Density-dependence in reproduction and survival :

1. Linkages with chum salmon Density-dependence in reproduction and survival: Kyle Elliott, University of Manitoba John Elliott, Laurie Wilson, Environment Canada Ken Stenerson, Kruger Forest Products Elliott et al 2011 J Wildl Manage On line N. Rich

2. 100,000 1,000 2000 1600 Bald Eagle Populations • 1600 North Am popln 500,000+ ? • 1600Popln decline- persecution • 1780 & habitat destruction • 1780 25,000 - 75,000 birds • 1940 BAEA Protect Act - some recovery • 1947 Organochlorine erabegins • 1957 Reprod. failuredocumented in Florida • 1960 < 450 nesting pairs in lower U.S. • 1973 ESA in U.S., endang. status in some Cdn prov. • 1975DDT& other OC-pestic. useminimal (chlordane?) • 1977 PCBs regulated (TSCA, CEPA) • 1991 Lead shot ban for waterfowl in U.S. • 1995 Endangered tothreatened status> 5,000

4. Objectives • Analyze long term data on eagles breeding and wintering on south coast of BC • Identify factors / mechanisms influencing trends.

5. Methods Counted eagles Breeding season by helicopter Occupied Territories Productivity Winter season with volunteers Christmas Bird Count Vancouver Raptor Census Coastal Waterbird Survey Midwinter Bald Eagle Count Modelling Leslie matrix Density-dependence in mortality and reproduction

6. Sampling Locations (1973-2010) (1-12) = CBC Loc. = Breeding Counts = Salmon Spawning = Raptor Census Squamish Harrison Study Area CBC Loc. Km

7. Breeding territories – Lower Fraser Valley

8. Reproductive SuccessSubadult Counts●Subadult Mortality Density-dependence …but not through site-dependence

9. Wintering eagle population on the south coast No. eagles wintering of south coast has increased to carrying capacity

10. Average no. of eagles counted at sites along Pacific coast N. Rich Weeks after Sept. 1

11. Adjusted eagle numbers on south coast of BC Increase with colder weather in Alaska

12. Eagle use days increase with chum availability at Squamish N. Rich

13. Percentage prey items in diet seasonally

14. Bald Eagle Mortality: Percent by month (white) and corrected for total present (dark)

15. Causes of death for bald eagles, BC, 1989-2005 Subadults Adults

16. Loss of Salmon Stocks Extinct High Risk Moderate Risk Special Concern Unthreatened Columbia River Basin Fraser River Basin Source: Nehlsen et al., 1991 and Stanley et al., 1996

17. 400+ eagles spend time at the Delta landfill in winter 95% of time resting or drinking; <5% foraging or feeding* *Elliott, K et al Wilson Bull, 2006

18. AIC ranking of models for bald eagle populations, SW BC, 1973-2010 • Alaska = Alaska Temperature • BC = BC Temperature • Observer = Number of observers per count • βR = Density-dependence in reproduction • βS = Density-dependence in survival

19. “Me and my gang” Impact on “prey” species? • Bald eagles will harass and prey on colonial nesting species: • Great blue heron (Salish Sea—Vennesland and Butler 2005). • Double-crested Cormorant (Salish Sea, Middleton Island—Moul and Gebauer 2002). • Glaucous-winged Gull (Salish Sea—Sullivan et al. 2002, Hayward et al. 2010). • Dusky Canada Goose (Copper River—Anthony et al. 2004). • Common Murre (Middleton, Triangle, Tatoosh Island—Hipfner et al. 2001, Parrish et al. 2000). • Black-legged Kittiwake (Middleton Island)

20. Summary • South coastal BC eagle breeding and wintering population increased 4-6X over past 4 decades. • Numbers of breeding and winter birds now “stabilized” • Density-dependence in reproduction and survival (model) • Years with reduced salmon & cold (Alaska) winters leads to reduced late winter survival & breeding females in poor body condition. Elliott et al 2011 J Wildl Manage online

21. THANKS! • Sandi Lee and Wayne Gardner for counting winter eagles • Many volunteers F. Kovalchuk

22. Study Area Food supply (Elliott et al 2006, JRR) Canada USA Pinchi Lk. Reference Lks. British Johnstone St. Columbia Clayoquot Sd. Barkley Sd. Powell River SE Vancouver I. • Vancouver Fraser Delta • Seattle 0 40 80 120 160 Lower Fraser Valley Kilometres 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 Young / occupied nest Bald Eagle Nest Success Elliott et al.1998. JWM

23. Wintering eagles Double-survey techniques show >90% repeatability

24. British Columbia’s eagles • British Columbia (breeding and winter): 30% increase from 1960s to 1980s (Vermeer et al. 1989) • British Columbia (winter): “Either stable or increasing” (Blood and Anweiler 1994) • British Columbia (winter): “Generally stable” (Campbell et al. 1990) • British Columbia (winter): No change 1982-1997 (Buehler 2000) • Washington (breeding): Increased 10.1% per year 1980-1998 (Watson et al. 2002) Increased 1962-1995, stable to 1998 in San Juans (Watson et al. 2002) • Washington (winter, Skagit): Doubled 1987-1992, then stable (Dunwiddie and Kuntz 2001)

25. Issue of native harvest of eagles for ceremonial items

26. 2.4 r = 0.63 2 1.6 Young/Occ. Terr. 1.2 0.8 North of mill South of mill 0.4 Barkley Sound 0 500 1000 1500 2000 2500 3000 3500 4000 Prey energy/day/eaglet Prey energy and productivity at BC coastal eagle nests

27. Prey delivery rate and weather, SW BC eagles (Elliott et al. 2005. J Rap Res) Elliott et al. 2005. JRR

28. Indication: Areas lacking an adequate and stable prey base, and which are subject to regular episodes of wet spring weather are likely to contain Bald Eagle sink populations

29. Bald eagles and landfills Elliott et al. 2006. Wilson J Ornithol Panoramia

30. Thyroid Hormones • Regulate growth and development, particularly neurological system • Important to immune system function • Regulate metabolism • Cardiovascular effects deiodinases