of effects on biota. Journal of Arid Environments 41, Jenkins, K., Boulton, A.J. (1998). Community dynamics of invertebrates emergeing from reflooded lake sediments: flood pulse and aeolian influences. International Journal of Ecological and Environmental Science 24, Kingsford, R. T. (2000). Protecting or pumping rivers in arid regions of the world? Hydrobiologia 427, Kingsford, R. T., Curtin, A.L., Porter, C.J (1999). Water flows on Cooper Creek in arid Australia determine 'boom' and 'bust periods for waterbirds. Biological Conservation 88,

14 Kingsford, R. T., Curtin, A.L., Porter, J. (1999). Water flows on Cooper Creek in arid Australia determine 'boom' and 'bust' periods for waterbirds. Biological Conservation 88, Kingsford, R. T., Jenkins, K.M., Porter, J.L. (2004). Imposed hydrological stability on lakes in arid Australia and effects on waterbirds. Ecology 59, Kingsford, R. T., Johnson, W. (1998). Impact of water diversions on colonially-nesting waterbirds in the Macquarie Marshes of Arid Australia. Colonial Waterbirds 21, Kingsford, R. T., Roshier, D.A., Porter, J.L. (in press). Australian waterbirds - time and space travellers in a changing landscape. Marine and Freshwater Research in press. Kingsford, R. T., Thomas, R.F. (1995). The Macquaire Marshes in Arid Australia and Their Waterbirds: A 50-year History of Decline. Environmental Management 19, Kingsford, R. T., Thomas, R.F. (2004). Destruction of wetlands and waterbird populations by dams and irrigation on the Murrumbidgee River in Arid Australia. Environmental Management 34, Kushlan, J. A. (1993). Colonial waterbirds as bioindicators of environmental change. Colonial Waterbirds 16, Leslie, D. J. (2001). Effect of river management on colonially-nesting waterbirds in the Barmah-Millewa Forest, South-Eastern Australia. Regulated Rivers: Research and Management 17, Marchant, S., Higgins, P.J., ed. (1990). Handbook of Australian, New Zealand and Antarctic Birds Volume 1 Ratites to Ducks, (Melbourne: Oxford University Press). Mengxiong, C. (1995). Impacts of human activities on the hydrological regime and ecosystems in an arid area of northwest China. In Man's influence on freshwater ecosystems and water use. Proceedings of a Boulder Symposium, IAHS, G. Petts, ed. (Wallingford, Oxon: IAHS Press, Institute of Hydrology), pp Meteorology, B. o. (2010). Drought statement. (accessed 22/03/2010). National Land and Water Resources Audit (NLWRA) (2008) Australian Government National Land and Water Resources Audit. 13

15 Nilsson, C., Reidy, C. A., Dynesius, M. and Revenga, C. (2005). Fragmentation and flow regulation of the world s large river systems. Science 308, Poff, N. L., Olden, J.D., Pepin, D.M., Bledsoe, B.P. (2006). Placing global stream flow variability in geographic and geomorphic contexts. River Research and Applications 22, Poff, N. L., Zimmerman, J.K.H. (2010). Ecological responses to altered flow regimes: a literature review to inform the science and management of environmental flows. Freshwater Biology 55, Puckridge, J. T., Walker, K.F., Costelloe, J.F. (2000). Hydrological persistence and the ecology of dryland rivers. Regulated Rivers: Research & Management 16, Ren, S., Kingsford, R.T., Thomas, R.F. (2009). Modelling flow to and inundation of the Macquarie Marshes in Arid Australia. Environmetrics DOI: /env Taft, O. W., Cowlwell, M.A., Isola, C.R., Safran, R.J. (2002). Waterbird responses to experimental drawdown: implications for the multispecies management of wetland mosaics. Journal of Applied Ecology 39, Thomas, R. F., Kingsford, R.T., Yi, L., Hunters, S.J. (in press). Landsat mapping of inundation ( ) of the Macquarie Marshes in semi-arid Australia. International Journal of Remote Sensing. Young, W. J., Kingsford, R.T. (2006). Flow variability in large unregulated dryland rivers. In Ecology of Desert Rivers, R. Kinsgsford, T., ed. (Cambridge University Press). 14

16 Chapter 2 Colonial waterbirds: wetland use and vulnerability at a continental-scale K. Brandis, D. Ramp and R.T. Kingsford 15

17 Abstract Globally, wetlands are under threat from water resource development and climate change. To assess the vulnerability of wetland dependent species to these threats, it is necessary to understand patterns of wetland use. Colonially breeding waterbirds are amongst the species most at risk due to their reliance on specific wetlands for breeding and their requirement for specific flooding patterns and environmental associations. Opportunities for breeding are particularly reduced by altered river flows and reduced wetland flooding as a result of water resource development but no continental-scale patterns have previously been elucidated, with most research focused on single wetland issues. Using long-term data ( ) we identified wetlands used for breeding by nine species of colonial waterbirds across Australia and identified environmental and climate variables correlated with breeding occurrence. Only <4% of all wetlands were used for breeding, highlighting high specificity. Large colonies (>10,000 birds) were uncommon (<5% of all colonies) and occurred on a limited number of wetlands (n=24). Key variables correlated with breeding occurrence were wetland area, dominant vegetation form and extent of water resource development. Disconcertingly, all of Australia s key colonial waterbird breeding wetlands were within drainage basins that had water resource development. This makes them particularly vulnerable to effects of water resource development as opportunities to breed are reduced. 16

18 Introduction Species that utilise temporally and spatially limited habitats for feeding or breeding are particularly vulnerable to threats (Arthington et al., 2005; Guadagnin et al., 2005; Attum et al., 2009). Temporal variation can be seasonal (Hughes et al., 2009; Hegel et al., 2010), tidal (Raposa et al., 2009) or stochastic (Roshier et al., 2001; Kingsford et al., in press), while spatial variation of aquatic habitats is generally dictated by climate and its relationship with catchment and geomorphological characteristics. Spatially and temporally limited habitats occur across the full range of faunal groups including amphibians (Rodriques et al., 2010) fish (Arthington et al., 2005), birds (Guadagnin et al., 2005), and mammals (Attum et al., 2009). They are particularly prominent in highly variable dryland rivers (Puckridge et al., 1998; Roshier et al., 2002, Young and Kingsford, 2006) where they support flow-dependent organisms such as waterbirds (Kingsford et al., 2010). Among this group, colonially breeding waterbirds use temporally and spatially restricted habitat for breeding (Earnst et al., 1998; Kingsford et al., in press). They breed in colonies of tens to hundreds of thousands of individuals and rely upon availability of specific wetland habitat for this critical stage in their life cycle (Haig et al., 1998). If suitable habitat is not available or conditions are unfavourable, colonial waterbirds may not successfully reproduce (Leslie, 2001; Bechet et al., 2009).Duration of habitat availability is also critical as many colonial species require 3-6 months to raise chicks to fledgling stage (Marchant and Higgins, 1990; Brandis and Kingsford, in press). Flooding and flow characteristics are the major determinants of temporal and spatial habitat availability (Roshier et al., 2001). Given the importance of such habitats, colonially breeding waterbirds may be particularly vulnerable if key wetlands used for breeding are destroyed or degraded. 17

19 Globally, wetlands are under threat due to changes in water supply, either as a result of water resource development (Mengxiong, 1995; Finlayson and Rea, 1999; Owino et al., 2002; Fearnside, 2001) or from climate change (CSIRO, 2008; Kirby et al., 2008; Erwin, 2009). Changes to river flows affect availability of habitat and subsequent opportunities to breed (Taft et al., 2002; Bechet et al., 2009). Water resource development destroys wetland habitat (Thompson, 1978; Kingsford and Thomas, 1995; Finlayson and Rea, 1999; Owino et al., 2002) by reducing flooding of rivers (Stevens et al., 1997; Kingsford, 2000; Poff and Zimmerman, 2010). Impacts of climate change, including changes in rainfall and evaporation can also change river flow regimes (de Wit and Stankiewicz, 2006; Acreman et al., 2009; Erwin, 2009). These threats reduce frequency of waterbird breeding, potentially affecting waterbird populations (Frederick et al., 2009). Australia has an estimated 315,307 km 2 of wetlands (Geodata 1:250,000 Series 3 Topodata, Geoscience Australia), four per cent of the total land area, but relatively few are suitable for colonially breeding waterbirds. Little is known of the full complement of wetlands used by breeding colonial waterbirds across Australia but generally they breed on large inland temporary wetlands and more persistent coastal wetlands (Marchant and Higgins, 1990; Barrett et al., 2003). Much of the continent (70%) is arid and semi-arid (James et al., 1999), with high annual rainfall variability, greater than any other continent (Peel et al., 2001), producing some of the most variable flow river systems in the world (Poff et al., 2006; Young and Kingsford 2006). Colonially breeding waterbirds are highly mobile and are able to establish colonies on spatially and temporally variable flooded habitats (McKilligan, 1975; Frederick et al., 1996). Colonially breeding waterbirds in Australia represent species in four families: Pelecanidae, Phalacrocoracidae, Threskiornithidae, and Ardeidae. These birds are nomadic rather than migratory (Kingsford and Norman, 2002), with movements often triggered by unpredictable rainfall events rather than seasonal changes (Carrick, 1962; 18

20 McKilligan, 1975; Marchant and Higgins, 1990). Australian waterbird breeding varies from seasonal, particularly on the coast and more persistent wetlands, to aseasonal where there is opportunistic breeding following flooding in the more arid regions of Australia (Carrick, 1962; Briggs and Lawler, 1989; Roshier et al., 2001). Colony sizes tend to be smaller on coastal wetlands compared with large inland wetlands which have recorded colonies as large as 800,000 birds (Narran Lakes, 1983) (Marchant and Higgins, 1990, McKilligan, 2005). Some of the large inland wetlands are threatened by water resource development, reducing opportunities for breeding (Kingsford and Thomas, 1995; Kingsford and Johnson, 1998; Brandis et al., in review). This may be exacerbated by changes to rainfall, affecting river flows and increased evaporation caused by climate change (Erwin, 2009). Given the importance of key breeding sites for colonial waterbirds, there is an increasing need to identify characteristics of these breeding sites and their vulnerability to changes in river flows. We aimed to identify breeding sites for nine species of colonial waterbirds across Australia and the vulnerability of these sites to river regulation. We developed breeding models (Morin and Thuiller, 2009) for all nine species, identifying characteristics of wetlands used for breeding. Methods Colonial waterbird breeding This study collated breeding records for nine species of: Australian pelican (Pelecanus conspicillatus), great cormorant (Phalacrocorax carbo), pied cormorant (Phalacrocorax varius), white-necked heron (Ardea pacifica), intermediate egret (Ardea intermedia), little egret (Egretta garzetta), straw-necked ibis (Threskiornis spinicollis), glossy ibis (Plegadis falcinellus), and royal spoonbill (Platalea regia). Our aim was to collate a long term dataset ( ) by collecting every available breeding record for these species. These nine species of colonial waterbirds were colonially breeding species 19

21 distributed throughout Australia inhabiting coastal and inland water bodies for which reasonably good data exist (Marchant and Higgins, 1990). They breed in single or multi species colonies of tens to hundreds of thousands of individuals. These species were chosen to be representative of colonial waterbird breeding including breeding triggers, responses and habitat requirements. Species such as Australian while ibis (T. molucca) were not included due to their predominantly urban habitat distribution and pest status in many parts of eastern Australia (Martin et al. 2007). Other groups including shorebirds and migratory waders were not included in this study due to different movement patterns (i.e. seasonal) and habitat requirements. Vegetation structure is essential in providing breeding platforms. Cormorants, herons and egrets nest in trees along or within rivers and wetlands (Marchant and Higgins 1990), inundated during floods (Leslie 2001). Australian pelicans are ground nesters, usually on sandy islands or beaches (Marchant and Higgins 1990) while ibis and spoonbills nest on emergent macrophytes (Marchant and Higgins 1990; Leslie 2001), including lignum (Muehlenbeckia florulenta) and/or phragmites (Phragmites australis) To identify the characteristics of wetlands that colonial waterbirds used for breeding, in contrast to wetlands where there was no recorded breeding, a geographically referenced dataset of breeding presences and absences was created across Australia. Of 44 data sources of breeding data (Appendix 1), the primary source was the Nest Record Scheme (Birds Australia) Australia s longest running breeding bird survey (1964-ongoing). For each breeding event, we recorded breeding species, wetland name, location, date of breeding, number of individuals and/or nests. Records of no breeding (absences) were collated from The Eastern Australian Aerial Waterbird Survey (Kingsford and Porter 2009). This dataset provided a long-term ( ) record of no breeding on specific wetlands in eastern Australia. Records of absences for other regions of Australia were collated from additional waterbird survey datasets (Halse et al., 1992, 1994, 1995; Jaensch and Vervest, 1990a & b). 20

22 Wetland data Environmental data were collected across Australia to characterize wetlands used for breeding and their suitability for the nine species. A wetland used for breeding was defined as the entire area of the wetland, as there were insufficient data to include area of colonies. Datasets chosen were for variables important to waterbird breeding. They included wetland type, area and perimeter (Roshier et al., 2001; Kingsford and Norman, 2002) (Geodata 1:250,000 Series 3 Topodata, Geoscience Australia). Vegetation type (Vegetation-Post-European Settlement 1988, Geoscience Australia) was also included as an index of available nesting habitat (Briggs and Thornton 1998). Vegetation was re-classified into four groups, based upon the mapped dominant vegetation form in the Vegetation-Post-European Settlement 1988 data layer: trees, shrubs, grasses and no vegetation. Two climate variables (ANUCLIM data; Houlder et al., 2002) were also incorporated: mean annual temperature and mean annual rainfall (Woodall, 1985; Halse and Jaensch, 1989). Wetlands were classified into six mapped categories: floodplain, swamp, lake, watercourse, man-made and estuarine. These categories were derived from the waterbody component of the topographic data layer 1:250,000 scale (Table 1). To identify the extent of water resource development in catchments with breeding sites the size and number of large dams (ANCOLD, 2009) and the volume of water diversions (NLWRA, 2001) were also recorded for each river basin that supplied a wetland. Wetlands were located by surface water management area and drainage basin (Australian Surface Water Management Areas (ASWMA) 2004, Geoscience Australia). As a measure of habitat quality for breeding of each waterbird species, we calculated prevalence of breeding at wetlands (e.g. Goetz et al., 2010): number of times breeding 21

23 occurred ( ). Wetlands were ranked by frequency of breeding. We also calculated the proportion of wetlands with recorded breeding, relative to total wetland habitat available. For each drainage basin, we calculated the area of wetlands used for breeding. Levels of water resource development for each drainage basin were overlayed to assess the potential impact to breeding sites for each species. Table 1. Definition of wetland types and minimum mapping sizes of wetland types used in the model (Geodata 1:250,000 Series 3 Topodata, Geoscience Australia). Wetland type Definition Minimum mapping size (ha) Floodplain Low lying land usually adjacent to lakes or watercourses, which is regularly covered with flood water for short periods Lake A naturally occurring body of mainly static water 6.25 surrounded by land Swamp Land which is saturated with water that is not suitable for agricultural or pastoral use and presents a barrier to free passage Watercourse A natural channel along which water may flow from 62.5 Man-made Estuarine: Foreshore flat time to time A body of water collected and stored behind a constructed barrier for some specific purpose That part of the seabed or estuarine areas between mean high water and the line of lowest astronomical tide Saline coastal flat Marine swamp The nearly level tract of land between mean high water and the line of the highest astronomical tide That low lying part of the backshore area of tidal waters, usually immediately behind saline coast flow, which maintains a high salt water content and is covered with characteristic thick grasses and reed growths Statistical analyses To identify patterns of wetland use by individual species, we examined similarities and groupings among species for the type of wetlands used for breeding and dominant 22

24 vegetation form at breeding sites. We used non-metric multidimensional scaling (nmds) (PRIMER v6; Clarke and Gorley, 2006). Data were standardized to allow for comparisons between species. To determine the types of wetland habitats that were used by different colonially breeding species, a breeding suitability model was developed for each species using the presence/absence breeding and wetland data. Ten predictor variables were identified for inclusion in model selection process: spatial coordinates, mean annual rainfall (mm), mean annual temperature ( 0 C), wetland type, wetland area (ha), wetland perimeter (km), dominant vegetation form, dam capacity (ML), number of dams, and catchment diversions (ML). A Spearman rank correlation of variables found that ) were highly correlated. Only one parameter for each pair was included in the model selection process, choosing the variable for each species which explained most variance. This was done by running a univariate Generalized Additive Model (GAM) using the R statistical environment, Version (R Development Core Team 2010) and package gam (Version 1.0) and extracting pseudo-r 2 values, (calculated as the 1 ), estimating how well each predictive variable alone explained the distribution of a species. To improve normality, dam capacity data were square root transformed, while wetland area, average annual rainfall and catchment diversion data were natural log transformed. To account for spatial patterning and autocorrelation in the breeding wetlands across Australia, a local regression function was used for the spatial coordinates, using a span of This span was identified by running the models for every 0.05 increment of span width and selecting the span with the highest pseudo-r 2. Model selection was then performed for every species by running every model combination of the final eight predictors. For each of the 256 model combinations, 23

25 model performance was evaluated by calculating the Akaike Information Criterion (AIC) (Akaike, 1973) and the final model chosen implementing a trade-off between the fewest numbers of predictor variables, the lowest AIC +2, and the likelihood of the models given the data, computed using Akaike weights. This approach avoids problems inherent in the null hypothesis significance approach that solely relies on significance for variable inclusion (Burnham and Anderson, 2002), and is suited to where both explanatory emphasis and predictive power is warranted. Model performance was assessed by predicting breeding from the final model (modeled data) to the presence/absence data (measured data). Rather than examining performance for a set discrimination threshold, the kappa statistic (a statistical measure of inter-rater agreement; Landis and Koch, 1977; Fielding and Bell, 1997) was computed for 0.05 increments of discrimination and the maximum kappa value obtained. Kappa values of , and respectively indicate fair, moderate and substantial agreement (Landis and Koch, 1977). The deviance explained by each model was also calculated and partial plots for each colonially breeding species showed which explanatory variables were included in each species models and likelihood of breeding. Hierarchical partitioning was performed to identify the contribution of each variable to the model output. Evaluating the influence of predictor variables on a dependent variable in multiple regression is problematic and confounded by multicollinearity, hence we used the method of hierarchical partitioning as recommended by Mac Nally (2000, 2002). Hierarchical partitioning examines all model combinations jointly to identify average influences of predictive variables rather than just from the single best model. Hierarchical partitioning was run using variables included in each species model and conducted using algorithms developed for the R statistical package in library hier.part (Walsh and Mac Nally, 2003). Continental predictive maps of the probability of breeding for each species were then created using the final models for each species. The database of breeding wetlands 24

26 and their environmental characteristics were used to predict the probability that a species would breed on the wetland. Breeding suitability maps were created plotting model fits across all wetlands for each species. For mapping purposes, model fits were smoothed using a kernel density (Spatial Analyst ESRI ArcMap 9.3). Results Colonial waterbird breeding There were 959 records of colonial waterbird breeding in Australia, (Fig. 1; Table 2). Breeding was recorded at 276 unique wetlands, <4% of all named wetlands in Australia (Geoscience Australia Geodata 1:250,000 Series 3 Topodata, Geoscience Australia). Throughout Australia a recorded breeding event for one of the nine species occurred on average once every two years. Most (64%) of the wetlands had only one recorded breeding event, 33% of wetlands had 2-10 recorded breeding events, while only three percent of wetlands recorded >10 recorded breeding events (Fig. 2). Less than six percent of wetlands had recorded breeding by >5 species. Forty-two percent of wetlands recorded between 2-4 species breeding while 52% of wetlands recorded only one species breeding. Ibis breeding accounted for 36% of all records (strawnecked ibis-29%, glossy ibis-7%), followed by cormorants 20% (pied cormorant-12%, great cormorant-8%), egrets 15% (little egret-6%, intermediate egret-9%), royal spoonbill (10%), Australian pelican (10%) and white-necked heron (8%). Only 4.35% of all breeding events recorded 10,000 individuals of a single species; 77.20% of breeding events recorded less than 1,000 individuals of a single species (Fig. 2). Large breeding events ( 10,000 individuals) occurred on only 24 wetlands. Strawnecked ibis bred on average in large same species colonies (~9,000 individuals) while glossy ibis and Australian pelicans bred in same species colonies which averaged ~3,500 individuals. Egret species, cormorant species and royal spoonbills bred on average in groups of between ~1,200-1,700 individuals of the same species (Fig. 2). 25

27 Fig. 1. All recorded colonial waterbird breeding sites ( ) ( ) across drainage basins in Australia: I) North East Coast, II) South East Coast, III) Tasmania, IV) Murray Darling Basin, V) South Australian Gulf, VI) South West Coast, VII) Indian Ocean, VIII) Timor Sea, IX) Gulf of Carpentaria, X) Lake Eyre Basin, XI) Bulloo-Bancannia, XII) Western Plateau, with wetlands from the waterbody layer (1:250,000 scale) in grey (Geoscience Australia 2006). Nineteen percent of Australia s total wetland area was utilized for breeding. The Murray-Darling Basin was the primary basin for colonial waterbird breeding with 44.58% of total wetland area used for breeding (2,467,614 ha) on 139 wetlands (Table 2). Lake Borrie recorded the most number of breeding events (n=22) while Narran Lakes and the Macquarie Marshes recorded the highest diversity with eight breeding species of the nine in this study. 26

28 The distribution of wetlands used by species for breeding was variable across Australia (Fig. 2). All species bred in the Murray-Darling Basin, with ibis and great cormorants breeding predominantly in the Murray-Darling Basin. Australian pelicans also bred in large numbers in the Lake Eyre Basin while spoonbills and the three egret species bred at numerous wetlands in the Timor Sea Basin. White-necked herons also bred in the South West Coast Basin, while the pied cormorant was recorded breeding in all drainage basins (Fig. 2). Lakes (45%) were most frequently used for breeding, followed by floodplains (23%) (Fig. 3). Wetlands dominated by trees (33.87%) or grasses (33.62%) were more commonly used for breeding, followed by wetlands with no-vegetation and shrubs (Fig. 3). Great cormorant, straw-necked ibis and glossy ibis tended to use similar wetland types (Fig. 4a) while there were few obvious groupings among species in relation to dominant vegetation (Fig. 4b). nmds results also showed that these two wetland descriptors (wetland type stress=0.08; vegetation form stress<0.01) identified differences among breeding species (Fig. 4). The distribution of breeding sites for colonially breeding waterbird species was biased towards river basins where there were significant diversions of water, principally the Murray-Darling Basin. Seven of the ten highest ranked wetlands for frequency of colonial waterbird breeding were within the Murray-Darling Basin (Table 3). 27

29 Fig. 2. All recorded breeding sites for nine species of colonially breeding waterbirds ( ), scaled by the largest number of individuals recorded in a single breeding event across the 12 drainage basins: I) North East Coast, II) South East Coast, III) Tasmania, IV) Murray Darling Basin, V) South Australian Gulf, VI) South West Coast, VII) Indian Ocean, VIII) Timor Sea, IX) Gulf of Carpentaria, X) Lake Eyre Basin, XI) Bulloo- Bancannia and, XII) Western Plateau. 28

30 Fig. 2 cont. All recorded breeding sites for nine species of colonially breeding waterbirds ( ), scaled by the largest number of individuals recorded in a single breeding event across the 12 drainage basins: I) North East Coast, II) South East Coast, III) Tasmania, IV) Murray Darling Basin, V) South Australian Gulf, VI) South West Coast, VII) Indian Ocean, VIII) Timor Sea, IX) Gulf of Carpentaria, X) Lake Eyre Basin, XI) Bulloo-Bancannia and, XII) Western Plateau. 29

31 Table 2. Percentage of wetland types used for breeding, total wetland area, and area and number of wetlands used for breeding in each drainage basin i.e. within the Murray-Darling Basin, of total floodplain wetland area (100%) 53.06% were used for breeding (46.94% were not). Drainage Basin Estuarine Floodplain Lake Man made Swamp Watercourse Total wetland area (ha) Breeding wetland area (ha) N North East Coast ,235 9,390 6 South East Coast , , Tasmania ,502 7,765 1 Murray-Darling Basin ,534,713 2,467, South Australian Gulf , South West Coast ,196,328 1, Indian Ocean ,411, Timor Sea ,054, , Gulf of Carpentaria ,368,720 53,883 4 Lake Eyre ,215,537 1,701, Bulloo-Bancannia , , Western Plateau ,330, , Total 31,534,097 5,932,

32 Fig. 3. Proportional use of a) wetland type and b) vegetation form by each of nine species of colonial waterbirds for breeding, across Australia based on all records available ( ). Breeding models Wetland area was the primary variable included in all models with the greatest independent effect (Fig. 5a-i). There was moderate agreement between the model 31

33 outputs and data for all models. Kappa statistics ranged from , while deviance explained by the models ranged from 30.24% % (Table 5). The glossy ibis model included spatial location, wetland area, and mean annual rainfall (Table 5; Fig.5a). Wetland area had the highest independent effect in the model explaining 85% of the deviance compared to rainfall with 15% (Fig. 5a). There was a positive relationship between probability of breeding and wetland area >100 ha (Fig. 5a). There was a negative relationship between probability of breeding and mean annual rainfall with the highest probability of breeding associated with arid zones <500 mm (Fig. 5a). There were four variables in the straw-necked ibis model: spatial location, wetland area, catchment diversions and dominant vegetation form (Table 5; Fig.5b). Wetland area had the highest independent effect in the model of 64%, compared to dominant vegetation from and catchment diversion 18% respectively (Fig. 5b). There was a positive relationship between wetland area and probability of straw-necked ibis breeding. The probability of breeding declined with increasing catchment diversions (Fig. 5b). Higher breeding probability was associated with no vegetation or shrubs (Fig. 5b). The pied cormorant model included the variables spatial location, mean annual rainfall, wetland area, catchment diversions, and dominant vegetation form (Table 5; Fig. 5c). Hierarchical partitioning found that wetland area had the highest independent effect in the model of 62%, dominant vegetation form 34%, and catchment diversions and rainfall <5% respectively. There was a strong positive relationship between wetland area and probability of pied cormorant breeding, with increased probabilities on wetlands >100 ha. Vegetation form was a good determinant of pied cormorant breeding with increased probabilities on no- or low vegetation forms (Fig. 5c). 32

34 Fig. 4. nmds plots showing the similarity among species in relation to wetland types (a) and dominant vegetation (b.) at all breeding sites recorded across Australia ( ). Variables in the great cormorant model included: spatial location, wetland area, dam capacity, and mean annual temperature (Table 5; Fig. 5d). Wetland area had the highest independent effect in the model of 50%, mean annual temperature 30% and dam capacity 20%. There was a positive relationship between the probability of great 33

35 cormorant breeding and wetland area (Fig. 5d). Probability was increased on wetlands >400 ha (Fig. 5d). The relationship with mean annual temperature was generally linear with highest probability occurring in areas with 25 0 C mean annual temperatures (Fig. 5d). The was a slight negative relationship between great cormorant breeding probability and dam capacity, with probability of breeding lower in catchments with large dam capacities (Fig. 5d). Table 3. Highest 10 ranked wetlands by number of recorded breeding, with number of species and largest colonies recorded for each of these wetlands, Wetland Drainage basin Breeding records (yrs) No. of species recorded breeding Largest colony recorded (no. birds) Lake Borrie South-east Coast ,000 Rhyll Swamp South-east Coast ,000 Narran Lakes Murray-Darling ,000 Hird Swamp Murray-Darling ,000 Macquarie Marshes Murray-Darling ,000 Salt Lagoon Island Murray-Darling ,000 Second Reedy Lake Murray-Darling ,000 Booligal Swamp Murray-Darling ,000 Barmah Forest Murray-Darling 9 1 1,700 Dowd Morass South-east Coast 9 1 2,000 The little egret model included spatial location, wetland area, catchment diversions and dominant vegetation form (Table 5; Fig.5e). Hierarchical partitioning found that wetland area had the highest independent effect in the model of 65%, catchment diversions 30% and vegetation form <5% (Fig. 5e). The relationship between wetland 34

36 area and probability of little egret breeding showed increased probability of breeding on both smaller wetlands and very large wetlands (Fig. 5e). These trends may be influenced by the limited number of data points for wetlands at these extreme ends of the scale. There was a negative relationship between the probability of little egret breeding and catchment water diversions (Fig. 5e). There were three variables included in the intermediate egret model: spatial location, wetland area and dominant vegetation form (Table 5; Fig.5f). Wetland area had the highest independent effect in the model of 69%, compared to dominant vegetation from 31% (Fig. 5f). The relationship between wetland area and probability of intermediate egret breeding was generally linear with a slight trend towards increased probability of breeding on larger wetlands (Fig. 5f). There was an increased probability of breeding on small wetlands <100 ha although these were based on few data points (Fig. 5f). Wetland sites with trees and no vegetation as the dominant vegetation from were predictors of intermediate egret breeding (Fig. 5f). Variables included in the Australian pelican model were spatial location, wetland area, mean annual temperature and dominant vegetation form (Table 5; Fig. 5g). Hierarchical partitioning found that wetland area had the highest independent effect in the model of 70%, dominant vegetation form 28% and mean annual temperature 2%. There was an overall positive relationship between probability of Australian pelican breeding and wetland area, particularly on wetlands ,000 ha (Fig. 5g). No vegetation and grasses were the dominant vegetation forms that were associated with increased probabilities of breeding (Fig. 5g). There was a positive relationship between mean annual temperature and probability of Australian pelican breeding, with probabilities increased in regions with mean annual temperatures >17 0 C (Fig. 5g). 35

37 The royal spoonbill model included spatial location, wetland area, dam capacity, mean annual rainfall and catchment diversions (Table 5; Fig.5h). Hierarchical partitioning found that wetland area had the highest independent effect in the model of 68%, mean annual rainfall 30% and dam capacity and catchment diversions <5% respectively. There was an overall positive relationship between the size of wetlands and the probability of spoonbill breeding, probability increased on wetlands >100 ha (Fig. 5h). There were four variables in the white-necked heron model: spatial location, wetland area, dam capacity and catchment diversions (Table 5; Fig. 5i). Wetland area had the highest independent effect in the model of 52%, catchment diversions 25% and dam capacity 23% (Fig. 5i). There was a positive relationship between wetland area and probability of white-necked heron breeding with probabilities increasing on wetlands >100 ha (Fig. 5i). There were negative relationships between probabilities of breeding and both dam capacity and catchment diversions (Fig. 5i). Habitat suitability maps illustrated the predicted distribution of potentially suitable wetlands for each colonial waterbird species based on variables included in the models (Fig. 6). The habitat suitability maps showed the predicted fit of the model for all wetlands across Australia (Fig. 6). Predicted distributions of glossy ibis breeding habitat matched well with recorded wetland areas particularly in the Murray-Darling Basin (Fig. 6). Modelled breeding habitat distributions for straw-necked ibis matched well with recorded wetland sites in the Murray-Darling Basin but did not identify areas in northern Australia where breeding has been recorded (Fig. 6). Pied cormorant predicted breeding habitat distributions were widely distributed, reflecting the distribution of known breeding sites (Fig. 6). Predicted distributions of great cormorant breeding habitat were restricted primarily to the Murray-Darling and South West Coast Basins. This reflected the known wetlands for great cormorant breeding (Fig. 6). Predicted distributions of breeding habitat for little egret closely matched known 36

38 breeding sites (Fig. 6) while predicted breeding areas for intermediate egrets were widely distributed and were not confined to areas of known breeding (Fig. 6). Modelled distributions for the Australian pelican breeding habitat matched areas of known breeding, particularly in the Murray-Darling and Lake-Eyre Basins (Fig. 6). Royal spoonbill and white-necked heron breeding habitat distributions closely matched known wetland sites (Fig. 6). Discussion Few wetlands (<4%) were used by colonial waterbirds for breeding across Australia and most of these (77.20%) supported small colonies (<1,000 individuals) of single species. Only 18 wetlands across the continent had more than five species that bred together and there were also few (<5%) wetlands that supported large breeding events (>10,000 individuals). This highlights the importance of only a limited number of wetlands for the breeding of colonial waterbirds. Colonially breeding species require considerable resources to raise chicks in large colonies and there are probably relatively few wetlands that provide sufficient food and nesting resources. Some wetlands were also used frequently for breeding by colonial waterbirds (Table 3), which may similarly reflect the quality of nesting habitat and supplies of food resources (Goetz et al. 2010). This may also reflect fidelity to traditional wetlands by some species. Site fidelity is thought to be advantageous to birds as they have a prior knowledge of resources and risks (Renken and Smith 1995). If site fidelity is a wetland use strategy used by colonial waterbirds it increases species vulnerability to changes in wetland habitat. 37

39 Table 4. Water resource development and numbers of unique wetland sites used by each of nine colonially breeding species in each drainage basin. Drainage Basin Diversions Dam Capacity (ML) a (ML) b No. pelican sites No. white-necked heron sites No. spoonbill sites No. glossy ibis sites No. straw-necked ibis sites No. intermediate egret sites No. little egret sites No. egret unknown spp. sites No. great cormorant sites No. pied cormorant sites Total no. wetlands used for colonial waterbird breeding a North-East Coast 2,190, , South-East Coast 1,283,468 5,423, Tasmania 3,389,168 4,922, Murray-Darling Basin 11,791,360 28,977, South-Australian Gulf 143, South-West Coast 371, , Indian Ocean 12,409 0 Timor Sea 317,098 6,315, Gulf of Carpentaria 51, , Lake Eyre Basin , Bulloo-Bancannia Western-Plateau 1, Australia total 19,553,082 46,769, a NWLRA, 2001 b ANCOLD

40 Table 5. GAM model results for nine species of colonially breeding waterbirds, using data across Australia, showing variables included in each of the models and significance (*). Vegetation form results relative to reference level = bare. Overall model performance measured by Kappa and deviance explained. Species Variable Estimate S.E Z-value P-value Kappa Deviance explained % Glossy ibis Intercept Longitude * Latitude Wetland area <0.001* Rainfall Straw-necked ibis Intercept * Longitude Latitude <0.001* Wetland area <0.001* Diversions Grasses Shrubs Trees Pied cormorant

41 Species Variable Estimate S.E Z-value P-value Kappa Deviance explained % Intercept Longitude Latitude Rainfall Wetland area <0.001* Diversions Grasses * Shrubs Trees <0.001* Great cormorant Intercept Longitude Latitude Wetland area <0.001* Dam capacity Temperature Little egret Intercept

42 Species Variable Estimate S.E Z-value P-value Kappa Deviance explained % Longitude Latitude Wetland area Diversions * Grasses Shrubs Trees Intermediate egret Intercept Longitude Latitude Wetland area Grasses Shrubs Trees Australian pelican Intercept <0.001* Longitude

43 Species Variable Estimate S.E Z-value P-value Kappa Deviance explained % Latitude <0.001* Wetland area <0.001* Temperature * Grasses Shrubs * Trees * Royal spoonbill Intercept <0.001* Longitude * Latitude * Wetland area <0.001* Dam capacity Rainfall <0.001* Diversions * White-necked heron Intercept Longitude * Latitude <0.001* 42

44 Species Variable Estimate S.E Z-value P-value Kappa Deviance explained % Wetland area * Dam capacity Diversions

45 Fig. 5a. Partial plots for breeding by glossy ibis of modelled relationships between explanatory variables included in the model and likelihood of breeding and hierarchical contribution of each significant variable plot (histogram) showing relative of each variable to the model output. 44

46 Fig. 5b. Partial plots for breeding by straw-necked ibis of modelled relationships between explanatory variables included in the model and likelihood of breeding and hierarchical contribution of each significant variable plot (histogram) showing relative of each variable to the model output. 45

47 Fig. 5c. Partial plots for breeding by pied cormorant of modelled relationships between explanatory variables included in the model and likelihood of breeding and hierarchical contribution of each significant variable plot (histogram) showing relative of each variable to the model output. 46

48 Fig. 5d. Partial plots for breeding by great cormorant of modelled relationships between explanatory variables included in the model and likelihood of breeding and hierarchical contribution of each significant variable plot (histogram) showing relative of each variable to the model output. 47

49 Fig. 5e. Partial plots for breeding by little egret of modelled relationships between explanatory variables included in the model and likelihood of breeding and hierarchical contribution of each significant variable plot (histogram) showing relative of each variable to the model output. 48

50 Fig. 5f. Partial plots for breeding by intermediate egret of modelled relationships between explanatory variables included in the model and likelihood of breeding and hierarchical contribution of each significant variable plot (histogram) showing relative of each variable to the model output. 49

51 Fig. 5g. Partial plots for breeding by Australian pelican of modelled relationships between explanatory variables included in the model and likelihood of breeding and hierarchical contribution of each significant variable plot (histogram) showing relative of each variable to the model output. 50

52 Fig. 5h. Partial plots for breeding by royal spoonbill of modeled relationships between explanatory variables included in the model and likelihood of breeding and hierarchical contribution of each significant variable plot (histogram) showing relative of each variable to the model output. 51

53 Fig. 5i. Partial plots for breeding by white-necked heron of modeled relationships between explanatory variables included in the model and likelihood of breeding and hierarchical contribution of each significant variable plot (histogram) showing relative of each variable to the model output. 52

54 Fig. 6 Modelled breeding areas across Australia for each colonial waterbird species. Measure of model fit is illustrated using graduated grey scale, white - light grey showing areas of low model prediction while darker grey areas show areas of higher model prediction. 53

55 Fig. 6 cont. Modelled breeding areas across Australia for each colonial waterbird species. Measure of model fit is illustrated using graduated grey scale, white - light grey showing areas of low model prediction while darker grey areas show areas of higher model prediction. 54

56 The Murray-Darling Basin was the dominant region for wetlands used by colonially breeding waterbirds in Australia with 46% (n=139) of all wetlands used for colonial waterbird breeding on over half of the available floodplain habitats (Table 2). This was the only river basin in Australia where all nine species were recorded breeding (Table 4). Also this was the basin with the largest colonies (Fig. 2 and Table 3). The Murray- Darling Basin is also Australia s most regulated drainage basin, with the greatest number of diversions and dam storage capacity (Table 3, NLWRA 2001; ANCOLD 2009). This makes colonially breeding waterbirds particularly vulnerable to effects of river regulation. Impacts from water resource development have been recorded at several key breeding sites in the Murray-Darling Basin. In the Macquarie Marshes, colony sizes, species abundance, species diversity and breeding frequency have all been reduced following reductions in flows (Kingsford and Thomas 1995; Kingsford and Johnson 1998). Similar impacts have also been reported in the Lowbidgee (Kingsford and Thomas 2004) and the Barmah-Millewa Forest (Leslie 2001) The key wetland sites in Australia for colonial waterbird breeding, based on frequency of use, species diversity and colony sizes were Narran Lakes (16 years with breeding; 8 breeding species, 5 events >10,000 birds), and the Macquarie Marshes (13 years with breeding; 8 breeding species, 8 events >10,000 birds). Other important sites included Booligal and Second Reedy Lake (Table 3). All the major sites for breeding waterbirds in the Murray-Darling Basin are threatened by water resource development. The Timor Sea Basin, the second most important with regards to number of waterbird breeding sites also had the second highest dam storage capacity in Australia (Table 4). All drainage basins had some level of water diversion while only four have no large dams (Table 4). This highlights the extent of water resource development across all regions of Australia. 55

57 Wetland sites that provide frequent opportunities for breeding for numerous species in large colonies are important in contributing to the maintenance of waterbird populations on a continental scale. If their value as breeding sites is reduced as a result of water resource development, the impact on waterbird populations may be catastrophic, impacting on the long term viability of species. Temporary floodplain wetlands, such as floodplains and some lakes, which form the primary breeding habitat for colonial waterbirds are particularly vulnerable to reductions in flow and changes to the flow regime, either as a result of water resource development. Water resource development measured by diversions and dam capacity was a determining variable in the models for six species models (pied cormorant, great cormorant, white-necked heron, royal spoonbill, straw-necked ibis, and little egret) (Fig. 5 a-i). In general, probability of breeding decreased with increased dam capacity or diversions. Assessing potential risks to species, ecosystems and ecosystem services (Jiguet et al. 2010) is crucial for conservation planning and policy development. We identified characteristics of wetlands used for breeding by colonial waterbirds across Australia, enabling an assessment of risk to wetlands and waterbird populations from water resource development. Our breeding niche models identified which variables were associated with breeding habitat of each species. This enabled the mapping of potential breeding wetlands across Australia for each species allowing for an improved understanding of the spatial distribution of breeding habitat for each species. Wetland area was a key variable for all species in determining the probability of breeding (Fig. 5a-i). Relationships were generally positive with a positive association between probabilities of breeding and wetland size (Fig.5a-i) (Paszkowski 2006; Guadagnin et al. 2009). Dominant vegetation form was an important determining variable for five species (intermediate egret, little egret, straw-necked ibis, pied-cormorant and Australian pelican). This may reflect more specific nesting requirements for these species. 56

58 Identification of key breeding sites and characteristic variables were dependent on data collected for breeding over a long period of time. These have inherent bias against the reporting of breeding on inland wetlands that are remote from human communities. Recently there have been comprehensive surveys of waterbird breeding in the Lake Eyre Basin (Reid, J. pers. comm.) and across Australia (Porter, J. pers. comm.) which will contribute proportionally more breeding records for more remote wetland areas reducing the bias towards wetlands near populated areas. There were also limitations in models. Breeding records were collated from a range of different data sources, utilizing a variety of survey techniques and objectives. Records of breeding may have been incidental to the primary survey aim and may lack comprehensive recording of species. Records of breeding may also reflect proximity to population centres, under representing remote wetlands. There may also be a few missing records of breeding, despite our best efforts. Also national explanatory data sets were necessarily at a coarse scale which may not adequately represent the critical variables of importance for waterbird breeding. Further, breeding niche models developed did not include a temporal component to the frequency of use of wetlands for breeding. The incorporation of a temporal component would provide information regarding the relative importance of breeding sites and changing patterns of use. Also, the data used in model development was limited to presence or absence and did not account for sizes of breeding events. Finally, there was potentially an over estimation of suitable wetland sites in the South-west and Indian Ocean Basins, relative to the available breeding data and due to a lack of absence data points. This is the first continental scale analysis of breeding of colonial waterbirds in Australia. We found that there were relatively few wetlands that were important in terms of frequency of breeding and number of breeding pairs and most of these were in the Murray-Darling Basin where they are highly vulnerable to the impacts of water resource development. Breeding habitat models indicated that other wetland areas 57

59 may exist that are suitable for breeding of colonial waterbirds and there is a need to identify whether these areas are true breeding sites or artifacts of a modeling process that is highly dependent on coarse scale environmental data. Acknowledgements This study was supported by the Australian Wetlands and Rivers Centre at the University of NSW. 58

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69 Kingsford, R. T., Bedward, M., Porter, J. (1994). Wetlands and Waterbirds in Northwestern NSW. Occasional Paper No. 19. NSW National Parks and Wildlife Service Kingsford, R. T., Curtin, A.L., Porter, C.J (1999). Water flows on Cooper Creek in arid Australia determine 'boom' and 'bust periods for waterbirds. Biological Conservation 88, Kingsford, R. T., Porter, J.L. (1999). Wetlands and waterbirds of the Paroo and Warrego rivers. In A Free Flowing River: The ecology of the Paroo River, R.T. Kingsford, ed. (Hurstville: NSW National Parks and Wildlife Service), pp Kingsford, R. T., Auld, K. (2003). Waterbird breeding in the Macquarie Marshes - a guide to river health. Final report Kingsford, R. T., Auld, K. M. (2005). Waterbird breeding and environmental flow management in the Macquarie Marshes, Arid Australia. River Research and Applications 21, Kingsford, R. T., Brandis, K., Porter, J.L. (2008). Waterbird response to flooding in the northern Murray-Darling Basin Final Report December 2008, (UNSW) Lane, B. (1984). Report on a trip to Lake Eyre North, 20th - 24th September, Royal Australasian Ornithologists Union Lane, J. A. K., Pearson, G.B., Clarke, A.G. (1997). Waterbird use of Peel-Harvey Estuary following opening of the Dawesville Channel in April 1994: Progress Report. WA Department of Conservation and Land Management Ley, A. J. (1998). The response of Waterbirds to the 1997 Flood in the Narran Lake Nature Reserve, New South Wales. Australian Bird Watcher 17, Llewellyn, L. C. (1983). Movements of Cormorants in South-eastern Australia and the influence of floods on breeding. Australian Wildlife Research 10, Maddock, M. (1986). Fledgling success of Egrets in dry and wet seasons. Corella 10, Magrath, M. J. L., Wettin, P.D., Hatton. P.J. (1991). Waterbird Breeding in the Booligal Wetlands 1989, Background, and Guidelines for Water Management of Future Colonies. TS91.075, Department of Water Resources Technical Services Division Magrath, M. J. L. (1992). Waterbird Study of the Lower Lachlan and Murrumbidgee Valley Wetlands in 1990/91, New South Wales Department of Water Resources 68

70 McCosker, R. O. (1996). Gwydir Wetlands: Ecological Response to Flooding LANDMAX Natural Resource Management Services McKilligan, N. G. (1975). Breeding and movements of the straw-necked ibis in Australia. Emu 75, Smith, J. (1993). A Report in the Vertebrate Fauna of the Narran River Floodplain, N.S.W. NSW National Parks and Wildlife Service Spencer, J. (2008). Gwydir waterbird and fish habitat study: final report on historical records of waterbirds and fish populations in the Gwydir wetlands. In NSW Wetland Recovery Program, (Rivers and Wetlands Unit, NSW Department of Environment and Climate Change.). Waterman, M., Close, D., Condon, D. (1971). Straw-necked Ibis (Threskiornis spinicollis) in South Australia: Breeding colonies and movements. The South Australian Ornithologist 26, 7-11 Waterman, M. H., Read, J.L. (1992). Breeding success of the Australian Pelican Pelecanus conspicillatus on Lake Eyre South in Corella 16,

71 Chapter 3 Impacts of water resource development on colonial waterbird breeding Brandis, K., Kingsford, R.T., Ren, S., and D. Ramp Ecological Applications (in review) 70

72 Abstract There is a global need to measure the effects of water resource development on species reliant on wetlands for critical stages of their life cycles. Without such knowledge, water resource developments will continue to be poorly assessed for ecological consequences. Assessment is difficult because consequences are usually realised over long periods, particularly in dryland systems. We used hydrological modelling to estimate impacts of water resource development on Australia s most important ibis breeding site, Narran Lakes, in the Murray-Darling Basin. Water resource development during the 1990s reduced median annual flows by 76%. To identify impacts on ibis breeding at Narran Lakes, we used recorded ibis breeding events ( ) and simulated long-term impacts of regulation by modelling river flow ( ) under pre-1990 and post-1990 development conditions. We estimated that reductions in total annual flow volume would decrease opportunities for ibis breeding on large flow events by 30% and change the frequency of breeding from once every four years to once in 43.5 years. Also, current water management rules for waterbird breeding (April-August) do not coincide well with the timing of flow events or the majority of breeding events (54%) occurring in December February. These significant impacts of water resource development on ibis breeding may have implications for long-term species survival and the status of the Narran Lakes system as a wetland of international importance. River development should account for considerable lags in ecological impacts which can be identified through modelling flow linked to ecosystem responses. Identification of such impacts is critical for global rehabilitation of wetlands and their dependent organisms and for protection of systems not yet developed. 71

73 Introduction Many of the world s most significant wetlands on dryland rivers are degrading as a result of the development of water resources, primarily for irrigation (Lemly et al. 2000, Coe and Foley 2001, Kingsford et al. 2006). Regulation of rivers and diversion of water upstream has denied wetland systems of essential inundation patterns that trigger ecological responses (Maltchick and Medeiros 2006). All ecosystems organisms and processes are affected (Kingsford 2000a, Bunn and Arthington 2002, Katano et al. 2009, Mallik and Richardson 2009), with effects potentially exacerbated where critical life history stages are particularly dependent on natural flow regimes. Waterbirds are a group of aquatic organisms that are highly dependent on wetland function (Kushlan 1993) with changes in communities often reflecting effects of water resource development (Kingsford and Thomas 2004, Kingsford et al. 2004a, Frederick et al. 2009). They also depend on sufficient rainfall or river flows for successful breeding (Kingsford and Norman 2002, Taft et al. 2002). Colonially breeding waterbirds are particularly responsive to widespread inundation, setting up large colonies soon after inundation (Schogolev 1996, Earnst et al. 1998, Leslie 2001, Kingsford and Auld 2005). Decreasing flow inundation frequency and extent can cause declines in waterbird breeding and reproductive success impacting on waterbird populations (Crozier and Gawlik 2003, Frederick et al. 2009). Impacts of water resource development on waterbirds and wetlands are widespread. Declines in waterbird abundance in the Rift Valley, Kenya occurred with expansion of irrigated agriculture (Owino et al. 2000). In the United States, waterbird species assemblages changed following construction of dams on the Colorado River (Stevens et al. 1997). Declines in colonial waterbird populations during the 1970s on the Mississippi River, were associated with water resource development (Thompson 1978). In Australia, the building of dams and diversion of water for irrigation has decreased 72

74 the size and frequency of events of breeding of colonial waterbirds in the Murray- Darling Basin (Fig. 1; Kingsford and Johnson 1998, Leslie 2001, Buchanan 2009). Many rivers in the Murray-Darling Basin are severely impacted by upstream water resource development (Kingsford 2000a), affecting much of the more than four million hectares of wetlands across the Murray-Darling Basin (Kingsford et al. 2004b). The most recently developed river is the Condamine-Balonne in the northern Murray- Darling Basin (Fig. 1). Upstream water resource development began in the 1950s and 1960s when flows from the Condamine-Balonne River were altered by small scale irrigation. In 1972, Beardmore Dam (81,700 ML) was built by the Queensland Government, sponsoring the St George Irrigation Scheme supplying 134 km 2 of irrigated crops (ANCOLD 2009). This was a catalyst for the expansion of irrigation downstream of St George on the Lower Balonne floodplain (Fig. 1), through the development of large private irrigation storages (>1,500,000 ML, CSIRO 2008a) during the 1980s and 1990s (Kingsford 2000b, Thoms and Parsons 2003, CSIRO 2008a). The flows from the river are now among the most significantly altered in the Murray- Darling Basin with an average of 53% of natural flows extracted upstream of the end of the river (CSIRO 2008b). The Condamine-Balonne supplies a large deltaic floodplain of >1.4 million hectares (Kingsford et al. 2004b), including a terminal lake system, Narran Lakes. This was the site of the largest ibis breeding colony ever recorded in Australia in 1983 (400,000 pairs, Marchant and Higgins 1990). The Narran Lakes continue to regularly support large concentrations of breeding ibis (>10, ,000 breeding pairs) (Beruldsen 1985, Brooker 1993, Ley 1998a, 1998b, Brandis and Kingsford in press). The Narran Lakes system was listed as a Ramsar site in 1999, primarily because of its value as breeding site for breeding ibis (Ramsar 1999). Given the increasing upstream water resource development, there is considerable concern about changes to the frequency of ibis breeding in the Narran Lakes ecosystem and future management of this important wetland for conservation of 73

75 organisms, including colonially breeding waterbirds. A key focus for river management and delivery of environmental flows is to ensure successful breeding of ibis (Brandis and Kingsford in press) and yet relatively little is known about amount of water required to initiate breeding or the effects of upstream water resource development on ibis breeding. Two critical measures of ibis breeding: the timing of breeding and the quantity of water required for successful breeding are largely unknown and yet management targets are specified for river management by the upstream state of Queensland (QLD ROP 2007). Using measured data over a relatively short time period ( ) we identified thresholds of flow that stimulate ibis to breed on the Narran Lakes system. Then, using long term flow data ( ) and LOESS modelling we examined the effects of upstream development of water resources on breeding frequencies. We also investigated the timing of breeding of ibis in relation to current management targets for ibis breeding. Materials and Methods Study Site The Narran Lakes ecosystem (30,000 ha, Fig. 1), consists of three lakes, Back Lake, Clear Lake and Narran Lake, a large area of floodplain and the main channel of the Narran River. The ecosystem relies primarily on flows from upstream within the Condamine-Balonne River (catchment area 143,900 km 2 ). The Condamine-Balonne River flows into the deltaic system consisting of four rivers (Thoms and Parsons, 2003): Birrie, Bokhara, Culgoa and Narran (Fig. 1). These supply the Lower Balonne floodplain which is shared almost equally between the states of Queensland and New South Wales even though 84% of the catchment lies in Queensland (Fig. 1; Kingsford et al., 2004b). 74

76 Waterbird breeding Three species of ibis breed with sufficient flooding from flow or local rainfall, predominantly straw-necked ibis (Threskiornis spinicollis) but also small numbers of glossy ibis (Plegladis falcinellus) and Australian white ibis (Threskiornis molucca) (Ley, Fig.1. The rivers of the Condamine-Balonne catchment in eastern Australia, in the northern Murray Darling Basin (stippled area), flowing between from the state of Queensland (QLD) in the north to New South Wales (NSW) in the south, showing locations of rainfall stations ( ) 1. Woodlands, 2. Karoola Park, 3. Weribone, 4. Dirrinbandi High School, 5. New Angeldool, 6. Grawin Opal Fields, 7. Walgett and 8. Brewarrina and river flow gauges ( ) A. St George, B. New Angeldool, and C. Wilby Wilby. 75

77 1998a). Colonies of ibis establish when there is sufficient flow in the Narran River, followed by widespread flooding of the Narran Lakes ecosystem, all of which depend on water from upstream in the catchment. We identified all breeding events of ibis from the earliest recorded observation to present ( ) in the Narran Lakes ecosystem, from scientific reports (Beruldsen, 1985; Ley, 1998a, 1998b; Ley, 2003; Brooker, 1993), unpublished records (Henderson, 1999a, 1999b, 1999c; Magrath, 1991; Smith 1993) and personal observations (Maher M. pers. comm.; Kingsford, R.T.). Recording of observations of breeding (ad hoc observations, ground and aerial surveys) began in 1971 but this tended to be variable and opportunistic as Narran Lakes was privately owned until 1988 when it was declared a nature reserve. There were no protected area managers at Narran Lakes until it was declared a reserve in 1998 but even after this there was not always a permanent person on site recording breeding data. As a result, there may be been breeding events that were not recorded. Since 2008 the conservation agency has rigorously collected data on the breeding of colonial waterbirds. Despite this, there is a reasonable record of breeding events because of the importance of the area for the breeding of colonial waterbirds (Beruldsen, 1985; Ley, 1998a, 1998b, 2003). To identify the size of flow events that stimulated ibis breeding, we used total daily flow volumes from the Wilby Wilby gauge on the Narran River (Fig. 1), with analyses to determine thresholds for breeding based on data collected ( ). The Narran River is highly ephemeral with long periods of no flow. For this analysis, we defined flow events when total daily flow volumes exceeded 100 ML at the Wilby Wilby gauge: the minimum flow required to reach Narran Lakes 90 km downstream (Rayburg, S. pers. comm.). Completion of an event was when total daily flow volume fell below 100 ML and continued to zero. Where daily flow fell below this point, but not to zero, and then exceeded 100 ML, all subsequent flows were included in the flow event, until zero was reached. We calculated total flow volume, mean daily flow and flow duration for each event. Flow duration reflected inundation duration and habitat availability for 76

78 successful ibis breeding which requires 3-5 months of inundation (Leslie, 2001; Marchant and Higgins 1990). We tested for differences in the characteristics (total volume, mean daily flow and flow duration) of flow events that stimulated breeding and those that did not (t-test; SPSS Statistics 17), recognising that periods of no flow were omitted. Flow data were log transformed to improve normality. We also investigated seasonality of breeding by identifying the month breeding began and the month that flow reached Wilby Wilby for each recorded breeding event. We used classification and regression tree (CART) analyses (Breiman et al., 1984) in R (R Development Core Team, 2009) to identify flow thresholds that stimulated breeding of ibis. CART is a non-parametric statistical method requiring no assumptions about the underlying distribution and which splits data on the basis of an exhaustive search of all possibilities to produce a classification tree. Thresholds were identified for three hydrological variables, total event volume (ML), mean daily flow (ML) and flow duration (days). This classification produced errors of commission (above threshold but no breeding) and omission (below threshold but breeding). To examine the relationship between total annual flow, regulation, and time since last breeding on breeding by ibis, we built a binomial generalised linear model (GLM) within R. An examination of breeding events using the auto-correlation function (ACF in the nlme library in R) indicated negative temporal autocorrelation four to five years after breeding (ACF=-0.3). With breeding as our binary response, we used total annual flow and time since last breeding (in years) as continuous variables and regulation (pre- or post-1990) as a factor. The 1990 cut-point was based on the considerable water resource development that occurred after 1990 (Kingsford, 2000b; Thoms and 77

79 Parsons, 2003). Temporal autocorrelation in the model residuals were examined to determine whether any patterning remained. Large local rainfall events (>~300 mm) can also flood parts of the Narran Lakes ecosystem and stimulate ibis breeding (Terrill, P. pers comm.). To determine whether there were any local rainfall events that were of sufficient magnitude to stimulate breeding in the Narran Lakes ecosystem, we analysed local monthly rainfall, from Walgett, 80km to the east and Brewarrina, 65 km west (Fig. 1) for the period when records for both stations were available. The stations were significantly positively correlated (p<0.001, R 2 =0.606, n=401). Effects of water resource development The Narran Lakes ecosystem floods predominantly from river flows from the upper catchment (Fig. 1). Heavy rainfall in the mid to upper catchment (Karoola Park (Fig. 1) mean annual rainfall=542 mm, ±SD=156; n=51) produces large floods during the summer, and occasionally spring (Bureau of Meteorology, 2008) with flows occasionally supplemented by local rainfall in the lower catchment (Grawin Opal Fields (Fig. 1) mean annual 419 mm, ± SD=157, n=5 years). To identify potential changes to waterbird breeding at Narran Lakes, we examined changes to flow to the Lower Balonne floodplain and specifically Narran Lakes ecosystem in the period before ( ) and after ( ) when there was significant development on the Lower Balonne river system. We developed two flow models, hereinafter called pre-1990 and post-1990 for these time periods, for the Narran River using daily rainfall and flow data. We used all available daily flow data from three gauges: St George ( ), New Angeldool ( ) and Wilby Wilby ( ) (Fig. 1). Daily flow data were transformed to annual data calculated 78

80 for the twelve month period November October. This period ensured that predominant summer flows (December-February) were captured within a particular year. To incorporate the effects of local rainfall on flow, we also used rainfall data from five locations on the Lower Balonne floodplain, downstream of St George: Woodlands ( ), Karoola Park ( ), Weribone ( ), Dirranbandi High School ( ) and New Angeldool ( ) (Fig. 1) (Bureau of Meteorology, 2008). Missing data in the rainfall records were interpolated from nearby rainfall stations. All rainfall stations had similar low mean annual rainfall but with high variability: Weribone 525 mm (±SD=152, n=87), Woodlands 490 mm (±SD=143, n=87), Karoola Park 539 mm (±SD=142, n=87), Dirrinbandi High School 470 mm (±SD=163, n=87) and, New Angeldool 465 mm (±SD=172, n=87). Flow models were developed sequentially, using annual flow and rainfall data for the three flow gauges (Fig. 1). All models were developed using a local polynomial regression fitting (LOESS) function (Cleveland et al., 1988) and leave-one-out samples in R language (R Development Core Team, 2009; Ren et al., 2009). The first model developed was for St George, using flow data, which incorporated flows originating in the upper catchment and rainfall from Woodlands, Karoola Park and Weribone, accounting for locally generated flows (Fig. 1). We modelled the relationship between flow and rainfall pre-1990 and then used this model to forecast flows in the period as if no development had occurred. We also developed a separate model for post development (post-1990; ) and hindcast this model to the period before 1990 as if development had occurred over the longer time period. We then developed separate downstream sequential models for New Angeldool and Wilby Wilby for pre-1990 and post-1990 development, based on the flow models for St George (Ren et al., 2009). Similar models for New Angeldool used measured flow data from New Angeldool and St George and rainfall data from Dirranbandi High School, while Wilby Wilby models ( ) used flows from Wilby Wilby and New 79

81 Angeldool and rainfall data from New Angeldool (Fig. 1). All models were compared using the corresponding medians and 95% quantile confidence intervals. Due to the difficulty in determining water resource development impacts in such a highly variable system over a short time period, we used the results from the Wilby Wilby pre-1990 flow model for the full period of rainfall records ( ) and compared this model to the post-1990 Wilby Wilby flow model. This incorporated variability over 87 years which is particularly important in such highly variable systems. We focused on the flows that stimulated breeding of ibis through CART analysis. In addition, we examined frequency of breeding events pre-1990 and post-1990 development. We assessed changes in flow and opportunities for breeding on a decadal time period to identify periods of potentially greater impact. T-tests were performed to assess the significance of these changes. Results Waterbird breeding There were 58 flow events over 38 years ( ), producing 15 recorded ibis breeding events (Fig. 2). There were significant differences between the size of the flow events (t=-6.27, df = 56; p<0.001), mean daily flows (t=-6.533, df=56, p <0.001) and flow duration (t=-4.817, df=56, p<0.001) that stimulated recorded breeding events and those that did not. Recorded ibis breeding events were associated with thresholds for three flow measures based on CART analyses: total flow event volumes >100,012 ML, mean daily flows >1,552 ML, and flow durations >63 days at Wilby Wilby. Flow events that resulted in recorded breeding but were below CART identified thresholds for two measures were: November-December 2000 (total flow 45,931 ML, flow duration 27 days) and December 2007-March 2008 (total flow 59,593 ML, mean daily flow 609 ML). There were a further three flow events that resulted in breeding, below one flow measure: May-December 1978 (mean daily flow 728 ML), February-March 80

82 1997 (flow duration 46 days) and May-October 1998 (mean daily flow 1,175 ML). Also there was no recorded breeding for three flow events, February June 1977, December 1981-April 1982 and February-April 1994 which met two of the three hydrological thresholds (Fig. 2). The 1977 and 1982 flow events exceeded the total event flow and duration thresholds but were below the mean daily flow threshold (1,541 and 1,139 ML respectively). The 1994 flow event exceeded the total flow event and mean daily flow threshold but was only 52 days in duration. While a more conservative approach would have been to exclude these data points we predicted that given the flow characteristics and seasonal timing of the flows, that ibis breeding would have probably occurred during these flow events in 1977, 1982, and 1994 (Fig. 2) but were not recorded; these times coincided with periods when there was relatively little visitation at the site. We subsequently included these events as breeding events and re-ran the CART analysis using only total annual flows. Total annual flows were useful because they allowed us to link to total flow volumes modelled over time. As a result, we identified an annual flow threshold for breeding of 160,183 ML at Wilby Wilby as the trigger for breeding. All annual flows larger than this threshold (n= 12) resulted in ibis breeding. There were 25 annual flows smaller than this threshold; five of which resulted in ibis breeding. The lowest recorded annual flow that initiated breeding was 46,782 ML (2001). There was only one local rainfall event that may have been of sufficient magnitude to stimulate ibis breeding: February 1976 (mean= 406 mm) but this coincided with a flow event and ibis were already recorded breeding. There was high seasonality to flow events with 54% of all flow events occurring during December-February (summer), 30% during March-May (autumn), 9% during September-November (spring) and only 7% during June-August (winter) (Fig. 3). Breeding events were also tied to flow events of a certain magnitude and so breeding 81

83 was also highly seasonal, with 58% occurring in December-February, 32% in March- May, and 10% in September-November (Fig. 3). Fig. 2. Flow events at Wilby Wilby on the Narran River, upstream of the Narran Lakes ecosystem, showing recorded breeding events (*) and probable breeding event (+) at Narran Lakes, based on subsequent analyses ( ). Horizontal line A shows the CART breeding-flow event threshold (100,012 ML) while line B shows the lowest flow event with recorded breeding (45,931 ML). Total annual flow, regulation and time since last breeding plus interaction terms explained 55.4% of the variability in Ibis breeding at Narran Lakes (Table 1). Only total annual flow was significant at the 0.05 level. Examination of the model residuals showed that patterns associated with temporal autocorrelation were no longer present. No significant interaction between regulation and flow or time since last breeding was detected in our model. 82

84 Fig. 3. Total number of flows originating in each month (hollow bars) and number of ibis breeding events originating during each month (black bars) Table 1. Results of binomial GLM examining the relationship between total annual flow, regulation and time since last breeding on breeding by ibis. Deviance explained 55.4%. Model variables Estimate SE Z-value p-value Intercept Flow * Regulation Time since last breeding Regulation* Flow Regulation* Time since last breeding

85 Effects of river regulation Our flow models for pre-1990 and post-1990 closely matched actual flow data at the three gauges: St George, New Angeldool and Wilby Wilby for the period 1921 to 2008 (Table 2). There were no significant differences between the observed and predicted distributions of flows pre-1990 at St George, New Angeldool or Wilby Wilby (Table 2). Medians and 95% quantile confidence intervals of actual and fitted flow were also similar (Table 2). There was some tendency for our model to underestimate pre-1990 flows at New Angeldool but this was not significant (Table 2). There were highly significant differences (p<0.001) in the modelled flow regime between pre-1990 and post-1990 development flows at all three gauges: St George, New Angeldool and Wilby Wilby (two-sided Kolmogorov-Smirnov tests p<0.0001; Table 3). Post-1990 median annual flows at St George, New Angeldool and Wilby Wilby were significantly reduced by 55%, 67% and 82% respectively compared with pre-1990 (one-sided Kolmogorov- Smirnov tests p<0.0001). These differences were reflected in 2.5% and 97.5% quantile confidence intervals (Table 3). Fig. 4. Total annual flows at Wilby Wilby, upstream of the Narran Lakes ecosystem, for pre-1990 and post-1990 development levels ( ). Pre-1990 flow model data (solid line), post-1990 flow model (dotted line). Two annual flow-breeding thresholds are shown: the higher threshold for which colonial breeding of waterbird is triggered (160,183 ML, line A) and the lowest recorded annual flow volume associated with recorded breeding (46,782 ML, line B). 84

86 Modelled pre-1990 and post-1990 development flows were then compared over the full length of record of annual flows ( ) to identify changes in frequency and intervals between years that exceeded the flow-breeding threshold for ibis breeding (Fig. 4). There were generally significant differences in annual flows under the pre and post-1990 development scenarios on a decadal time series with a significant difference over all years (t=6.409, df=18, p=<0.001) (Table 4). Under pre-1990 flow levels, there were an estimated 28 years where annual flows would have exceeded the breeding threshold, compared to only two years under post-1990 development levels (Figs. 4, 5 and Table 4). This equated to a frequency of breeding that has declined from an average of about 4 years (SE=1.22) under pre-1990 development conditions to once every 43.5 years under post-1990 development conditions. 85

87 Fig. 5. Plot illustrating the difference in total annual flow volumes and breeding responses ( ) under pre-1990 and post-1990 development levels. The filled circle represents the median, the lower and upper bounds of the box represent the 25 th and 75 th quartiles of the data respectively, while the whiskers show the extreme data point no more than 1.5 times the interquartile range from the box, unfilled circles represent outliers (R Development Core Team, 2009). 86

88 Table 2. Comparison of actual and fitted annual flow data for pre-1990 and post-1990 models of flow ( ) at three gauges from upstream to downstream (St George, New Angeldool, Wilby Wilby, see Fig. 1). Actual Flow (ML) Fitted Flow (ML) 2.5% 97.5% 2.5% 97.5% Gauge Period Median quantile quantile Median quantile quantile p-value St George Pre ,113, ,272 7,633,902 1,111, ,007 4,448, Post ,930 92,966 3,312, , ,025 1,628, New Angeldool Pre ,528 2, ,496 88,876 73, , Post , ,279 18,740 1, , Wilby Wilby Pre ,845 3, , ,657 3, , Post ,422 1, ,185 25,671 1, ,

89 Table 3. Comparison of the annual pre-1990 and post-1990 modelled flow data ( ) at three gauges from upstream to downstream (St George, New Angeldool, Wilby Wilby, see Fig. 1) of the Narran Lakes ecosystem. Pre-1990 total annual flow (ML) Post-1990 total annual flow (ML) 2.5% 97.5% 2.5% 97.5% Gauge median quantile quantile median quantile quantile p-value St George 936, ,173 3,512, , ,022 2,111,185 < New Angeldool 88,501 9, ,561 45,532 1, ,273 < Wilby Wilby 84,060 13, ,137 29, ,732 <

90 Table 4. Decadal flow volumes at Wilby Wilby under pre-1990 and post-1990 development flows, frequencies of and intervals between ibis breeding. Time period Total decadal flow Wilby Wilby (ML) Opportunities for breeding Average breeding interval (yrs) a Pre-1990 Post-1990 % decline p-value Flows >160,183 ML Flows <160,183- >46,782 ML Flows <46,782 ML Pre- Post- Pre- Post- Pre- Post- Pre- Post b 936, , n.a , , < n.a n.a ,285, , n.a ,943, , n.a ,527, , n.a ,070, , n.a ,870, , n.a ,979, , ,833, , n.a All years total ,214,018 3,627, < n.a a average interval between breeding-flows >160,183ML b not a full decade 89

91 Discussion Australia s most important site for breeding ibis is significantly threatened by upstream water resource development. We showed that opportunities for breeding on flows >160,183 ML have been reduced by 30% with the frequency of breeding changing from on average once every four years to once in 43.5 years. The magnitude of this impact is significant on a global scale with implications for the management of rivers around the world and within Australia, particularly the Murray-Darling Basin. There have been similar findings at other key breeding sites in Australia, the Macquarie Marshes, and the Lowbidgee (Murrumbidgee River) (Kingsford and Thomas 1995, Kingsford and Johnson 1998, Kingsford and Thomas 2004). Water resource development upstream of the Macquarie Marshes reduced inundated areas by 50% resulting in a decline in waterbird species diversity and abundance (Kingsford and Thomas 1995). The size of breeding colonies and frequency of breeding has also been reduced (Kingsford and Johnson 1998). The Lowbidgee wetlands have been reduced in area by 76.5% since the 1900s as a result of dams and floodplain development impacting significantly on species abundance and diversity (Kingsford and Thomas 2004). Due to Narran Lakes importance as Australia s largest ibis breeding site, regulation has the potential to impact on the viability of species to persist in Australia. Following resource development in the 1990s, we found that ibis breeding was stimulated on lower total flow volumes than observed historically (Figs. 2 & 4). Analysis of the shortterm data ( ) showed no significant effect of regulation on frequency of breeding events (p=0.9702; Table 1). In contrast, our simulation of long-term trends (using flow patterns) highlighted how regulation may result in a dramatic decline in the frequency of ibis breeding at Narran (p=<0.001) (Table 4). These results promote the utility of long-term monitoring and modelling of impacts which may not be evident in short-term records in highly variable environments. However, the shortterm analysis did identify a clear downward trend in flow sizes resulting in breeding post 1990 (Fig. 5). This suggests that while there has been a reduction in optimal large 90

92 flow events for breeding, breeding opportunities for birds still exist but on sub-optimal flows. Similarly modelled changes in frequency may be overestimated (once in 43.5 years) and ibis may breed more frequently on smaller flows, however breeding success on smaller flow volumes may be compromised. Ibis may need to reproduce on sub-optimal flows during their life-span. Such flows may not be sufficient for successful breeding (Brandis and Kingsford in press). Straw-necked ibis may live up to 29 years (ABBBS, 2009) but the average life span is more likely to be years, with adult stage reached after 3-4 years (Marchant and Higgins 1990). Historically under pre-1990 development conditions, ibis were estimated to breed at Narran Lakes 3-5 times during their life span; under simulated long term post-1990 conditions ibis may not have the opportunity to breed at Narran Lakes during their life time in optimal conditions for success. The relative importance of Narran Lakes compared to other potential breeding sites becomes increasingly questionable. As there are considerable impacts also occurring on other breeding sites in the Murray- Darling Basin (Kingsford and Johnson 1998, Kingsford and Thomas 2004), the long-term effects on species such as colonially breeding ibis could be devastating. Examination of survivorship should be a priority to determine what are the likely long-term impacts which will depend on changes to frequencies of breeding across the range of breeding sites and breeding success within individual sites. We examined threshold triggers for ibis breeding at Narran Lakes, not breeding success. Initiation of breeding may not necessarily result in breeding success. So, while flows may be of sufficient volume to initiate breeding, other hydrological and environmental factors influence breeding success. These include duration of inundation, fluctuations in water depth, availability and quality of food resources and nesting habitat, predation and weather. Fluctuations in water levels can trigger abandonment of nests and chicks by adults (Kushlan 1987, McCosker 1996, Scott 1997, Kingsford 1998, Brandis and Kingsford in press). Abandonment has been observed at 91

93 Narran Lakes following breeding initiated by both local rainfall and river flows. In January 2010 following local rainfall, an estimated 20,000 straw-necked ibis began nesting and egg laying but all were abandoned following no further rain or river flows, while in 2008 straw-necked ibis abandoned chicks at all stages of development following rapid drops in water levels in the colony site (Brandis and Kingsford in press). The management of flows once breeding has started is also crucial in ensuring the success of breeding. Australia has national and international obligations for ensuring that the ecological character of the Narran Lakes ecosystem does not change since gazettal in We have shown that the damaging effects of reduced flows are significant for this wetland and its breeding waterbirds under post-1990 development conditions. Whether water resource development continued after 1999 is not known but clearly the ecological character values for which this wetland was recognised, particularly in relation to the breeding of colonial waterbirds has changed irrevocably. Listing was primarily due to the large colony sizes observed (400,000 straw-necked ibis in 1983). These problems reflect the considerable changes in flows to the site. In the decade , the lowest total flows in nearly a century were recorded at Wilby Wilby (Table 4) but while these reflect the ongoing below average rainfall that has been experienced in the Murray Darling Basin since 2002 (BOM 2010), our analyses clearly show that flow volumes to the Narran Lakes ecosystem would be considerably higher without development on the Lower Balonne floodplain (Fig. 4; Table 3). Modelling by the CSIRO (2008b) found that average annual flows in the Narran River have been reduced by 58%. This supports our findings of mean annual flow reductions of 59% at Wilby Wilby, although we believe that the median annual reduction of 76% more accurately represents changes in flow volumes (Table 3). These problems are likely exacerbated because we did not include effects of water resources development upstream of St George in our modelling which result in diversions of flow (CSIRO 2008b). Initial water resource development began during the 1950s and 1960s when flows were altered by 92

94 small scale irrigation. In 1972, Beardmore Dam (81,700 ML) at St George was completed, supporting the St George Irrigation Scheme supplying 134 km 2 of irrigated crops (ANCOLD 2009). Current protocols for management of flows for waterbird breeding compound these problems. Current water management of the Condamine-Balonne is on a flow event basis (QLD WRP 2004). An objective of this water management is to improve water availability for breeding of colonial waterbirds in the Narran Lakes Ramsar site; primarily by reducing water harvesting (10% for a maximum of 10 days) if flows of sufficient volume are available to fill the Narran Lakes occur during April August (QLD WRP 2004). This is problematic on two counts: significant reduction of flows and the inappropriate timing for this objective. Flows that reached Narran Lakes were predominantly (74%) during the summer-autumn months (Fig. 3) and flows that most frequently resulted in ibis breeding were also during the summer months. The largest reductions in flows to the Narran Lakes ecosystem from water resource development have occurred in February (CSIRO 2008b) and no flow management rules for waterbird breeding apply. Flow management rules to reduce upstream extractions and flows to the Narran Lakes ecosystem only apply during April-August when only 20.5% of the flows that stimulated breeding occurred. There are no provisions for reductions in water harvesting during the summer months when the majority of flows and breeding events occur (Fig. 3). There is also no definition of what flow volume is sufficient to fill Narran Lakes and trigger reductions. The Water Resources Plan (2004) also allows for increased irrigation access during large, less environmentally important flow events to compensate for reductions (Independent Audit Group 2004). There is a perception that large floods are less environmentally important although no analysis exists to support this notion. We have shown that large floods are particularly important and it is likely that these provide a more abundant food supply ensuring greater breeding success, once initiated. Contrastingly, if floods are not of sufficient magnitude, there is likely to be abandonment even if a breeding event is triggered (Brandis and Kingsford in press). 93

95 The world s rivers and wetlands and their dependent organisms are in a parlous state. Much of this damage has occurred because of upstream development of water resources for irrigation. There are relatively few global examples of how much damage has occurred to populations of colonially breeding waterbirds. Contributing to the difficulty is the challenge of trying to model disturbance over long time periods for which there are relatively few data. We have shown by using data on the breeding of waterbirds and their relationship to modelled flows, there are opportunities to identify the extent of ecological damage. There are options available to redress some of the damage through improved management of environmental flows. This can be achieved by reducing impacts of diversions on colonially breeding waterbirds and other organisms by returning more water to a river and dependent ecosystem such as the Narran Lakes ecosystem. There are also considerable challenges in improving the sophistication of delivery of environmental flow water to achieve better environmental outcomes. Our study showed the magnitude of impacts water resource development has had on Australia s most important ibis breeding site. This is primarily the reason why this site is listed as a site of international importance under the Ramsar Convention and yet governments have generally done little to address the growing problem caused by diversion of water upstream. These findings show again the long-term impacts of water resource development on a well-known wetland ecosystem. Mitigation can only occur if the impacts of water resource development are reduced and through improved management of environmental flows. Acknowledgements This study was supported by the Australian Wetlands and Rivers Centre at the University of NSW. 94

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101 Chapter 4 Crisis water management and ibis breeding at Narran Lakes in arid Australia Brandis, K. and Kingsford, R.T. Environmental Management (in press) 100

102 Abstract Narran Lakes is a Ramsar site recognised for its importance for colonial waterbird breeding, which only occurs after large highly variable flooding events. In 2008, 74,095 pairs of ibis bred for the first time in seven years, establishing two contiguous colonies, a month apart. Most (97%) of the colonies consisted of the straw-necked ibis (Threskiornis spinicollis) with the remainder consisting of glossy ibis (2%, Plegadis falcinellus) and Australian white ibis (1%, T. molucca). Following cessation of river flows, water levels fell rapidly in the colony site, resulting in a crisis management decision by governments to purchase (AUS$1.87 million) and deliver water (10,423 ML) to avert mass desertion. There were significant differences in the reproductive success of each colony. Based on estimates of mortality rates for straw-necked ibis, from 33,047 eggs layed in colony 1, 19,696 chicks hatched and 18,554 chicks fledged (56% success) while in colony 2 only 6,811 chicks fledged from 98,289 eggs layed and 38,923 hatched (7% success). All reproductive success variables for the egg stage were similar between the two colonies with comparable clutch sizes and hatching rates. Divergence in mortality rates occurred at the chick stage when water depth in colony 2 was significantly lower than that experienced by colony 1 at the same stage of chick development. The location of nests and water depth were key variables in explaining chick mortality. The results of this study identify the impact of upstream water resource development on colonial waterbird breeding and have implications for water management policies. 101

103 Introduction There are 36 ibis species around the world (Family Threskiornithidae) and most breed in colonies: South Africa (Kopij 1999), Europe (Tourenq et al. 2000; Fasola et al. 2010), India (Devkar et al. 2006), Morocco (Smith et al. 2008) and the United States of America (Ivey and Severson 1984; Earnst et al. 1998; Taft et al. 2000; Kelchlin and Wright 2002). Wetland inundation is pivotal in stimulating their breeding and reproductive success, whether seasonal, managed or natural. Africa s most common and widespread species the sacred ibis (Threskiornis aethiopicus) breeds seasonally with rainfall and is well adapted to breeding on dams when water levels are high (Kopij 1999). In India, the oriental white ibis (Threskionis melanocephalus) breeds seasonally with the onset of the monsoon when flooding is widespread (Devkar et al. 2006). In South Carolina, reproductive effort of white ibis (Eudocimus albus) is influenced by variability in seasonal rainfall, with greater numbers breeding during wet years when food resources are more plentiful (Bildstein et al. 1990). In Australia, the three species of ibis, straw-necked Ibis (Threskiornis spinicollis) glossy Ibis, (Plegadis falcinellus) and Australian white ibis (T. molucca) breed in colonies following inundation of wetlands (Carrick 1962; McKilligan 1975; Kingsford and Johnson 1998; Leslie 2001; Kingsford and Auld 2005). The three ibis species reproduce throughout Australia but their breeding stronghold, in terms of frequency of breeding and size of breeding colonies, is the Murray-Darling Basin (Fig. 1, Marchant and Higgins 1990). There are 49 recorded breeding sites for the three ibis species in Australia and 23 are in the Murray-Darling Basin (Barrett et al. 2003), one of 12 river basins across Australia. Breeding colonies can number in the tens of thousands of individuals, following flooding of inland river and wetland systems (Marchant and Higgins 1990; Kingsford and Auld 2005). The more important sites include Bool Lagoon, the Lachlan wetlands, Macquarie Marshes, Narran Lakes and Lowbidgee floodplains (Marchant and Higgins 1990). Given dependence of breeding ibis on flooding and the major reductions in river flows to floodplains in the Murray- 102

104 Darling Basin (Kingsford 2000; Arthington and Pusey 2003), there may be long-term effects of declining river flows on populations of the two predominantly inland ibis species: straw-necked ibis and glossy ibis. Australian white ibis are well established in urban environments (Martin et al. 2007) and so less likely to be affected by reduced flooding of rivers with regulation (Kingsford 2000). For regulated rivers, reductions in flooding have diminished frequency and extent of ibis breeding (Leslie 2001; Kingsford and Johnson 1998) and possibly reproductive success of waterbirds (Crozier and Gawlik 2003). In particular, rapid changes in water level illicit behavioural responses such as nest construction or abandonment in ibis species of nests with eggs or chicks (Leslie 2001; McCosker 1996; Kingsford and Auld 2005). Further, release patterns for environmental flows may critically influence availability of breeding habitat for ibis (Kingsford and Auld 2005). The Narran Lakes system is one of the more significant sites for breeding ibis in Australia (Marchant and Higgins 1990). It was recognised in 1880 as an important waterbird site (Abbott 1881) and its national importance realised when an estimated 200,000 pairs of ibis bred in 1983, the largest in Australia (Marchant and Higgins 1990), although this estimate was not rigorously quantified. Tens to hundreds of thousands of ibis breed in colonies when there is sufficient flooding (Beruldsen 1985; Brooker 1993; Ley 1998a, b). In 1988, part of the Narran Lakes and surrounding terrestrial areas were protected as a Nature Reserve (20,799 ha) (Fig. 1) and then in 1999, it was recognised internationally and listed as a Ramsar wetland, primarily for its national and international significance as a major breeding site for the three ibis species (Ramsar 1999). The Narran Lakes system relies on flows from the rivers of the Condamine-Balonne catchment in the northern part of the Murray-Darling Basin (Fig. 1). The Condamine- Balonne River originates in the Southern Downs region of Queensland and flows west to south west into New South Wales. It is a single channel for most of its length until St 103

105 George where it bifurcates into a series of anastomising channels (Thoms and Parsons 2003), comprising the Narran, Birrie, Bokhara and Culgoa Rivers. Of these, only the Culgoa continues to join the Darling River. The Condamine-Balonne catchment has experienced considerable water resource development, particularly affecting flows to the Lower Balonne floodplain, including the Narran Lakes system. Water resource development on the Lower Balonne began during the 1950s and 1960s with small scale irrigation projects, continuing with flow alterations after 1972 with the Queensland Government sponsored St George Irrigation project and constructed Beardmore Dam. In the mid 1990s, there was considerable development through the capture of floodplain flows in large off-river storages (Kingsford 2000b; Thoms and Parsons 2003). Diversions from the Condamine-Balonne are stored in 208 GL of public storages and 1,582 GL of privately owned off-river storages, making it one of the more highly developed rivers in the Murray-Darling Basin (CSIRO 2008). This development has caused an estimated 58% reduction in average annual flows to the Narran Lakes system (CSIRO 2008). Historically the Lakes filled on average every two years (Ley 1998a) but recent ( ) filling events now occur about every four years. This is estimated to have decreased the frequency of colonial waterbird breeding with the number of years of suitable waterbird breeding habitat estimated to be reduced by 60% (CSIRO 2008). In 2008, ibis began breeding in the Narran Lakes system for the first time since 2001, after failing to breed during a small inundation event in During the 2008 event, governments of the Murray-Darling Basin Commission (Australian Capital Territory, New South Wales, Queensland, South Australia, Victoria and Australian Government) made the extraordinary policy decision to intervene with a purchase of 10,423 ML (AUD$1.87 million) to ensure that falling water levels would not produce a mass desertion of breeding ibis. This decision was primarily based on our provision of real time data of the risk of mass desertion and mortality. In this study, we aimed to determine the timing of breeding, size of breeding event, clutch size and reproductive 104

106 success (eggs, chicks) of the ibis colony during the 2008 breeding event, in an effort to determine the success of the water purchase intervention. Methods Study area Narran Lakes is the terminal wetland system on the Narran River which has a small, shallow main channel with contiguous floodplain (Fig. 1). It flows intermittently with heavy rainfall in the upper catchment, usually producing large floods during the summer, and occasionally spring (Bureau of Meteorology 2008). River flow data for were obtained for the Narran Park gauge (Figs. 1 and 2b) (NSW Government Water Information 2009). The region affecting flows to the Narran Lakes system is arid, receiving highly variable median annual rainfall of 431 mm (Walgett mean=466±155 S.D.; n=38 years). During the 2008 breeding event, we collected rainfall data for the upper catchment at St George and also locally at Narran Lakes (Grawin Opal Fields) (Fig. 1). Narran Lakes consists of three lakes, Back Lake, Clear Lake and Narran Lake, a large area of floodplain and the main channel of the Narran River covering 17,439 ha (Fig. 1). During floods, the Narran River fills Clear and Back Lakes and then fills Narran Lake if flows are sufficiently large. When Clear Lake fills, Narran flows then fill Back Lake and the northern floodplain (Fig. 1). Clear and Back Lakes are surrounded by extensive channelised floodplain, vegetated with lignum (Muehlenbeckia florulenta), river cooba (Acacia stenophylla), phragmites (Phragmites australis) and river red gum (Eucalyptus camaldulensis) (McGann et al. 2001). The large areas of lignum are the main area where ibis traditionally nest between Clear and Back Lakes (Ley 1998b). 105

107 Figure 1. Location of a. the Narran River (N), Narran Park flow gauge (NP), the Narran Lakes system including its floodplain (hatched), lakes (filled, CL-Clear Lake, BL-Back Lake, NL-Narran Lake) and boundary of the Nature Reserve (dashed line), within the b. Condamine-Balonne catchment (filled), showing Narran Park flow gauge to the south and rainfall station of St George to the north, within the Murray-Darling Basin (stippled) in south-eastern Australia. Breeding Straw-necked ibis, Australian white ibis and glossy ibis began nesting in mid January Straw-necked ibis made up about 97% of all birds, glossy ibis 2% and Australian white ibis 1%. Surveys of the ibis colony began on the 29 th January 2008 and continued until all chicks were fledged by 24 th April There were two clear breeding events 106

108 (colony 1 and 2), varying in start dates and location of breeding. The boundaries of the colonies were mapped (GPS, Trimble Recon with ESRI ArcPad) by tracking the edge of the colonies in a canoe on two dates 29 th January and 20 th February 2008, close to when each colony established. This provided a survey frame for random sampling of straw-necked ibis nesting sites to estimate reproductive success. A nesting site was a group of nests (3-102 nests) separated from the next nesting site by a channel of water or non flattened vegetation (Fig. 5). On the 29 th January 2008, we identified 34 nesting sites of straw-necked ibis, randomly selected around the perimeter of the colony 1 but, on the 7 th February 2008, seven of these were inundated and abandoned and so we replaced these with another 10 randomly selected nesting sites. After colony 2 began on 15 th February 2008, a further 40 nesting sites of straw-necked ibis were randomly selected from this colony along the perimeter and scattered throughout the colony (Fig. 5). In addition, 10 glossy ibis nests were randomly selected from the area where the species nested (Fig. 5). No Australian white ibis nests were surveyed due to low nest abundance and scattering throughout the colony (<50 nests). In total, we surveyed 87 nesting sites, comprising about 1000 individual nests. The locations of sample nesting sites were recorded and marked using coloured tape. To estimate reproductive success, we surveyed all sample nesting sites 29 th Jan-24 th April, every 8-10 days, during the early morning (6am-11am) or late afternoon (3pm- 8pm) to avoid heat stress on the birds (max temp C). A total of six surveys of each colony were conducted. During each survey, we counted the number of nests, eggs, and chicks, clutch size, stage of chick development, and mortality for each nesting site. From our observations we identified six stages for young based on development (1 egg stage and five chick stages): egg (1-20 days old); downy chick (recently hatched, downy feathered, days old); squirter (larger chicks with some feather development, that remained in nests, days old), runner (mixture of developed and down feathers, ability to leave the nest on foot, days old), flapper (could not fly, flapped while moving between nests, days old) and flyer, (young 107

109 juvenile that could fly, days old). Birds in the latter group were clearly distinguishable from adult birds because their plumage was grey (Marchant and Higgins 1990). Based on our observations of 87 nesting sites we identified day 22 as the point at which most eggs in a nest had either hatched or were not going to hatch. This was used to examine differences in hatching success between the two colonies. We analysed reproductive success of eggs and chicks separately for each colony of straw-necked ibis and the glossy ibis nests using the Mayfield method, accounting for bias related to staged identification of nests through incorporation of observation days into survival estimates (Mayfield 1975; Johnson and Shaffer 1990). Failure to account for the time a nest is under observation compared to the total time exposed to predation or other threatening events (e.g. severe weather) may overestimate survival (Johnson 1979; Klett and Johnson 1981). Egg stage duration was determined as the point when the ratio of chicks exceeded eggs by 2:1. For both colonies this was calculated to be an average of 17 days (±5 days). The egg stage was clearly separated but we were only able to measure chick mortality to the runner stage as chicks at or older than flapper stage were moving around the colony and no longer associated with their nests. For mortality measures chick stage refers to chick development stages downy chick to runner (days 21-35). We also censused total number of nests in the colony. Few studies adequately quantify colony sizes of breeding ibis in Australia, relying predominantly on extrapolations from a sample of data (Kingsford and Johnson 1998; Kingsford and Auld 2005) or simple estimates based on the spatial extent of the colony. We used high resolution (6 cm pixel size) photography, taken from a fixed wing aircraft ( 1,000 m above ground, 24 th February 2008). The photographs were taken following inundation of parts of colony 1 and after the establishment of colony 2. At this time, adult birds were attending either chicks (colony 1) or eggs (colony 2). Any re-nesting by colony 1 birds that lost nests would have been photographed. The photographs were orthorectified and mosaiced 108

110 to provide a spatially accurate seamless photographic layer of the colony sites. Each nest was visually identified and location recorded using GIS software (ArcGis 9.3). The photographic and nest location layers were then overlayed with the field recorded colony boundaries to verify the colony extent and boundary. Nest locations were ground-truthed by comparing GPS locations of sample nesting sites recorded on the ground and on aerial photographs; all 87 nesting sites matched. We deducted Australian white ibis nests from the overall number to focus only on straw-necked ibis nests. Glossy ibis nests were not visible in the photographs as they were located within or under the lignum bushes rather than on flattened lignum. Maximum and minimum heights above water were recorded at each nesting site (i.e. lowest and highest nest). We also measured water depth at each nesting site, during each survey, nesting site and at Back Lake gauge each day. We provided predictions based on these data to governments of likely risk of abandonment of nest sites with drying up of the wetland. Eight dead chicks were collected (24 th April) and tested for pesticides and gut content. Statistical Analysis We tested (independent samples t-test) for differences between the two colonies in relation to three nesting variables: number of nests per nesting site, mean clutch size hatching rates; and mean number of chicks per nest at day 22. For number of nests per nesting site and clutch size, analyses included data collected prior to the inundation of parts of colony 1. Hatching rate data were only available for colony 1 post inundation. Potential bias due to sampling nests around the edge was tested for by using a subset of colony 2 sites distributed throughout the colony, compared to sites located along the edge of the colony, using t-tests on clutch size, egg and chick mortality. We also tested for effect size to measure the strength of the relationship between variables (Nakagawa and Cuthill 2007). 109

111 We compared daily mortality rates between the two colonies at egg and chick stages. We also tested for the effect of water level on the reproductive success of each sampled nesting site using daily mortality rates (egg and chick stages). Three Gaussian generalised additive models (GAM) (water depth, spatial location (nest location recorded as latitude and longitude), and water depth and spatial location) were compared to determine which variables best explained egg and chick mortality. To estimate the distribution of mortality for the two colonies, we built a generalised additive model using Gaussian regression to predict whether egg and chick mortality across both colonies varied with spatial location and water depth. We further investigated this relationship by calculating a Spearman rank correlation between egg mortality and depth. We also tested if nest density was positively correlated to reproductive success, as in some colonially breeding species (Burger 1981), by using the mapped nest location data to calculate a kernel density estimate and determine variation in mortality of eggs and chicks across colonies 1 and 2 in relation to nest density. We transformed some data to improve normality and homogeneity of variance (Quinn and Keogh 2002): log (x+1) for number of nests per nesting site and square root for hatching rates; number of chicks at day 22; nest height and water depth data. Clutch size data were normal but had heterogeneous variance, so the unequal variances t-test was used (Ruxton 2006). Egg and chick mortality data were fourth root transformed to improve normality and homogeneity of variance (Quinn and Keogh 2002). T-tests were done using SPSS Statistics 17.0 and GAM development and analyses were done using R (R Development Core Team 2008). We used ArcGis 9.3 Spatial Analyst for spatial statistical analyses (ESRI 2008). 110

112 Results Breeding High upstream and local rainfall in November and December 2007 produced a flow of 48,089 ML into Narran Lakes system beginning on 23 rd December 2007, with three peaks extending until 16 th March 2008 (Fig. 2). It took about six weeks for upstream rainfall at St George to reach the Narran Lakes as flow (Fig. 2). There was also high local rainfall at Narran Lakes in December, mm (monthly total) that contributed to inundation. The flow flooded Clear Lake, Back Lake and the Long Arm but only just reached Narran Lake (Fig. 1). The first flow peak to reach the Narran Lakes system was on the 30 th December 2007 (2,661 ML day -1 ) and then there was a smaller flow peak (2,041 ML day -1 ), a month later on the 7 th February 2008, following further upper catchment rainfall (Fig. 2). The third and final peak on the 29 th February was considerably smaller (999 ML day -1 ) than the previous two (~50% less) and, by 16 th March flows into Narran Lakes system had ceased (Fig. 2). A total of 48,089 ML reached the Narran Lakes system by this stage. On the 22 nd March, 10,423 ML of water was purchased from the irrigation industry upstream and reached Narran Park on the 2 nd April with a peak flow of 206 ML day -1 on the 20 th April (Fig. 2). This flow maintained water depths at 22.5 cm from the 4 th 15 th April, by the 20 th May water had receded from the Back Lake gauge. The initial flow event lasted 97 days but was extended to 152 days with the purchased water (Fig. 2). Straw-necked ibis colony 1 (44.47 ha) established on 15 th January 2008, 16 days after the initial peak flow reached Narran Park gauge (Fig. 2). Nests were built on lignum (a shrub 2-3 m in height) and phragmites (a perennial grass 2-4 m in height) between Clear and Back Lakes (Fig. 3). The second flow peak inundated 7 (322 nests) of the low lying survey nesting sites in colony 1 (Fig. 2). Between the 9 th and 19 th February 2008, colony 2 ( ha) established adjacent to colony 1 (Fig. 3). In total, there were 71,872 straw-necked ibis nests on the 24 th February (post-inundation of colony 1): 111

113 22,280 were in colony 1 (31% of nests) and 49,592 were in colony 2 (69%). Nest density was higher in colony 1 with about 501 nests ha -1 compared with 342 nests ha -1 in colony 2. On the 20 th March, the water depth was 40 cm at the Back Lake gauge but we predicted that given the trajectory of decline water depths would drop to 28 cm by 1 st April (actual water depth fell below 28 cm on 29 th March), the level when nesting established (Fig. 2). With knowledge of the propensity of ibis to abandon breeding with falling water levels, we advised relevant governments of a potential catastrophic abandonment. Using the trajectory in water depth decline, we predicted that desertion could occur of the entire colony 2, with successful chicks fledging only from colony 1. Governments then purchased an additional 10,423 ML water to prolong inundation until chicks in colony 2 fledged (Fig. 2), a flow that reached the colony site on the 2 nd April and maintained water levels at 22.5cm until the 15 th April when levels began to fall again until the 10 th May when water levels fell below 10cm (Fig. 2). By the 1 st April few adult ibis were observed in the colony site. 112

114 Figure 2. a. Total daily rainfall at St George and b. Total daily flow at Narran Park (Nov May 2008, solid line), flow from purchased water (dotted line) and water depth (dashed line) in Back Lake in relation to the beginning and end of breeding by straw-necked ibis nesting in colonies 1 and 2. The filled circle signifies when water was purchased (22 nd March). 113

115 Reproductive success Based on estimates of mortality rates for straw-necked ibis, from 33,047 eggs layed in colony 1, 19,696 chicks hatched and 18,554 chicks fledged (56% success) while in colony 2 only 6,811 chicks fledged from 98,289 eggs layed and 38,923 hatched (7% success). There were significantly more nests per nesting site in colony 1 prior to inundation (10 th February) than in colony 2 (t=-3.098, df=60, p=0.003) but no differences in number of nests per nesting site between colony 1, post inundation, and colony 2 (t=1.180, df=57, p=0.243, Table 1). Similarly, there was no significant difference in clutch size between colony 1 pre-inundation (t=0.177 df=57, p=0.860) and post inundation (t=-0.403, df=44.76, p=0.689) compared to colony 2 (Table 1). There was also no significant difference in hatching rate (the number of eggs hatched to produce chicks) between colony 1 (post inundation) and colony 2 (t=1.559, df=63, p=0.124) (Table 1). There were no significant differences between the average number of chicks per nest at day 22 between colonies 1 and 2 (t=1.508, df=51.7, p=0.138) with a medium effect size (d=0.528) (Table 1). There were no significant differences between nests on the edge and within colony 2: clutch size (t=0.397, df = 40, p=0.693) and egg (t=-1.324, df=11.191, p=0.212) or chick mortality (t=-0.138, df=33, p=0.891). Daily mortality rates for eggs in colony 1 (postinundation) were significantly lower than colony 2 (Table 1; t=-3.237, df=52.553, p=0.002), with a medium effect size (d=0.535). Daily mortality rates for glossy ibis at egg stage were also lower than respective straw-necked ibis but, at chick stage, were higher than straw-necked ibis in colony 1, but lower than colony 2 (Table 1). The mortality of chicks in colony 2 was significantly higher than in colony 1, (t=-6.895, df=68, p<0.001), with a large effect size (d=1.692). Chicks at all stages of development were found dead on nests in colony 2. There was limited predation on chick carcasses and no pesticides found in the eight chicks analysed. Gut contents large enough for There were no significant differences between nests on the edge and within colony 2: clutch size (t=0.397, df = 40, p=0.693) and egg (t=-1.324, df=11.191, p=0.212) or chick mortality (t=-0.138, df=33, p=0.891). Daily mortality rates for eggs in colony 1 (post- 114

116 Figure 3. Location of colony 1 (open area, ha) and colony 2 (filled area ha) on the floodplain (stippled) of the Narran Lakes system in relation to Back Lake and Clear Lake (see Fig. 1). inundation) were significantly lower than colony 2 (Table 1; t=-3.237, df=52.553, p=0.002), with a medium effect size (d=0.535). Daily mortality rates for glossy ibis at egg stage were also lower than respective straw-necked ibis but, at chick stage, were analyses showed small traces of seed material and chicks had little muscle on their keel-bones. 115

117 Maximum and minimum heights of nests above water at nesting sites were significantly higher in colony 1 compared to colony 2 for all stages of chick development (Table 2). These differences reflected similar trends in water depth at nesting sites with significant differences in water depth between the colonies at each stage of chick development (Table 2). Water depth was higher at all stages of chick development in colony 1, except at the egg stage when water was higher for colony 2 (Table 2). Glossy ibis nests were only within colony 1 and experienced the same variations in water levels as the straw-necked ibis nests in this colony (Table 1). 116

118 Table 1. Mean (±SE) measures of reproductive success in colonies 1 and 2 of Strawnecked Ibis and Glossy Ibis nesting in the Narran Lakes system in the 2008 breeding event. Mortality rates were calculated using the Mayfield method (Mayfield 1975). Variable Colony 1 Colony 2 Glossy Ibis Nests per nesting site 16 (3.3) 12 (2.6) 1.4 (0.22) 6.8 (1.8) a Clutch size 1.88 (0.14) 1.95 (0.07) 1.98 (0.32) 1.93 (0.09) a Hatching rate (eggs-chicks) 0.62 (0.06) 0.47 (0.05) 0.82 (0.66) No. chicks per nest (day 22) 0.92 (0.14) 0.60 (0.08) 1.36 (0.34) Daily mortality rate during egg stage Daily mortality rate during chick stage 0.04 (0.005) a 0.06 (0.01) 0.03 (0.02) 0.004(0.004) 0.05 (0.1) 0.02 (0.1) Probability of surviving egg stage b Probability of surviving chick stage c Probability of surviving from egg to flapper stage a Post inundation Colony 1 (10 th February) b 17 days straw-necked ibis; 14 days glossy Ibis c 15 days straw-necked ibis; 15 days glossy ibis 117

119 Table 2. Mean (±SE) maximum and minimum heights (cm) of nests above the water, water depth at each nesting site (cm) and results of t-tests at comparable stages of chick development (days in parentheses) for colonies 1 and 2. Chick development Variable Colony 1 Colony 2 t df p Egg (1-20) Nest height max (2.63) (2.09) <0.001 Nest height min (1.55) 15.4 (1.21) <0.001 Water depth (1.88) (2.32) <0.001 Downy chick (21-25) Nest height max (1.16) (1.5) <0.001 Nest height min (1.02) (0.77) <0.001 Water depth (2.14) (1.99) <0.001 Squirter (26-30) Nest height max (1.28) (2.04) <0.001 Nest height min (1.54) (1.11) <0.001 Water depth (1.26) (2.08) <0.001 Runner (31-35) Nest height max (1.30) (2.40) <0.001 Nest height min (1.32) (1.81) <0.001 Water depth (1.68) (2.20) <0.001 Flapper/Flyer a (36-45) Water depth (1.98) (4.29) a nests no longer used from this stage of chick development nest heights not recorded. 118

120 The best model for egg mortality contained spatial location only, while the best model for chick mortality contained water depth and spatial location (Table 3). Spatial location was a significant explanatory variable, accounting for 84% of the variability in egg mortality and 74% of the variation in chick mortality (Table 3). Significantly, water depth explained much of the variation in chick mortality (Table 3; Fig. 4). Models developed containing water depth and spatial location variables explained 78% of the variation in chick mortality. Water depth alone explained 50% of the variation in this model. Table 3. Effects of spatial position and water depth on egg and chick mortality using Gaussian generalised additive models (GAM). Reproductive stage Model AIC % Deviance explained P- value Egg Water depth Water depth and spatial location <0.001 Spatial location <0.001 Chick Spatial location <0.001 Water depth Water depth and spatial location We used our Gaussian models to predict daily egg and chick mortality across the colonies for all nests (74,095) based on location (Fig. 5). There was a low association between spatial location of egg and chick mortality (rho = 0.115). The variable density 119

121 of nests across both colonies did not contribute significantly to egg (p=0.453) or chick mortality (p=0.213). Figure 4. Relationship between daily chick mortality at day 22 when most chicks were hatched and water depth, resulting from a Gaussian GAM model. Discussion The Narran Lakes system is clearly one of the more important sites for breeding ibis in Australia, evidenced by the establishment of one of the larger colonies ever established on the continent of 71,872 straw-necked ibis nests. Few other sites in Australia have reached this number of breeding pairs or nests. Other large colonies of straw-necked ibis nests include; 150,000 at Bool Lagoon in 1963 (Waterman 1971), 120

122 102,000 at Narran Lakes in 1996 (Ley 1998a), 80,000 at the Lachlan Wetlands in 1984 (Magrath et al. 1991), and 60,000 in the Macquarie Marshes 1998 (Kingsford and Auld 2003).What makes this event particularly important is that the system is highly compromised by the diversion of water upstream for irrigation and the 2008 breeding event was the first time ibis had bred at Narran Lakes since Figure 5. Location of a. Straw-necked ibis sample nesting sites ( ) in colonies 1 and 2 and Glossy ibis sample nests ( ), and daily mortality density maps at egg stage (b) and chick stage (c). Unfortunately, the 2008 breeding event was a qualified success with 25,365 chicks estimated to have fledged from 58,619 eggs that hatched ( 43%). This was predominantly because of high chick mortality in colony 2 compared to colony 1, 18% of chicks fledged from hatched eggs in colony 2 compared to 94% in colony 1. Even this estimate of mortality is likely to underestimate true fledging mortality because we were only able to measure reproductive success while the chicks remained stationary, up until flapper stage (36 days old). The fledging success in colony 1 was comparable 121

123 to success rates observed in the Macquarie Marshes in 1999 (96%) and 2000 (72%, Kingsford and Auld 2003). The high mortality in colony 2 was due to insufficient flows to sustain water depth and inundation in the colony site during chick rearing (Fig. 2). Even an historic attempt at crisis water management was not sufficient to avert the high mortality, although this probably averted complete desertion of the colony. Desertion of chicks by adults is widespread in ibis species when there is sufficient flow to stimulate breeding but subsequent falling water levels cause desertion (McCosker 1996; Leslie 2001). By the 1 st April water depth at the Back Lake gauge had dropped by 44 cm from 68 cm when colony 2 established (Fig. 2). There was good evidence that the significant mortality of chicks and low fledging success in colony 2 (Table 1) was due to desertion by adults caused by falling water levels. Most reproductive success variables for the egg stage were similar between the two colonies, with divergence primarily in mortality at the chick stage. The two colonies had similar clutch sizes and hatching rates (Table 1). Straw-necked ibis clutch sizes in both colonies were also comparable to results from other studies where desertion and high mortality were not reported (Lowe 1983; Kingsford and Auld 2003). Glossy ibis clutch sizes were lower than those reported in Australian (Lowe 1983) and international studies (Boucheker et al. 2009). While daily egg mortality rates were higher in colony 2 than colony 1, eggs that survived had similar hatching rates. Also, daily chick mortality was more than ten times higher for colony 2 than colony 1 (Table 1). At day 22 of rearing, there was no difference in mortality with most chick deaths occurring after this in colony 2. Mortality rates at egg stage for both colonies were lower than rates observed in the Macquarie Marshes during ibis breeding in 1999 and 2000 (Kingsford and Auld 2003). Similarly, mortality rates for chicks in colony 1 were comparable to those observed in the Macquarie Marshes in 2000 but mortality of chicks in colony 2 was five times higher (Kingsford and Auld 2003). Further, spatial modelling showed that water depth was the best predictor of chick mortality but not egg mortality (Fig. 4; Table 3). While water depth was shown to be the best predictor it may be the rate of falls in water 122

124 levels that is the critical mechanism for determining if birds abandon nests (Kushlan 1986a, b, 1987). Finally, there were few adults observed by 1 st April with ibis present comprising chicks or flying juveniles, further indicating desertion by parental birds. Also, all eggs had hatched and chicks found dead on nests were at all stages of development in colony 2. There was no similar pattern of mortality in colony 1 at the same stages. In addition, gut contents analysis of the sample of dead chicks ruled out any potential pesticide cause and implicated starvation as chicks had few food items and little muscle on their keel-bones. Late-nesting breeders can have naturally lower reproductive success (Burger 1981) but it is unlikely that this would have accounted for the widespread and high mortality in colony 2 or the size of the difference. The purchase of additional flows (Fig. 2) probably offset complete abandonment and mortality in colony 2 (Table 2). Advice for the purchased water was an attempt to avoid water levels declining below 28 cm, the level at which breeding started in colony 1 although water depth fell below 28 cm on 29 th March (Fig. 2). Water depth was maintained at 22.5 cm from the 4 th 15 th April. The threshold for abandonment is unknown but is triggered by changes in water depth (Leslie 2001). Colony 2 experienced a fall in water depth of more than 30 cm over 40 days, coinciding with chick development (Fig. 2). Similarly in the Barmah-Millewa, breeding success declined when there was a fall by 30 cm in water levels at nesting site or within foraging areas (Leslie 2001). In colony 1, water depths were stable during most chick stages (Fig. 2). Water depth was a key variable in chick survival (Fig. 4); this may be a determining factor or a surrogate cue for other factors impacting on reproductive success such as wetland area which determines the availability of food resources. Falling water levels are probably the proximate stimulus for desertion but the ultimate factor is probably lack of food resources that decline as floods decrease. This was indicated by the poor condition of many dead chicks. Location of nests within the colony was a key variable 123

125 in egg and chick mortality although association between egg and chick mortality was low, suggesting that factors influencing egg and chick mortality may be different. Mortality at egg stage probably resulted from eggs displaced from nests: accidently by adults, removed by aerial predators or that had fallen into the water. The importance of location within the colony may be related to factors including nesting habitat quality, distance from edge, or proximity to food resources. Inundation patterns and changes in water depth were primarily dependent on flow (Fig. 2). Before river regulation ( ), a point 178 km upstream on the Narran River (Angledool) received an average of 12.5% of flow volume measured at St George (DIPNR 2004). In the flow event, Angledool received less than half of the flow at St George (5.7%). Without diversion upstream, Narran Lakes would have probably received about 84,250 ML during the flow event (based on flow relationship between Narran Park and Angeldool during event adj. R 2 =0.873). This would have probably ensured that water levels remained high throughout the breeding period, ensuring significantly higher reproductive success. Management of flows to Narran Lakes clearly has significant conservation consequences for waterbird breeding. The system is a wetland listed under the Ramsar Convention with an obligation to maintain its ecological character (Ramsar 1999). The mixed success of the 2008 ibis breeding event at Narran Lakes demonstrated that considerable challenges exist to sustainable management of breeding events, despite the efforts of governments. The impacts of diversions upstream for irrigation mean there is less water available to ensure success of breeding events. Even when governments purchased water, it did not completely prevent chick mortality. Such crisis water management is not tenable in the long term for one of Australia s most important waterbird breeding sites. A government assessment of the environmental flow release concluded that the water purchase was a success because water depth had been maintained at 30cm for the nesting area for 30 days (Cummins and Duggan 124

126 2009). Our original estimates of the success of the breeding event were qualified (Kingsford et al. 2008) and detailed analysis has now shown that there was considerably more mortality of ibis chicks than originally assessed. There is a need for better predictive models that allow assessment of the potential quantity and timing of water required to ensure a sustainable breeding event without short term needs to purchase water. In addition, detailed monitoring of breeding events is essential to ensure there is learning about the management options and their success or otherwise. Possibly an event of sufficient magnitude for breeding should be allowed to flow without diversion upstream until it reaches a threshold where extraction will not jeopardise successful breeding. Or potentially, water stored upstream is released more quickly so that water levels do not drop precipitously. Increasingly, flows are managed to ensure that ibis breeding can progress through to completion. For example, flows into the Gwydir wetlands in 1996 and 1998 were managed to maintain water depths at colony sites (McCosker 1996, 1999). During these events water was sourced from environmental water allocations managed by the state water agency. Both breeding events were deemed successful following close monitoring of water depths and the timely provision of sufficient water. Environmental flow management is well accepted in theory (Poff et al. 2003; Tharme 2003; Poff and Zimmerman 2009) and increasingly implemented in practice in Australia, South Africa, North America and the European Union (Arthington et al. 2003; Hirji and Davies 2009). Environmental flow management in the Condamine-Balonne which determines flows to the Narran Lakes system and ultimately for waterbird breeding is essentially a default process: after extraction, the remaining flows are deemed environmental. There are rules designed to allow flows of a certain magnitude through the system but loss of access to irrigation can be made up during high flows (Queensland Department of Natural Resources 2004). Access to water is determined by flow thresholds but currently these thresholds do not adequately meet the environmental requirements of 125

127 the Narran Lakes system and its breeding waterbirds. There is no environmental allocation which restricts options for active management when water is required for the environment, as during the 2008 breeding event. There were insufficient flows available for this breeding event to be completely successful because of upstream extraction of water. The rules for environmental flows in the draft Condamine-Balonne resource operations plan (Department of Natural Resources and Water 2007), precluded management of environmental flows for the 2008 breeding event. Under the rules, breeding has to occur between April and August for extraction to be reduced by 10% off peak flows for a maximum of 10 days (Department of Natural Resources and Water 2007). This flow window coincides with periods when irrigation demands for water are not high but is also outside the period when most breeding events, such as the 2009 event occur. It also remains problematic whether a 10% reduction in access to flows would be sufficient, particularly if access to compensatory flows may be available later during a flow event, reducing the flooding to the Narran Lakes system. There is a clear clash between irrigation demands and the necessary requirements for successful bird breeding in Narran Lakes. The detrimental effects of reduced availability of water, flow magnitude and duration, and seasonality of flows on breeding of colonial waterbirds are widespread in the Murray-Darling Basin (Kingsford and Thomas 1995; Kingsford and Porter 2009). The implications may be significant at a continental scale and for species such as strawnecked ibis, given the importance of the Murray-Darling Basin for breeding of colonial waterbirds. As well, vegetation structure is essential for breeding waterbirds and floodplain dependent vegetation is also significantly affected by reductions in flows (Bren 1988; Brock et al. 2006; Capon 2005). The responsiveness of colonial breeding ibis to flows and flooding allows for clear responsibilities and options for management of flows to ensure successful breeding (Kingsford and Johnson 1998; Leslie 2001; Roshier at al. 2002; Kingsford and Thomas 126

128 1995; Kingsford et al. 2004). They establish in traditional breeding sites when there is sufficient flooding to provide nesting habitat, food resources and foraging areas (Kopij et al. 1996; Trocki and Paton 2006) but these need to be sustained (Kingsford and Auld 2005). This highlights the need for Australian wetlands to be managed with adaptive environmental flow policies in recognition of the variability of the wetland systems and the requirements of waterbirds for successful reproduction. To do otherwise will continue to restrict breeding opportunities for waterbird populations at a continental scale, potentially affecting long term species survival. Acknowledgements This study was partly funded by the Murray-Darling Basin Authority and NSW Department of Environment, Climate Change and Water and supported by the Australian Wetlands and Rivers Centre at the University of NSW. This project could not have been done without the help of key individuals of the Parks and Wildlife Group of the NSW Department of Environment, Climate Change and Water: Michael Mulholland, Rob Smith, Duncan Vennell and Peter Terrill. Field work was conducted in accordance with Scientific Licence no. S The views presented in this paper represent those of the authors and not necessarily those of the funding bodies. 127

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135 Chapter 5 Management of environmental flows for colonial waterbird breeding in Australia Brandis, K. and Kingsford, R.T. 134

136 Abstract Water resource development on Australian rivers has altered natural flow regimes, significantly reducing flooding to wetlands, altering their ecology and reducing distribution and abundance of many wetland dependent species. Reductions in river flows through water resource development have already reduced breeding frequency by colonial waterbirds, potentially affecting viability of species and populations. Rehabilitation efforts involve the delivery of environmental flows and a key indicator for management is breeding success of colonial waterbirds. Colonial waterbird breeding is highly dependent on significant river flows and flooding, with aspects of volume, timing and duration critical for successful breeding. Breeding does not usually occur unless a threshold flow and subsequent flooding is reached. Successful breeding of colonial waterbirds can be improved through active management of environmental flows. This paper reviews the breeding requirements of colonial waterbirds with regards to hydrological characteristics. Environmental flows that mimic natural hydrological conditions were more likely to achieve targeted outcomes. The timing of flows releases during the warmer months, provision of flows of sufficient duration and volumes to trigger and sustain breeding are critical for successful breeding. Habitat requirements also key in breeding success are provision of nesting sites and adequate food resources. 135

137 Introduction Environmental flows describe the share of a river s water set aside for the environment, usually after river regulation and extraction for industry, agriculture and domestic use (Poff et al. 2003; Hirji and Davis 2009). Identification and importance of management of environmental flows has arisen with global degradation of riverine and wetland ecosystems, affecting structure and function (Richter et al. 2003; Poff and Zimmerman 2010). Dams, diversions and river regulation have significantly reduced flooding to wetlands, altering their ecology and reducing distribution and abundance of wetland dependent species (Kingsford et al. 2006; Poff and Zimmerman 2010). Water resource development alters magnitudes, frequencies, durations, and timing of flows (Maheshwari et al. 1995; Ren et al. 2009; Poff and Zimmerman 2010) but this impact occurs differently across responses of organisms (Walker 1985; Poff and Zimmerman 2010). Changes in flow magnitude and variability can reduce recruitment of flood dependent riparian and floodplain vegetation (Dieller et al. 2001; Johansson and Nilsson 2002; Mallik and Richardson 2009) with reduced flooding causing macroinvertebrate taxa abundance to decline (Castella et al. 1995; Jenkins and Boulton 2007). Altered flooding frequencies and magnitudes also decrease opportunities for colonial waterbird breeding (Kingsford and Johnson 1998; Taft et al. 2000), affecting reproductive success (Frederick et al. 2009; Brandis and Kingsford in press). Recognition of such effects on riparian communities has increased the focus on management of environmental flows to mitigate impacts (Arthington et al. 2010) with active management often a necessity because environmental flows are held within storages requiring release rules (Harman and Stewardson 2005; Arthington et al. 2006). Sometimes, environmental flow management focuses on the requirements of different organisms and concomitant replacement of parts of the flow regime for improvement in the condition of these organisms (Bunn and Arthington 2002; Nilsson and Svedmark 2002; Kingsford et al. 2010). Colonially breeding waterbirds are one 136

138 group for which there is a management focus because of public and government attention on their conservation and recognition of their responsiveness to river flows. Colonial waterbirds usually breed with large river flows and extensive flooding (Kingsford and Thomas 1995; Stevens et al. 1997; Kingsford and Johnson 1998; Kingsford et al. 2004). This response occurs with natural flooding but also through active management of flows (Taft et al. 2002). Such responsiveness makes colonial waterbirds useful for measuring the effectiveness of environmental flow management. Colonial breeding allows exploitation of limited but abundant resources and reduces predation risk (Burger 1981) but requires often specific habitat requirements (e.g. nesting habitat). Colonial waterbirds are a cosmopolitan group making them suitable for environmental flow management on the world s rivers and wetlands (Frederick et al. 2009; Poff and Zimmerman 2010). They commonly breed in large aggregations, feeding or nesting in wetlands (Maeher and Rodgers 1985). While species composition varies globally, they usually comprise species from the orders Pelecaniformes (cormorants and pelicans) and Ciconiiformes (wading birds, egrets, herons, ibis, spoonbills), both of which occur in Australia (Table 1). Many have common morphological and behavioural requirements, often occupying similar habitats on different continents. Most are obligate breeders in colonies but occasionally breed singly (Table 1). Single or mixed species colonies, ranging from tens to hundreds of thousands of individuals, form when there is suitable flooded wetland habitat (Kopij 1999; Ivey and Severson 1984; Earnst et al. 1998; Taft et al. 2000). Flow and flooding regimes of rivers and their dependent wetlands are highly dependent on climate which varies considerably across the Australian continent. Natural flow regimes in Australia s rivers are influenced by topography, climate, geographic location and vegetation (Kennard et al. 2010), with dryland rivers exhibiting some of the more variable flooding and river flow regimes in the world (McMahon et al. 1992; Puckridge et al. 1998; Peel et al. 2001). Large rainfall events drive river flows 137

139 with subsequent flooding providing habitat for breeding waterbirds (Roshier et al. 2001; Kingsford et al. 2004). Hydrological components of the flow regime (timing, frequency, duration, volume) dictate the timing and success of breeding by colonial waterbirds (Leslie 2001; Kingsford and Auld 2005; Chowdhury and Driver 2007). Breeding by colonially waterbirds is spatially and temporally highly variable (Boulinier and Lemel, 1986) reflecting the variability of river flows and flooding (Earnst et al. 1998; Roshier et al. 2001; Kingsford et al. in press). This abiotic variability has implications for habitat management and conservation of waterbirds (Earnst et al. 1998; Roshier et al. 2002), particularly given the significant impacts of water resource development on flow regimes (Kingsford 2000; Arthington and Pusey 2003). Water resource development has considerably reduced temporal variability by reducing the frequency and volume of flows on regulated rivers (Maheshwari et al.1995; Nilsson et al. 2005; Ren et al. 2009). Such effects are most prevalent in Australia s Murray-Darling Basin which has more water diversions and dams than other river basin (Fig. 1) (Kingsford 2000), with a 71% reduction in median annual flows at the end of Murray- Darling Basin, the Murray mouth (CSIRO 2008). The Murray-Darling Basin is also the most important region for breeding by colonial waterbirds in Australia (Marchant and Higgins 1990; Barrett et al. 2003) (Fig. 1). River regulation has reduced flooding of many of the rivers of this basin and their dependent wetlands, affecting colonial waterbird breeding (Kingsford and Thomas 1995; Kingsford and Johnson 1998; Leslie 2001; Driver et al. 2004; Kingsford et al. 2004; Kingsford and Thomas 2004; CSIRO 2008). This degradation has prompted significant investment by governments in rehabilitation of the rivers of the Murray-Darling Basin with environmental flows. In 2008, the Australian Government invested $Aus 8.9 billion in the Water for the Future Program with $3.1 billion dedicated to increasing environmental flows in rivers through the buying back of irrigation entitlements. The remaining funding was to 138

140 Fig. 1. Breeding sites for nine species of colonially breeding waterbirds ( ): Australian pelican (Pelecanus conspicillatus), great cormorant (Phalacrocorax carbo), pied cormorant (P. varius), white-necked heron (Ardea pacifica), intermediate egret (Ardea intermedia), little egret (E. garzetta), straw-necked ibis (Threskiornis spinicollis), glossy ibis (Plegadis falcinellus), and royal spoonbill (Platalea regia), within 12 continental drainage basins: I) North East Coast; II) South East Coast; III) Tasmania; IV) Murray- Darling Basin; V) South Australian Gulf; VI) South West Coast; VII) Indian Ocean; VIII) Timor Sea; IX) Gulf of Carpentaria; X) Lake Eyre Basin; XI) Bulloo-Bancannia and; XII) Western Plateau. Shading indicates the capacity of dams in each drainage basin (Geoscience Australia Dams and Water Storages 1990). increase the efficiency of irrigation infrastructure to save water, some of which was to be returned to rivers as environmental flows. As a result, there is increasing demand to demonstrate that such increases in environmental flows deliver environmental 139