ABSTRACT. Using museum collections and community surveys to monitor change in the birds of Sydney. Richard E. Major. Introduction.

Transcription

1 Using museum collections and community surveys to monitor change in the birds of Sydney Richard E. Major Australian Museum, 6 College Street, Sydney NSW 2010 ABSTRACT To identify changes in the dominance of broad groupings of bird species associated with the urbanisation of Sydney, records from the Australian Museum Ornithology Collection database and the Birds Australia Atlas Database were analysed. This historical comparison suggests that parrots, large honeyeaters, large carnivores and exotics are the species that have historically been the most tolerant of urbanisation. The Birds in Backyards project is a research, education and conservation program directed towards the birds that live where people live. Part of the project involves the facilitation of backyard bird surveys conducted by volunteers who enter their survey data on line. This steadily growing database can be used to examine the relationships between common urban birds, both amongst each other and with human-generated habitat variables. It can also be used to identify local variation in bird communities and has potential for monitoring temporal change. Examples of these uses include analysis of 1) the Superb Fairy-wren and Noisy Miner, whose local distributions are negatively correlated; 2) the Superb Fairy-wren and Australian King Parrot, which show opposite patterns of distribution north and south of Sydney Harbour; and 3) the Channel-billed Cuckoo which appears to have been much more common in Sydney in 2007 than in The Birds in Backyards Guidelines for Urban Bird Habitat and the backyard bird surveys are increasingly being used by local councils in Sydney as tools to assist initiatives to maintain urban biodiversity. Key words: urban birds, collection, birds in backyards, chat, fairy-wren, miner, parrot Introduction Sydney has the longest history of human impact of any location in Australia and there have been some very conspicuous changes to the composition of its bird community both in historical and recent times (Recher 1972; Hoskin et al. 1991). These changes have been detected from investigation of collections, diaries, field note-books and databases. Given that Sydney is now highly urbanised, increasing urbanisation is likely to have been the main driver of change in bird communities and there is some evidence that the overall bird community of Sydney continues to change in response to ongoing change in the characteristics of the contemporary urban environment. This paper examines some of the historical changes in the birds of Sydney and introduces the Birds in Backyards program which aims to monitor change in bird communities, exploring the relationships between local bird communities and the particular habitat characteristics of local areas. Assessing changes Museum collections have the potential to provide a historical perspective on the composition of bird communities, and perhaps the most likely region to find a good historical record is in the vicinity of the oldest and largest Museum in the country. The Australian Museum s bird collection contains 389 records of 88 species of land birds with date and locality information, collected within 10 km of Sydney s GPO prior to 1900 (referred to as 1900, hereafter). These records provide an indication of the birds that were common in the Sydney region prior to urbanisation. By limiting the geographical area to a 10 km radius of the GPO (Figure 1), present day nonurban habitats are excluded, allowing a comparison of pre- and post-urbanisation. Although museum collections are not random samples, it might be expected that early collectors Figure 1. Locations of records within 10 km of the Sydney GPO compiled from the Australian Museum Ornithology Collection Database prior to 1900 (blue) and the New Atlas of Australian Birds Database (yellow) between 1996 and Pp in The Natural History of Sydney, edited by Daniel Lunney, Pat Hutchings and Dieter Hochuli. Royal Zoological Society of NSW, Mosman, NSW, Australia. 2010

2 Monitoring change in the birds of Sydney would have collected, or at least not rejected, any species they encountered that were not already represented in their collection. However, it might also be expected that species, conspicuous due to their size or colour, would be over-represented, compared with more cryptic species. Interpretation of changes in bird communities based on museum records must be made with due consideration of the motivation of early collectors. More objective data on the bird community of Sydney is available for the current period. Birds Australia s New Atlas of Australian Birds provides point survey data on entire bird communities and is not subject to the constraints imposed by collection (Barrett et al. 2003). A sample of Atlas data containing 2843 records of land birds within 10 km of Sydney was analysed for the years 1998 to 2000 (referred to as 2000, hereafter). These records provide a good representation of the bird community of Sydney post-urbanisation and contain records of 98 species of land bird. Due to the non-random nature of museum collections, it is not appropriate to analyse abundance data between the museum collection and the Atlas survey. It is likely that collectors would select species of birds that were poorly represented in their collections rather than continue to collect large numbers of a species that was particularly well represented in their collections. It is still instructive, however, to compare the species that were present and absent prior and post urbanisation. What did we find? Species that were present in the early Museum data are the easiest to interpret and there are some striking changes between 1900 and Of the 88 species present in the Museum collection, 42 species were common to the Atlas sample, which consisted of 98 species. Among the losses is the Australian Bustard collected pre-1900 in Kensington, but not recorded in Another species no longer present is the White-fronted Chat, once found in six distinct localities across inner Sydney including the suburb of Chatswood. Only two populations of White-fronted Chats remain in the Sydney region, one in Newington Nature Reserve at Homebush Bay, and one at Towra Point Nature Reserve at Botany Bay. However, both these locations (in which Chats are also represented in the Museum collection) lie further than 10 km from the GPO. Small birds, particularly those favouring woodland that grows on more fertile soils have also faired poorly with increasing urbanisation. The Hooded Robin, Brown Treecreeper, and Regent are each represented in several inner-sydney locations in the Museum collection but were not recorded in the Atlas survey and now feature on the State s threatened species lists. Another two species from the 1900 sample that were absent from the 2000 sample and are now listed as threatened, are the Turquoise and Ground Parrots. Intriguingly, these species are the only parrot species for which date and locality information were recorded within 10 km of the GPO prior to In contrast, 10 species of parrot, not including the now-absent Turquoise and Ground Parrots, were recorded within this area in This is a good introduction to the group of birds that were absent from the Museum collection but were present in the Atlas data. The interpretation of these species requires a cautious approach. Historic bias Were the 10 species of parrots present today really absent (or too rare to have been sampled) in the Sydney of the late 1800 s? Or is this simply an artefact of the vagaries of early museum collecting? The answer is probably a bit of both, depending on the species. Being large and brightly-coloured we might expect parrots to be well-represented in collections compared with smaller insectivores. However, this does not mean they are immune to random collecting biases, and there is some indication of this in the historical record. For example, the Rainbow Lorikeet was encountered on the Cook (1770) expedition and was considered common in the early years of settlement (North 1912), although its numbers declined dramatically in the first half of the 1800 s (Waterhouse 1997) probably as a result of clearing for agriculture. George Caley s diary (c. 1800) provides evidence that several species of parrot were common in the Colony of NSW although the location details are not always specified and, those that are, tend to be beyond the 10 km radius. For example, the Rosehill Parrot (also known as the Eastern Rosella sensu Rosehilla) was frequently seen in small flocks and was considered, along with the King Parrot, to be the most valuable for selling to ships to take to England (Currey 1966). It was also considered to be very good eating. It is possible that these species had been hunted or had their habitat modified to the extent that they were rare and thus their collection was unlikely between 1860 and 1900, although it is also possible that their absence was a collecting anomaly. Specimens from that time may have been exchanged, or perhaps they were collected without the locality and/or collection date required for inclusion in this analysis. In contrast, Sulphur-crested Cockatoos, though recorded on the periphery of Sydney in early days (Currey 1966), were not known from central Sydney, and their prominence in the Atlas data appears to reflect a genuine benefit from urbanisation. Given that there will always be uncertainty when inferring the absence of species from Museum data, it is more appropriate to consider trends across groupings of species rather than place too much reliance on individual species. Taking this approach, it would seem that parrots as a group have been tolerant of urbanisation (Table 1). Other groups that seem to have benefited are the large honeyeaters and large carnivores with the smaller honeyeaters tending towards decline with increasing urbanisation. These trends run counter to the direction that would be expected if Museum collectors preferentially selected large and conspicuous birds. To understand why particular species are favoured or inhibited by urbanisation it is necessary to obtain more detailed data on fine-scale distributions in relation to habitat characteristics. The natural history of Sydney 235

3 Major Table 1. Presence/absence data on four groups of land birds that vary in their representation between pre-1900 and c Weights are expressed in grams Species Weight Parrots Turquoise Parrot yes no 40 Ground Parrot yes no 75 Scaly breasted Lorikeet no yes 86 Eastern Rosella no yes 99 Crimson Rosella no yes 129 Rainbow Lorikeet no yes 133 Australian Ringneck no yes 145 Australian King Parrot no yes 212 Gang gang Cockatoo no yes 257 Galah no yes 337 Yellow tailed Black Cockatoo no yes 700 Sulphur crested Cockatoo no yes 833 s Scarlet yes no 8 White fronted Chat yes no 13 White naped yes no 13 Fuscous yes no 17 Tawny crowned yes no 18 White eared yes no 20 Yellow tufted yes no 22 Regent yes no 42 Brown yes yes 11 Eastern Spinebill yes yes 11 Crescent yes yes 14 Yellow faced yes yes 16 White cheeked yes yes 20 New Holland yes yes 20 Lewin s yes yes 34 The Birds in Backyards project The Birds in Backyards website net is designed to draw attention to the decline in urban biodiversity, and to promote the role of individuals in sustainably managing human-dominated ecosystems. It aims is to enhance the persistence of the native birds that live where people live by increasing understanding of bird distributions and their habitat interactions. Participants are encouraged to carry out activities in their own backyards assisted by the web-based resources. The site has four main sections: Bird-finder, Surveys, Bird- Friendly Spaces and Featured Bird Groups (Figure 2). The Bird-finder tool returns a menu of up to 340 candidate species based on features selected by the observer using photographs, calls in mp3 format, descriptions and maps. Species Weight Brown headed no yes 13 White plumed no yes 19 Striped no yes 40 Noisy Miner no yes 59 Little Wattlebird no yes 62 Little Friarbird no yes 67 Blue faced no yes 108 Red Wattlebird no yes 111 Noisy Friarbird no yes 117 Large Brown Falcon yes no 530 carnivores Whistling Kite yes no 770 Pied Currawong yes yes 287 Laughing Kookaburra yes yes 340 Grey Butcherbird no yes 100 Pied Butcherbird no yes 149 Grey Currawong no yes 168 Pacific Baza no yes 220 Black shouldered Kite no yes 291 Australian Magpie no yes 317 Brown Goshawk no yes 454 Australian Raven no yes 557 White bellied Sea Eagle no yes 2630 Exotics House Sparrow yes yes 27 Spotted Turtle Dove yes yes 158 European Goldfinch no yes 16 Red whiskered Bulbul no yes 32 Common Starling no yes 78 Common Blackbird no yes 89 Common Myna no yes 116 Rock Dove no yes 300 Several simple, single-species surveys (e.g., a Channelbilled Cuckoo survey) provide an introduction to the research component of the Birds in Backyards project and as the participants confidence improves, they are encouraged to submit (via the website) surveys of the full complement of bird species that use their gardens, as well as information on garden structure. Surveyors are assisted by pop-up images and descriptions on the survey form of the most likely species to be encountered in different regions of Australia. Survey data are analysed regularly and feedback is provided both on the web-site, and to the individual providers via an membership list. The site also provides information on bird conservation and cultivating wildlife habitat in the sections Birdfriendly Spaces and Featured Bird Groups. As well as providing information on the status of birds and the 236 The natural histor y of Sydney

4 Monitoring change in the birds of Sydney Figure 2. Home page of the Birds in Backyards website: key threats, these sections provide practical guidelines on how to create habitat that favours the species that the research indicates are declining in urban areas. The information is strongly layered with both general design principles, as well as more detailed information such as plant lists of recommended species native to particular local government areas. Managed as a partnership between Birds Australia and the Australian Museum, the surveys began in September Participants can submit data from any location in Australia, but until 2007 promotion of the project had focused on urban areas of New South Wales. There is some flexibility in choice of survey methods for the backyard bird survey, with participants having the option of recording the birds present in a 20 min period, or keeping a list of all the species they observe in their survey area during a seven-day period. Emerging trends The backyard bird survey confirms the Atlas data in terms of identifying the species commonly encountered in Sydney (Figure 3). Parrots, large honeyeaters, large carnivores, and introduced species head the list of most common birds recorded in one-week garden surveys (n=384). Only five species of small honeyeater or insectivore are present in the top 30 bird species and even these have a relatively low probability of occurrence. The natural history of Sydney 237

5 Major Figure 3. The most common birds encountered in one-week Birds in Backyards surveys in Sydney (n=384). Values represent the percentage of surveys in which the species was seen. 238 The natural histor y of Sydney

6 Monitoring change in the birds of Sydney Because of the relatively large sample size, variability in the bird community with geographical region can be detected. For example, Australian King Parrots were recorded in 49 % of the gardens surveyed north of Sydney Harbour to Cowan Creek, but in only 1 % of gardens south of the harbour to Botany Bay (Figure 4). In contrast, Superb Fairy-wrens were more likely to be encountered south of the harbour. They were detected in 17 % of surveys south of the harbour, and only 2 % north of the harbour. A predominant cause of the decline of small birds in cities is commonly believed to be the rise of the Noisy Miner. This species was equally common north (88 %) and south (80 %) of the harbour. In surveys in which Noisy Miners were recorded, Superb Fairly-wrens were recorded in only 7 % of surveys, compared with 28 % of surveys where Noisy Miners were absent. This significant difference (χ 2 = 19.8, d.f. = 1, p < 0.000) provides correlative support for the role of aggressive behaviour of Noisy Miners having a negative impact on Superb Fairy-wrens. However, inferring cause of decline from correlations between species can be ambiguous because two species can be responding to particular environmental variables rather than to each other. For example, the negative correlation between the Australian King Parrot and the Superb Fairy-wren (χ 2 = 8.2, d.f. = 1, p = 0.004) reflects the fact that they tend to be found on opposite sides of the harbour. It is difficult to hypothesise a direct negative effect of one of these species on the other, but rather, a more likely explanation might lie in the variation in treecover evident from satellite photographs (Figure 1). Similarly, Superb Fairy-wrens were more likely (χ 2 = 9.8, d.f. = 1, p = 0.002) to be recorded in surveys with Indian Mynas (14 %) than in surveys from which they were absent (4 %). This certainly provides no support for the popular myth that Indian Mynas have a negative impact on small birds, but it is also unlikely that Indian Mynas are beneficial to Superb-Fairywrens as the positive correlation would imply. Instead, the positive relationship probably reflects the fact that both of these species commonly feed on residential lawned areas and thus have overlap in their habitat requirements. As well as identifying differences in local avifaunas, the Birds in Backyards survey data have the potential to provide information on changes in bird communities through time. For example, the single species survey on Channel-billed Cuckoos suggests a substantial increase in abundance from 2006 to This is consistent with a broader increase in both Pied Currawongs and Channel-billed Cuckoos, across NSW, over the last 20 years (Barrett et al. 2007). Three times as many first location records had been reported by late October in 2007 than in 2006 (Figure 5), but the single species surveys in the Birds in Backyards project are more difficult to interpret than complete backyard bird surveys, because they do not include absence data. However, participation by Birds in Backyards surveyors in full backyard surveys was comparable over the same period in the two years (69 surveys in 2006; 67 surveys in 2007), providing an overall index of surveyor activity. It would therefore seem reasonable to assume that there was comparable interest in the Channel-billed Cuckoo survey in the two years and that the increase in Channel-billed Cuckoo numbers is real. This can most simply be explained by changes in activity of its primary host. The primary host of the Channel-billed Cuckoos is the Pied Currawong (Figure 6; Higgins 1999), which did not breed in Sydney prior to the 1960s. Numbers of breeding Currawongs have been steadily increasing to the extent that they are now one of the most commonly reported species nesting in Sydney (Major 2003). It is quite conceivable that Channel-billed Cuckoos are tracking this increase, with a time-lag, and that the Birds in Backyards survey is monitoring an ongoing upward trend in the Channel-billed Cuckoo population of Sydney. Figure 3. The most common birds encountered in oneweek Birds in Backyards surveys in Sydney (n=384). Values represent the percentage of surveys in which the species was seen. Figure 5. Cumulative number of first sightings by individual observers of Channel-billed Cuckoos in the early part of the 2006 (circles) and 2007 (squares) breeding seasons. The natural history of Sydney 239

7 Major Figure 6. Number of observations recorded by Birds in Backyards volunteers of juvenile Channel-billed Cuckoos being fed by different host species. Acknowledgements I am grateful to Birds Australia for providing data from the New Atlas of Australian Birds and to the Australian Museum for providing data from the Ornithology Collection Database. Both organisations provided access to data from the Birds in Backyards database and I thank References Barrett, G., Silcocks, A., Barry, S., Cunningham, R. & Poulter, R The New Atlas of Australian Birds. Birds Australia (Royal Australasian Ornithologists Union), Melbourne. Barrett, G. W., A. F. Silcocks, Cunningham, R., Oliver, D.L., Weston, M.A. and Baker, J Comparison of Atlas data to determine the conservation status of bird species in New South Wales, with an emphasis on woodland-dependent species. Australian Zoologist 34: Currey, J.E.B. (ed) Reflections on the colony of New South Wales George Caley. Lansdowne Press Pty Ltd, Melbourne. Higgins, P.J. (ed) Handbook of Australian, New Zealand and Antarctic Birds. Vol. 4. Oxford University Press, Melbourne. Future planning The major objective of the Birds in Backyards project is to improve the prospect of maintaining a diverse bird community in urban areas such as Sydney. It aims to do this by fostering participatory research and providing resources that increase an appreciation of birds as well as the desire and information necessary to enhance habitats. Some local councils are embracing these ideas with actions including facilitating Birds in Backyards workshops for bush regenerators (e.g. Hornsby Council), planning demonstration streetside plantings (e.g. Woollahra Council), engaging schools in biodiversity audits (e.g. Baulkham Hills Shire Council), encouraging bird surveys (Bankstown Shire Council), and general publicity about wildlifefriendly gardening (e.g. Wollongong Shire Council). The Guidelines for urban bird habitat (www. birdsinbackyards.net/guidelines) and the on-line Birds in Backyards surveys are playing a key role in harnessing community action that hopefully will be reflected in future survey data. the Birds in Backyards steering committee: Kate Ravich, Holly Parsons, Charlotte Taylor, Judy Christie, Judy Harrington, Wojciech Dabrowka and Kris French. The manuscript was significantly improved by the constructive comments of two anonymous referees. Hoskin, E. S., Hindwood, K. A., & McGill, A. R The Birds of Sydney. Surrey Beatty and Sons Pty Ltd, Chipping Norton. Major, R.E Urban Currawongs. Nature Australia 27(9): North, A.J Nests and eggs of birds found nesting in Australia and Tasmania. Vol. 3. Australian Museum, Sydney. Recher, H. F The vertebrate fauna of Sydney. In: The city as a life system, edited by H. A. Nix, Proceedings of the Ecological Society of Australia, Vol. 7, Canberra. Waterhouse, R.D Some observations on the ecology of the Rainbow Lorikeet Trichoglossus haematodus in Oatley, South Sydney. Corella 21: The natural histor y of Sydney