Population Size and Winter Distribution of Eastern American Oystercatchers

1. Population Size and Winter Distribution of Eastern American Oystercatchers An Evaluation of Aerial Surveys To Meet the Monitoring Goals of the U.S. Shorebird Plan Stephen Brown, Shiloh Schulte, Brian Harrington, Jon Bart, Brad Winn, and Marshall Howe

2. American Oystercatcher U.S. Shorebird Plan: • Population size estimate: 7500 birds, high risk due to low number • Conservation needs: • Survey wintering population • Band resighting study to determine migration patterns • Determination of high priority habitat • Coordinated efforts required: AMOY working group formed

3. American Oystercatcher Category: High Priority Focal species: Beachfront Population Trend = 3 Relative Abundance = 5 Threats Breeding = 4 Threats Non-breeding = 4 Breeding Distribution = 3 Non-breeding Dist. = 4 Population Estimates Current Target Haematopus palliatus 7,500 ? (Status unknown) *Low population, vulnerable to wintering habitat loss

5. Range of the American Oystercatcher From Nol and Humphrey 1994

6. 37. Gulf Coastal Prairie 37. Gulf Coastal Prairie BCR 30: New-England/ Mid-Atlantic Coast American Oystercatcher Survey Coverage BCR 27: Southeastern Coastal Plain BCR 31: Peninsular Florida BCR 37: Gulf Coastal Prairie

7. American Oystercatcher Survey Methods • Estimates of flock size • Stratified sampling • Aerial photography (Digital SLR, 6.1 MP, 300 mm image stabilized lens) for detection rate within flocks • Ground counts for flock detection rates • Survey window High Tide +/- 2 Hours • Videography tests

8. Survey Zones • High quality habitat types • Known roost sites • Shell rakes, sand spits, etc. • Complete survey of all locations identified • Intertidal marsh habitats • States, broken into blocks • Random subsample surveyed completely • Barrier beach habitats • Survey all in random blocks • Survey all other areas opportunistically

9. Strata Used to Estimate Population Size • Flocks in high-quality habitat counted on the ground or in photographs • No sampling error • Flocks in high-quality habitat counted visually from the air • Detection rate for birds in flocks • Flocks on barrier beaches • Detection rate for flocks • Detection rate for birds in flocks • Flocks in low-quality habitat

10. Detection Rates • Detection rate for flocks • Calculated from ground counts • Applied to high quality habitat areas with no ground counts • Detection rate for birds within flocks • Calculated with photographs • Applied to high quality habitat area flocks with no photograph

11. American Oystercatcher Survey Zones

18. American Oystercatcher Roost Site Locations From Aerial Surveys

19. Survey Coverage by State

20. Detection Rate : Flock Size Estimates R2=0.9761 N=87 Mean Estimate/Count=0.91 (SE = 0.002)

21. Detection Rates: Flocks

22. Numbers of Birds Recorded By State

23. Population Estimate for Eastern American Oystercatchers Final Population Estimate = 10,971 ± 298

24. Oystercatcher Roost Site Habitat Use and Availability

25. Acknowledgments • USGS SSP Program • USFWS Region 5 • Atlantic Coast Joint Venture • National Fish and Wildlife Foundation • Scott Johnston, Andrew Milliken • Catherine Wightman • Ground count crews: Barry Truitt, Alex Wilke, Felicia Sanders, Nancy Douglas, David Allen, Amanda Dey, David Mizrahi

26. Acknowledgments, cont’d New Jersey Division of Fish and Wildlife Virginia Department of Game and Inland Fisheries North Carolina South Carolina Department of Natural Resources Georgia Department of Natural Resources Florida Fish and Wildlife Commission Alabama Wildlife and Freshwater Fisheries Division Texas Parks and Wildlife The Nature Conservancy National Audubon Society New Jersey Audubon Society Audubon North Carolina Audubon of Florida Houston Audubon Society Cape Romain National Wildlife Refuge Grand Bay National Estuarine Research Reserve