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

American Oystercatcher 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 U.S. Shorebird Plan:

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 EstimatesCurrentTarget Haematopus palliatus7,500? (Status unknown) *Low population, vulnerable to wintering habitat loss

Range of the American Oystercatcher From Nol and Humphrey 1994

International Shorebird Survey Sites: Atlantic and Gulf Coasts Coastal coverage is considerable, but data from many sites is limited

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

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

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

Strata Used to Estimate Population Size 1.Flocks in high-quality habitat counted on the ground or in photographs -No sampling error 2.Flocks in high-quality habitat counted visually from the air -Detection rate for birds in flocks 3.Flocks on barrier beaches -Detection rate for flocks -Detection rate for birds in flocks 4.Flocks in low-quality habitat

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

American Oystercatcher Survey Zones

American Oystercatcher Roost Site Locations From Aerial Surveys

Survey Coverage by State

R 2 = N=87 Detection Rate : Flock Size Estimates Mean Estimate/Count=0.91 (SE = 0.002)

Detection Rates: Flocks

Numbers of Birds Recorded By State

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

Oystercatcher Roost Site Habitat Use and Availability

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

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