Population Size and Winter Population Size and Winter Distribution of Eastern Distribution of Eastern

American OystercatchersAmerican Oystercatchers

An Evaluation of Aerial Surveys To Meet the An Evaluation of Aerial Surveys To Meet the Monitoring Goals of the U.S. Shorebird PlanMonitoring Goals of the U.S. Shorebird Plan

Stephen Brown, Shiloh Schulte, Brian Harrington, Stephen Brown, Shiloh Schulte, Brian Harrington, Jon Bart, Brad Winn, and Marshall HoweJon 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 American OystercatcherOystercatcherCategory: High PriorityFocal species: Beachfront

Population Trend = 3Relative Abundance = 5Threats Breeding = 4Threats Non-breeding = 4Breeding Distribution = 3Non-breeding Dist. = 4

Population Estimates Current TargetHaematopus palliatus 7,500 ? (Status unknown)

*Low population, vulnerable to wintering habitat loss

Range of the AmericanOystercatcher

From Nol and Humphrey 1994

American American Oystercatcher Oystercatcher

Survey Survey CoverageCoverage

BCR 30:New-England/Mid-Atlantic Coast

BCR 27:Southeastern Coastal Plain

BCR 37: Gulf Coastal Prairie

BCR 31:Peninsular Florida

American Oystercatcher American Oystercatcher Survey MethodsSurvey Methods

• Estimates of flock sizeEstimates of flock size• Stratified samplingStratified sampling• Aerial photography (Digital SLR, 6.1 Aerial photography (Digital SLR, 6.1

MP, 300 mm image stabilized lens) MP, 300 mm image stabilized lens) for detection rate within flocksfor detection rate within flocks

• Ground counts for flock detection Ground counts for flock detection ratesrates

• Survey window High Tide +/- 2 HoursSurvey window High Tide +/- 2 Hours• Videography testsVideography tests

Survey ZonesSurvey Zones• High quality habitat typesHigh quality habitat types

– Known roost sitesKnown roost sites– Shell rakes, sand spits, etc.Shell rakes, sand spits, etc.– Complete survey of all locations identifiedComplete survey of all locations identified

• Intertidal marsh habitatsIntertidal marsh habitats– States, broken into blocks States, broken into blocks – Random subsample surveyed completelyRandom subsample surveyed completely

• Barrier beach habitatsBarrier beach habitats– Survey all in random blocksSurvey all in random blocks– Survey all other areas opportunisticallySurvey all other areas opportunistically

Strata Used to Estimate Strata Used to Estimate Population SizePopulation Size

1.1. Flocks in high-quality habitat counted on the Flocks in high-quality habitat counted on the ground or in photographsground or in photographs

- No sampling errorNo sampling error 2.2. Flocks in high-quality habitat counted Flocks in high-quality habitat counted

visually from the air visually from the air - Detection rate for birds in flocksDetection rate for birds in flocks

3.3. Flocks on barrier beachesFlocks on barrier beaches- Detection rate for flocksDetection rate for flocks- Detection rate for birds in flocks Detection rate for birds in flocks

4.4. Flocks in low-quality habitatFlocks in low-quality habitat

Detection RatesDetection Rates

•Detection rate for flocksDetection rate for flocks

- Calculated from ground countsCalculated from ground counts

- Applied to high quality habitat areas Applied to high quality habitat areas with no ground countswith no ground counts

•Detection rate for birds within flocksDetection rate for birds within flocks

- Calculated with photographsCalculated with photographs

- Applied to high quality habitat area Applied to high quality habitat area flocks with no photographflocks with no photograph

American Oystercatcher Survey Zones

American Oystercatcher Roost Site Locations From Aerial Surveys

Survey Coverage by State

State % Intercoastal tidal zone surveyed

% Barrier Beach surveyed

% High Quality Habitats surveyed

Survey Blocks with 80% or better coverage

Mid Atlantic 70 100 100 12 of 16North Carolina 80 70* 100 30 of 37South Carolina 60 100 100 14 of 23Georgia 50 90* 100 7 of 17West Florida 55 95 100 28 of 46Alabama 70 100 100 4 of 5Mississippi 85 100 100 6 of 6Louisiana 15 80 100 8 of 32Texas 80 45 100 30 of 32

0

50

100

150

200

250

300

0 50 100 150 200 250 300

Estimated Flock Size

Bir

ds

in P

ho

tog

rap

hs R2=0.9761

N=87

Detection Rate : Flock Size Estimates

Mean Estimate/Count=0.91(SE = 0.002)

Detection Rates: FlocksDetection Rates: Flocks

Air Ground< 50 11 15 0.73≥ 50 20 20 1

Flock size Number of flocks Detection rate

Numbers of Birds Recorded By State

Ground surveys

Photo-graphed

Visual estimate

Prop. covered

Number of birds

Prop. covered

Number of birds

NJ 595 0 353 1.0 0 1.0 0 948DE 0 0 0 1.0 0 1.0 0 0VA 1,701 0 0 1.0 0 0.4 0 1,701NC 402 38 82 0.7 53 0.3 0 575SC 3,704 37 5 1.0 32 0.3 0 3,778GA 80 747 128 0.9 26 0.3 0 981FL 3 966 883 1.0 0 0.3 0 1,852AL 0 14 22 1.0 2 0.3 0 38MS 0 4 4 1.0 4 0.3 0 12LA 0 63 56 0.8 0 0.2 0 119TX 0 0 317 0.5 0 0.3 0 317All 6,485 1,869 1,850 0.8 117 0.3 0 10,321

State

Total Number

Recorded

Salt MarshesBarrier BeachesHigh Quality Habitat

Estimate SEGround, Photo 8,354 0Aerial Est. 2,460 148Barrier Beach 157 35Total 10,971 152

Population Estimate forEastern American Oystercatchers

Final Population Estimate = 10,971 ± 298

0

10

20

30

40

50

60

70

80

Per

cen

t

Birds

Habitat

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 Ground count crews: Barry Truitt, Alex

Wilke, Felicia Sanders, Nancy Douglas, Wilke, Felicia Sanders, Nancy Douglas, David Allen, Amanda Dey, David David Allen, Amanda Dey, David MizrahiMizrahi

Acknowledgments, cont’dNew Jersey Division of Fish and WildlifeVirginia Department of Game and Inland FisheriesNorth CarolinaSouth Carolina Department of Natural ResourcesGeorgia Department of Natural ResourcesFlorida Fish and Wildlife CommissionAlabama Wildlife and Freshwater Fisheries DivisionTexas Parks and WildlifeThe Nature ConservancyNational Audubon SocietyNew Jersey Audubon SocietyAudubon North CarolinaAudubon of FloridaHouston Audubon SocietyCape Romain National Wildlife RefugeGrand Bay National Estuarine Research Reserve