NAWMP 2009 Assessment: monitoring and research on diving ducks within the SFBJV Region

Transcription

1 NAWMP 2009 Assessment: monitoring and research on diving ducks within the SFBJV Region Susan W. De La Cruz and John Y. Takekawa US Geological Survey, Western Ecological Research Center, San Francisco Bay Estuary Field Station U.S. Department of the Interior U.S. Geological Survey

2 Biological Assumptions I. Food energy is the primary need of wintering waterfowl..adequate foraging habitat will ensure that survival outside of the breeding season will not limit population growth Macroinvertebrate prey Intertidal and subtidal shoals, salt pond foraging habitat II. Several factors potentially limit access to adequate food and foraging areas: Habitat modification and loss in foraging areas Changing prey populations Disturbance III. Contaminants may limit populations independently of adequate food supply; food may be abundant but contaminated IV. Catastrophic mortality events (i.e. oil spills) are likely given the urban setting and population density

3 Monitoring of diving ducks in the SFBJV Region I. Midwinter present (transect based) II. Monthly surveys Oct Apr, semi-monthly, monthly, FWS Accurso Nov Mar, monthly, USGS WTA Study III. Salt pond surveys 1999 present North Bay 2002 present South Bay IV. Christmas bird count information on sloughs and rivers V. Various area or project based surveys

4 Greater Scaup (Aythya marila) 44% of scaup counted in lower Pacific Flyway winter in SFB SFB Scaup combined Flyway Total Scaup Lesser Scaup (Aythya affinis)

5 Canvasback (Aythya valisineria) Number wintering in the Bay has declined SFB Canvasback Flyway Total Canvasback Migration to Central Valley Changing prey populations

6 Surf Scoter (Melanitta perspicillata) 42% of scoters counted in lower Pacific Flyway winter in SFB SFB Total Scoters (Surf) Flyway Total Scoters (all spp)

7 Midwinter Database online Access database queries by species, year, region, transect Would provide data online for project managers Recently submitted proposal to SFBJV

8 Monthly aerial surveys Accurso 1992

9 Monthly aerial surveys

10 North Bay salt ponds present North Bay salt ponds Bufflehead Canvasback Ruddy Duck Scaup

11 South Bay salt ponds present South Bay salt ponds Bufflehead Canvasback Ruddy Duck Scaup

12 Research on diving ducks in SFBJV Region I. Foraging areas A. Habitat use B. Response to changing habitats: salt pond conversion II. Changing prey populations A. Diet and response to invasives B. Carrying capacity III. Disturbance A. Response to ferry traffic B. Trail use IV. Contaminants A. Effects on body condition B. Cross-seasonal seasonal effects V. Catastrophic events A. Oil spill - Cosco Busan

13 Factors influencing intertidal and subtidal foraging habitat Net Sediment Decline Mud flats decreasing at a rate of 14% per decade Tidal wetland restoration Sediment loss to wetland accretion? Salt pond conversion Climate change predicted loss of South and Central Bay mudflats due to sea level rise (Galbraith et al. 2002) Eelgrass loss and current restorations

14 Diving duck foraging areas Home Range Size (km 2 ) DEC JAN FEB MAR Median Depth (meters) Lesser Scaup Greater Scaup Nov Dec Jan Feb

15 Foraging depth preferences and available habitat Lesser scaup -.5 to 1m, Greater scaup 0 to 1.5m Available foraging area at a 1.2m tide = 32% of the Bay

16 Climate change How will foraging habitat change with: Sea level rise Freshwater flow Sediment change

17 Eelgrass prey densities and waterfowl foraging behavior Pilot study in conjunction with RB Audubon Evaluate waterbird foraging behavior in relation to invertebrate and fish availability Sampling based on grid system with known eelgrass and non-eelgrass grids Future questions: When do restored beds begin to approximate value of natural beds? What is the effect of herbivores on eelgrass health? (Ferson( 2007) observed behavior (%) 100% 75% 50% 25% 0% Behavior in Eelgrass AMCO BUFF FOTE HEGR RUDU SCAUP SUSC WCGR WEGU Preen Swim Rest Forage species/group

18 Response to end of salt production in North Bay ponds Number of Birds C. Diving Benthivores Number of Birds D. Canvasbacks North Bay salt ponds Benthivores crashed as water levels fell after salt-making ended. Estuary-wide surveys indicated emigration, not displacement. (Takekawa et al. 2001) Bufflehead Canvasback Ruddy Duck Scaup 2007 breach

19 Canvasback movements to the Delta and Sacramento Valley

20 Distribution of diving ducks in South Bay salt ponds during the winter Mean winter abundance and distribution,

21 Shoals project How will mudflat habitat change as salt ponds are breached? Measuring pre and post breach: Bathymetric change Invertebrate community composition and densities Waterbird community composition Waterbird foraging behavior and diet

22 Invasives: : Waterfowl response to changing prey species Corbula amurensis (overbite clam) Euryhaline bivalve introduced to northern SFB ~1986 Became dominant clam species in northern SF Bay How important is Corbula in diving duck diets? What is the prey value of Corbula compared to Macoma? Nichols et al. 1990

23 Diving duck winter diet 100 Percent of diving ducks consuming dominant prey items % of total birds CANV GRSC LESC Prey sizes Scaup <12 mm 20 0 Amphipods Isopods M. balthica C. amurensis Seeds Other Canv mm

24 Surf scoter diet differs among sub-bays bays Central North Suisun N Venerupis philippinarum Corbula amurensis Pyromaia tuberculata Musculista senhousia Hemigrapsus oregonensis Synidotea What is the role of herring roe in winter diet? Evaluating with isotopes clam siphons plant material Other

25 Clam depletion across winter Macoma densities remained similar throughout winter at most transects M. balthica fall spring Corbula densities declined significantly over winter at each transect Scaup foraging declined Number m * P. amurensis * * * fall spring Ca CC He MI SQ * * Poulton, V. K., J. R. Lovvorn, and J. Y. Takekawa Clam density and scaup feeding behavior in San Pablo Bay, California. Condor 104:

26 Prey Value Handling time and gross energy intake (kj/s) (Richman and Lovvorn 2004) Macoma Corbula Gross Energy (kj/s) Prey <6 mm long at 3 cm depth Prey 6-12 mm long at 3 cm depth Prey <6 mm long at 6 cm depth Prey /m Prey / m 2

27 Carrying capacity Recently funded through SF Foundation with SFBJV support Collaborative effort with Jim Lovvorn, SIU Individual-based models Daily Ration Models (Lovvorn and Baldwin 1996, Michot 1997) Spatial Depletion Models (Gill et al. 2001, Goss-Custard et al. 2003)

28 Carrying capacity: data available for modeling Macroinvertebrate density and patchiness cores BDAT online invertebrate datasets from several sampling efforts Prey preference and handling times Giving up thresholds Complications: Differentiating between fish and bird predators Capturing prey patchiness at several scales

29 Disturbance: Proposed increase in ferry numbers and routes Concern: Disturbance and displacement effects Objectives: 1) conduct on-board ferry surveys to assess speciesspecific response distances 2) examine waterbird behavior and abundance before and after watercraft in land-based surveys 3) document distribution of waterbirds along ferry routes with aerial surveys

30 Response to ferries differs by species Western or Clark s grebe 59 surveys on six existing ferry routes Average response distance = 300 m Total area of disturbance: behavioral response area (300 m) + variation in routes (200 m) = disturbance zone of 800 m Scoter Scaup Takekawa et al., in review

31 Ferry routes and disturbance effects Applied buffers to existing and proposed routes Existing ferry routes - total effect zone = 106km2 or 11% of SFB and 3% of foraging zone 10 proposed ferry routes increase effect zone to 23% of SFB and 18% of foraging zone

32 Trail use disturbance (mean +/- 1 SE) Canvasback: / m Scaup (lesser, greater combined): /-16.2 m Ruddy Duck: /- 9.6 m Bufflehead: / m White and Trulio 2008

33 Establish protected areas Restricted winter use in important foraging areas Minimizing impacts

34 Contaminants in SFB waterfowl Accumulated from benthic prey Corbula represents increased risk 3x more Selenium than Macoma (Linville et al. 2002) 22x more Cadmium than Macoma (Wallace et al. 2003, Wallace and Luoma 2003) Selenium and mercury elevated in scoters and scaup Human consumption advisory TMDL regulations Known effects of Se and Hg: Altered glutathione metabolism and oxidative stress Body condition Reproductive toxicity = most sensitive endpoint

35 Canvasback body condition: protein vs. selenium Takekawa et al. 2002

36 Scoter body condition and departure Poor condition can negatively influence: survival migration departure and timing breeding propensity reproductive success Wintering Site Departure (Ordinal Date) y = x R 2 = Mass (g) De La Cruz et al., submitted

37 Selenium concentrations higher in migrating than breeding area females [Se] ppm dry wt SFB Winter Haines Spring Yellowknife All Bays 16 May June 06

38 Selenium in egg and liver Liver Egg [Se] ppm dry wt YK June 1-4 YK June YK June 4 SFB Marked birds Mean arrival breeding area arrival date = 25 May Mean settling date = 27 May Egg effect concentration Liver effect concentration

39 Post Cosco-Busan research Survival and behavior of 3 treatment groups Rehabilitated Sham rehab Mark and release CDFG, OSPR Collaborative work: USGS, UC Davis OWCN, HSU, CDFG- OSPR

40 Preliminary Results: survival of 3 treatment groups after Cosco-Busan Takekawa,, De La Cruz (USGS), Ziccardi,, Massey (OWCN), Golightly (HSU), Henkel (OSPR), unpubl.. data

41 Research directions for the SFBJV Ecology of shoal habitats Continued work on wetland restoration effects on divers Foraging ecology of ruddy ducks and bufflehead Effect of climate change on foraging resources Effectiveness of protection zones for increasing available foraging habitat Value of restored versus natural eelgrass beds to waterfowl