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