Long-term studies of Guillemots on Skomer Island Tim Birkhead and Ben Hatchwell

1. Long-term studies of Guillemots on Skomer Island Tim Birkhead and Ben Hatchwell University of Sheffield, Sheffield UK

2. Communal care ~ alloparental care GUILLEMOT Long-lived (~ 25 years) Monogamous, well almost Intensely social Breeds at high densities

3. Conditions in the North Sea

6. Skomer Island

7. ACKNOWLEDGEMENTS Wildlife Trust of South and West Wales Countryside Council for Wales Natural Environment Research Council University of Sheffield Skomer wardens and their partners Boatmen Numerous field assistants over 35 years

8. Changing Fortunes

9. Whole-island counts since 1962 Number of guillemots

10. Wick Corner Ledge 1930s photo by R M Lockley

11. Wick Corner Ledge 1973

12. Wick Corner Ledge 2005 - almost full again

13. Overall, a substantial increase in numbers since 1980 but still a long way off 1890s or 1930s levels

14. The Long-Term study of Guillemots on Skomer Aims: To understand what determines the numbers of guillemots 1. Annual survival - of adults & immature birds 2. Age of first breeding 3. Breeding success 4. Chick diet and feeding rate 5. Identify the factors affecting these

15. Main Study Site on Skomer

16. The Amos

17. The Amos in 2008

18. The Amos in 1972

20. Field assistants Training: to work independently, consistently and accurately

21. Adult Survival Catch adults + give individual colour rings

22. The ideal….

23. The reality….

24. Measuring Immature survival Catching and marking 300 chicks each year 9000 chicks ringed so far

26. Over 9000 guillemot chicks ringed since 1972

27. Breeding Success

28. A sample of 100-200 pairs each year and record the proportion of pairs successfully rearing a chick

29. Chick diets and feeding rates

30. Collecting data 1. Daily observations: re-sightings of marked birds 2. 500 hours field work per season 3. PDA is very efficient

32. Data analysis: detailed statistical modelling Steve Votier

33. Sprat 3/day What have we found out? Adult survival 87-97% 7 years Age of first breeding Immature survival High, but variable Breeding success High - 70-90% Chick diet

34. Adult survival is the most important parameter

35. Effect of climate change on guillemot population parameters

36. North Atlantic Oscillation (NAO) a phenomenon associated with winter fluctuations in temperatures, rainfall and storminess. Positive NAO = westerly winds are stronger or more persistent, northern Europe tends to be warmer and wetter than average. Negative NAO = westerly winds weaker or less persistent, northern Europe tends to be colder and drier.

37. 1950 1980 2000 From T. Osborn, Climate Research Unit, University of East Anglia NAO NAO: A general increase since 1980 but very variable

38. Adult guillemot survival decreases significantly with NAO

39. The Erika December 1999, 10,000 tons Brittany, Northern France OIL

40. Oiling incidents significantly reduce survival Annual adult survival

41. Adult Survival Under ‘normal’ conditions adult survival is 93-97% When survival is 93% average breeding lifespan is 14 years When survival is 97% average breeding lifespan is 33 years Oil incidents reduce survival to 87% = 7 year lifespan

42. Productivity (breeding success)

43. Breeding is later when the NAO index is higher

44. Breeding success is lower in years when breeding is late 0.90 Breeding Success 0.60 Mid May Early May LAYING DATE

45. CLIMATE? FOOD AVAILABILITY OVER-FISHING? + + + IMMATURE SURVIVAL ADULT SURVIVAL PRODUCTIVITY NAO OIL Negative effects

46. Long term monitoring of population parameters provides 1. A much more sensitive assay of events than counts alone 2. Early warning system 3. Better understanding of the biology & reasons for change 4. A clear signal to the public of concern for populations

47. The End