MANAGEMNT OF CORMORANT COLONIES IN DENMARK

Transcription

1 AARHUS UNIVERSITET DCE / BIOSCIENCE MANAGEMNT OF CORMORANT COLONIES IN DENMARK THOMAS BREGNBALLE

2 Conflicts Demand for population control WILDLIFE ECOLOGY AND MANAGEMENT (BLOCK 2) CONSERVATION-RELATED DEMOGRAPHY AND POPULATION DYNAMICS

3 Option A: Avoid new colonisations Population control: - Scare away cormorants attempting to found new colonies Aim: - Control distribution - Avoid colonies in certain areas - Limit access to hitherto unexploited food resources WILDLIFE ECOLOGY AND MANAGEMENT (BLOCK 2) CONSERVATION-RELATED DEMOGRAPHY AND POPULATION DYNAMICS

4 Colonies exposed to management in 2015 AARHUS UNIVERSITET NATIONALT CENTER FOR MILJØ OG ENERGI Møde i Skarvforvaltningsgruppen, Kalø Example from september 2013 Nests removed Hov Røn (80 nests) Høje Sande (189 nests) Føns Vang (42 nests) Kidholmene (6 nests) Oiling af eggs Klægbanken (1407 nests) Agger Tange (30 nests) Ejerslev Røn (50 nests) Hirsholmene (158 nests) Kidholmene (35 nests) Treskelbakkeholm (280 nests) Vresen (115 nests) Peberholm (347 nests) Shooting in or near to co Rugård Sø Kidholmene (2 cormorants shot Føns Vang (62 cormorants sho

5 AARHUS UNIVERSITET DCE / BIOSCIENCE Proportion (%) of colonies surviving to year 1-4 after first colonization attempt No actions Actions Actions taken in the first and/or second year and in some cases in subsequent years as well 0 Yr 0 yr 1 yr 2 yr 3 yr 4 Year after colonization

6 AARHUS UNIVERSITET DCE / BIOSCIENCE Cumulated numbers of breeding pairs in new colonies where no actions were taken and in colonies exposed to management No actions Actions taken yr 0 yr 1 yr 2 yr 3 yr 4 Year after colonization

7 XX Option B Population control by reducing th production of young - Oiling of eggs WILDLIFE ECOLOGY AND MANAGEMENT (BLOCK 2) CONSERVATION-RELATED DEMOGRAPHY AND POPULATION DYNAMICS

8 AARHUS UNIVERSITET Numbers of nests exposed to management in Denmark (mainly by egg oiling) Reder udsat for indgreb TITEL PÅ PRÆSENTATION NAVN NAVNESEN SEPTEMBER 2011

9 AARHUS UNIVERSITET NATIONALT CENTER FOR MILJØ OG ENERGI Proportion (%) of the breeding Møde i Skarvforvaltningsgruppen, Kalø population exposed to management in Denmark % af alle reder udsat for indgreb 12. september

10 The number AARHUS UNIVERSITET of nests exposed to management xx NATIONALT CENTER FOR MILJØ OG ENERGI Møde i Skarvforvaltningsgruppen, Kalø has declined because breeding numbers have declined in some of the areas where egg oiling was extensive 12. september 2013 Course in Wildlife Ecology and Management, spring 2011, Block 5: Cormorants: Population ecology, modelling and management

11 xx AARHUS UNIVERSITET NATIONALT CENTER FOR MILJØ OG ENERGI Møde i Skarvforvaltningsgruppen, Kalø 12. september % of the nests exposed to management were oiled in 2015 Course in Wildlife Ecology and Management, spring 2011, Block 5: Cormorants: Population ecology, modelling and management

12 Ringkøbing Fjord AARHUS UNIVERSITET NATIONALT CENTER FOR MILJØ OG ENERGI Møde i Skarvforvaltningsgruppen, Kalø 12. september 2013 Course in Wildlife Ecology and Management, spring 2011, Block 5: Cormorants: Population ecology, modelling and management

13 Antal reder AARHUS UNIVERSITET DCE / BIOSCIENCE 19. AUGUST 2015 Development in Ringkøbing Fjord Med Oiling oliering of eggs Uden No oiling oliering THOMAS BREGNBALLE

14 Rønland Sandø Course in Wildlife Ecology and Management, spring 2011, Block 5: Cormorants: Population ecology, modelling and management WILDLIFE AARHUS ECOLOGY UNIVERSITY, AND MANAGEMENT National Environmental (BLOCK 2) CONSERVATION-RELATED Research Institute DEMOGRAPHY AND POPULATION DYNAMICS

15 Example of long-term effects Oiling of eggs No oiling WILDLIFE ECOLOGY AND MANAGEMENT (BLOCK 2) CONSERVATION-RELATED DEMOGRAPHY AND POPULATION DYNAMICS

16 Long-term effects Breeding numbers may start to decline after several years of intensive egg oiling emigration of unsuccessful breeders lack of new recruits after 2-5 years However, immigration may increase if food conditions are favourable Course in Wildlife Ecology and Management, spring 2011, Block 5: Cormorants: Population ecology, modelling and management WILDLIFE AARHUS ECOLOGY UNIVERSITY, AND MANAGEMENT National Environmental (BLOCK 2) CONSERVATION-RELATED Research Institute DEMOGRAPHY AND POPULATION DYNAMICS

17 A few conclusions actions in colonies The success in avoiding successful establishment of new colonies seems to vary depending on: How quickly actions are taken (most efficient if done in the very first years and early in the season, i.e. before incubation starts) How intensive actions are (lowest chance of return if scaring activities are intensive and repeated) The availability of alternative breeding sites Regulation of the size and distribution of the breeding population by oiling of eggs is difficult and there is no guarantee of success despite continuing oiling year after year (new birds may immigrate if food is easily available) Course in Wildlife Ecology and Management, spring 2011, Block 5: Cormorants: Population ecology, modelling and management WILDLIFE AARHUS ECOLOGY UNIVERSITY, AND MANAGEMENT National Environmental (BLOCK 2) CONSERVATION-RELATED Research Institute DEMOGRAPHY AND POPULATION DYNAMICS

18 Tools to limit cormorant numbers Staging and wintering areas Shooting WILDLIFE ECOLOGY AND MANAGEMENT (BLOCK 2) CONSERVATION-RELATED DEMOGRAPHY AND POPULATION DYNAMICS

19 01-aug 06-aug 11-aug 16-aug 21-aug 26-aug 31-aug 05-sep 10-sep 15-sep 20-sep 25-sep 30-sep 05-okt 10-okt 15-okt 20-okt 25-okt 30-okt 04-nov 09-nov 14-nov Antal dagrastende Shooting to scare cormorants - within season effects scaring near the main night roost in a Danish fjord

20 Numbers counted/shot Shooting to control numbers - between season effects 8000 example from Bavaria Counted Shot Winter season

21 A few conclusions shooting outside breeding The chances of success in reducing numbers at the local or regional level by shooting is low under most circumstances. This is because cormorants tend to move extensively among areas new and naive birds are likely to appear later in the season or following years, especially of the area is attractive. Shooting can be used a successful tool to scare cormorants away from local areas. This may, however, require that the scaring is carried out close to the night roost(s). The chance of success is likely to depend on the time of the season and the availability of alternative sites in the area/region. Course in Wildlife Ecology and Management, spring 2011, Block 5: Cormorants: Population ecology, modelling and management WILDLIFE AARHUS ECOLOGY UNIVERSITY, AND MANAGEMENT National Environmental (BLOCK 2) CONSERVATION-RELATED Research Institute DEMOGRAPHY AND POPULATION DYNAMICS

22 The relevant 1 million Euro question Will reduced consumption lead to higher catches? Will fewer cormorants take fish from pound nets? Will fewer smolt of salmon and trout be predated? Course in Wildlife Ecology and Management, spring 2011, Block 5: Cormorants: Population ecology, modelling and management AARHUS UNIVERSITY, National Environmental Research Institute

23 Losses caused by Cormorants Numbers of cormorants causing damage in an area in relation to overall numbers % reduction 20 50% reduction Numbers of Cormorants in region Course in Wildlife Ecology and Management, spring 2011, Block 5: Cormorants: Population ecology, modelling and management AARHUS UNIVERSITY, National Environmental Research Institute

24 Cormorants will always go to attractive feeding sites sites Course in Wildlife Ecology and Management, spring 2011, Block 5: Cormorants: Population ecology, modelling and management WILDLIFE AARHUS ECOLOGY UNIVERSITY, AND MANAGEMENT National Environmental (BLOCK 2) CONSERVATION-RELATED Research Institute DEMOGRAPHY AND POPULATION DYNAMICS

25 AARHUS UNIVERSITY DEPARTMENT OF BIOSCIENCE, WILDLIFE ECOLOGY GROUP WILDLIFE ECOLOGY AND MANAGEMENT MANAGEMNT OF CORMORANTS IN DENMARK UNI VERSITET

26 The national management plan in Denmark 1992: The first plan was developed 1994: Supplementary rules aimed at limiting the numbers of successful new colonisations 2002: The second plan was developed Oiling of eggs in a few selected ground-nesting colonies initiated to limit numbers in particular areas 2009: Revised version of the 2002 plan 2016: Revised version of the 2009 plan More focus on areas with particular problems Permission to scare on certain night roosts Course in Wildlife Ecology and Management, spring 2011, Block 5: Cormorants: Population ecology, modelling and management WILDLIFE AARHUS ECOLOGY UNIVERSITY, AND MANAGEMENT National Environmental (BLOCK 2) CONSERVATION-RELATED Research Institute DEMOGRAPHY AND POPULATION DYNAMICS

27 Denmark: Prevention of serious damage Salmon Studies suggested that % of the Salmon smolt in Skjern River was predated by cormorants before reaching the Atlantic Ocean. To reduce the loss of smolt, cormorant eggs in all nests (except nests) were oiled annually in the local fjord. See other slides. Flounder Studies suggested that cormorants in some years took a fairly large proportion of juvenile flounder, at least in certain areas. To reduce predation, cormorant eggs in all nests Course (except in Wildlife Ecology and Management, spring nests) 2011, Block were 5: Cormorants: oiled Population annually ecology, modelling and in management one of the colonies. See other slides. WILDLIFE AARHUS ECOLOGY UNIVERSITY, AND MANAGEMENT National Environmental (BLOCK 2) CONSERVATION-RELATED Research Institute DEMOGRAPHY AND POPULATION DYNAMICS

28 Denmark: Prevention of serious damage To handle all worries for further increases in losses of fish species of particular concern/value In the parts of Denmark that have been designated as being of particular value to juvenile fish of species of particular high priority, permission has been given to oil eggs in existing (and old) ground nesting colonies In most parts of Denmark but depending on the wish of the land owner, permission has been given to try to avoid successful establishment of new colonies by oiling eggs in new ground nesting colonies by scaring away cormorants early in the breeding season Course in Wildlife Ecology and Management, spring 2011, Block 5: Cormorants: Population ecology, modelling and management WILDLIFE AARHUS ECOLOGY UNIVERSITY, AND MANAGEMENT National Environmental (BLOCK 2) CONSERVATION-RELATED Research Institute DEMOGRAPHY AND POPULATION DYNAMICS

29 Denmark: Actions for other reasons To limit losses of trees of particular value In a few cases where landowners have had concerns about losses of trees of particular value, permissions have been given to try to scare away breeding cormorants. Actions have not been taken due to worries about eutrophication. Course in Wildlife Ecology and Management, spring 2011, Block 5: Cormorants: Population ecology, modelling and management WILDLIFE AARHUS ECOLOGY UNIVERSITY, AND MANAGEMENT National Environmental (BLOCK 2) CONSERVATION-RELATED Research Institute DEMOGRAPHY AND POPULATION DYNAMICS

30 Denmark: Criteria for serious damage No fixed criteria for serious damage have been applied before taking decisions about permissions for taking action against cormorants. The evidence for serious damage has ranged from worries that losses affected catches or survival to catchable sizes to a few cases where studies documented or indicated that cormorants affected the surivival of juvenile or adult fish. Course in Wildlife Ecology and Management, spring 2011, Block 5: Cormorants: Population ecology, modelling and management WILDLIFE AARHUS ECOLOGY UNIVERSITY, AND MANAGEMENT National Environmental (BLOCK 2) CONSERVATION-RELATED Research Institute DEMOGRAPHY AND POPULATION DYNAMICS

31 Denmark: What is needed for deciding on actions The Nature Agency has according to the national management plan a guidance on whether or not to give permission to take actions against foraging, roosting and/or breeding cormorants. The amount of evidence needed would then to some extent depend on whether the local area in question is located inside or outside one of the areas of special concern. But also on such factors as whether or not a) it is located within or near to a bird protection area (e.g. some of the NATURA 2000 areas), b) other species of birds will be affected by the actions that could be neccessary to use in order to scare away cormorants or regulate their numbers. Course in Wildlife Ecology and Management, spring 2011, Block 5: Cormorants: Population ecology, modelling and management WILDLIFE AARHUS ECOLOGY UNIVERSITY, AND MANAGEMENT National Environmental (BLOCK 2) CONSERVATION-RELATED Research Institute DEMOGRAPHY AND POPULATION DYNAMICS

32 Denmark: What is needed for deciding on actions Standard permissions include: Owners of fishing gear are always allowed to shoot an unlimited number of cormorants present within 1000 m of the their actively fishing fishing gear Landowners that would like to avoid that cormorants are successful in forming a new colony on their land will usually get permission to try to avoid this. However, it may depend on the location of the site in question. The landowner may get assistance from the Nature Agency with the scaring or oiling of eggs. Course in Wildlife Ecology and Management, spring 2011, Block 5: Cormorants: Population ecology, modelling and management WILDLIFE AARHUS ECOLOGY UNIVERSITY, AND MANAGEMENT National Environmental (BLOCK 2) CONSERVATION-RELATED Research Institute DEMOGRAPHY AND POPULATION DYNAMICS

33 Denmark: What is needed for deciding on actions Extra-ordinary actions: Some kind of evidence for serious damage would probably be needed in case the request would require actions to be taken in already existing breeding colonies. Course in Wildlife Ecology and Management, spring 2011, Block 5: Cormorants: Population ecology, modelling and management WILDLIFE AARHUS ECOLOGY UNIVERSITY, AND MANAGEMENT National Environmental (BLOCK 2) CONSERVATION-RELATED Research Institute DEMOGRAPHY AND POPULATION DYNAMICS

34 Denmark: The kind of measures The standard measures that are applied in Denmark includes: Shooting some birds to increase the effect of scaring by use of shots (near to fishing gear, when birds try to form new colonies, birds foraging at certain sites, birds at certain roosts) Oiling of eggs at 2 weeks intervals throughout the breeding season Various non-lethal scaring devices. Course in Wildlife Ecology and Management, spring 2011, Block 5: Cormorants: Population ecology, modelling and management WILDLIFE AARHUS ECOLOGY UNIVERSITY, AND MANAGEMENT National Environmental (BLOCK 2) CONSERVATION-RELATED Research Institute DEMOGRAPHY AND POPULATION DYNAMICS

35 Denmark: Requirements of reporting The standard requirement includes: Report the number of individuals shot Report the effect of your actions Report the number of nests exposed to egg oiling Course in Wildlife Ecology and Management, spring 2011, Block 5: Cormorants: Population ecology, modelling and management WILDLIFE AARHUS ECOLOGY UNIVERSITY, AND MANAGEMENT National Environmental (BLOCK 2) CONSERVATION-RELATED Research Institute DEMOGRAPHY AND POPULATION DYNAMICS

36 Denmark: Have the measures been effective The success in using the various measures has varied, depending on a range of factors related to such matters as: The effort (frequency and intensity) Timing of the actions (e.g. when during the breeding season) The location of the site in relation neighbouring sites of value to cormorants movements of birds Availability of fish more difficult to keep cormorants from very attractive feeding sites etc. see also other slides. Course in Wildlife Ecology and Management, spring 2011, Block 5: Cormorants: Population ecology, modelling and management WILDLIFE AARHUS ECOLOGY UNIVERSITY, AND MANAGEMENT National Environmental (BLOCK 2) CONSERVATION-RELATED Research Institute DEMOGRAPHY AND POPULATION DYNAMICS

37 Denmark: Is there a need for cooperation among Baltic Sea states Cooperation would be of great value to learn from each other on a number of cormorant conflict related issues for conducting studies of efficiency of various actions aimed at limiting damage the countries have many similar types of problems but it is often a problem to find sufficient funding in a single country. Countries that share problems could co-fund studies and demonstration projects for developing techniques to study the extent of damage on fish populations/fish chatches Course in Wildlife Ecology and Management, spring 2011, Block 5: Cormorants: Population ecology, modelling and management WILDLIFE AARHUS ECOLOGY UNIVERSITY, AND MANAGEMENT National Environmental (BLOCK 2) CONSERVATION-RELATED Research Institute DEMOGRAPHY AND POPULATION DYNAMICS

38 Denmark: Is there a need for cooperation among Baltic Sea states In a number of cases cooperation would be neccessary if countries would like to attempt to limit the damage occuring at larger water bodies outside the breeding season by reducing the number of individuals. Thus cormorants are dispersing widely after the breeding season and some birds from southern breeding populations disperse north during post-breeding. Control of overall population sizes will, however, easily become costly and the effects in terms of reduced losses are likely to be very difficult to predict. Course in Wildlife Ecology and Management, spring 2011, Block 5: Cormorants: Population ecology, modelling and management WILDLIFE AARHUS ECOLOGY UNIVERSITY, AND MANAGEMENT National Environmental (BLOCK 2) CONSERVATION-RELATED Research Institute DEMOGRAPHY AND POPULATION DYNAMICS