A Demographic Model for A Demographic Model for American Oystercatchers in American Oystercatchers in

North CarolinaNorth Carolina

Shiloh Schulte and Ted SimonsShiloh Schulte and Ted SimonsUSGS Cooperative Fish and Wildlife USGS Cooperative Fish and Wildlife

Research Unit, Department of Zoology, North Research Unit, Department of Zoology, North Carolina State University, Raleigh, NCCarolina State University, Raleigh, NC

Conservation StatusConservation Status

~11,000 oystercatchers in the ~11,000 oystercatchers in the United States. United States.

~675 breeding adults in North ~675 breeding adults in North CarolinaCarolina

Threatened in Georgia, and a Threatened in Georgia, and a species of concern in Florida species of concern in Florida and Alabamaand Alabama

Threats: coastal development, Threats: coastal development, recreational activity, increasing recreational activity, increasing predator populations, pollution predator populations, pollution and destruction of food and destruction of food resources, and sea level rise. resources, and sea level rise.

AssessmentAssessment

Surveys and monitoring programs:Surveys and monitoring programs:– Valuable, but usually limited in scopeValuable, but usually limited in scope

Demographic modelingDemographic modeling– Combines vital rate estimates Combines vital rate estimates – Greater insight into population dynamicsGreater insight into population dynamics– PredictivePredictive– Determines which life stages have the most Determines which life stages have the most

influence on population growthinfluence on population growth

Modeling ObjectivesModeling Objectives

1) Quantify risks to the oystercatcher 1) Quantify risks to the oystercatcher population in North Carolinapopulation in North Carolina

2) Determine the effect of hurricanes on 2) Determine the effect of hurricanes on population trajectorypopulation trajectory

2) Identify the most critical data needs2) Identify the most critical data needs 3) Identify life stages where management 3) Identify life stages where management

actions might be most effectiveactions might be most effective

Study sites on the OuterBanks of North Carolina

Cape Hatteras National Seashore

Cape Lookout NationalSeashore

Field MethodsField Methods

Monitored 1129 nesting Monitored 1129 nesting attempts over 10 years on the attempts over 10 years on the Outer Banks of NCOuter Banks of NC

Individually banded over 280 Individually banded over 280 oystercatchers from 1999 – oystercatchers from 1999 – 20062006

Annual resight surveys to Annual resight surveys to document adult survival and document adult survival and recruitment of subadults into recruitment of subadults into the breeding populationthe breeding population

Model ConstructionModel Construction

Parameter Estimates and Data Parameter Estimates and Data SourcesSources

Adult survival: Adult survival: 0.930.93 (SE 0.013) - (SE 0.013) - Mark-resight study Mark-resight study

Fecundity: Fecundity: 0.1040.104 (SE 0.011) (SE 0.011) – Nest/chick monitoring– Nest/chick monitoring

Subadult survival with transition: Subadult survival with transition: 0.150.15 (SE 0.1) (SE 0.1) – – Ens et al. 1995, Safriel et al. 1984Ens et al. 1995, Safriel et al. 1984

Subadult survival without transition: Subadult survival without transition: 0.750.75 (SE 0.1) (SE 0.1) – Ens et al. 1995, Safriel et al. 1984– Ens et al. 1995, Safriel et al. 1984

Juvenile survival: Juvenile survival: 0.70.7 (SE 0.1) (SE 0.1) - Goss-Custard et al. - Goss-Custard et al.

1982, Kersten and Brenninkmeijer 19951982, Kersten and Brenninkmeijer 1995

Model OutputModel Output

Stable stage distribution, lambda, and matrix Stable stage distribution, lambda, and matrix element sensitivitieselement sensitivities

Added stochasticity based on standard Added stochasticity based on standard errors of parameter estimateserrors of parameter estimates

Calculated the population growth rate and Calculated the population growth rate and the probability of a 50% decline over 50 the probability of a 50% decline over 50 years based on 1000 model runsyears based on 1000 model runs

Population Trajectory: Baseline ModelPopulation Trajectory: Baseline Model

1000

800

600

400 0 50

Years

Po

pu

lati

on

Results: Baseline ModelResults: Baseline Model

Lambda: Lambda: 0.97280.9728 Probability of 50% Probability of 50%

decline over 50 years: decline over 50 years: 0.9040.904

Sensitivities: Sensitivities:

0

0.2

0.4

0.6

0.8

1

Sa F Sst Ss Sj

Hurricane EffectsHurricane Effects

Improved habitat and decreased predatorsImproved habitat and decreased predators After Hurricane Isabel, overall nest survival jumped After Hurricane Isabel, overall nest survival jumped

to 0.501 (SE 0.104, n=92). to 0.501 (SE 0.104, n=92).

0

0.1

0.2

0.3

0.4

0.5

0.6

1997 1998 1999 2000 2001 2002 2003 2004 2005

Ne

st

su

rviv

al Hurricane Isabel

Population Trajectory: Hurricane ModelsPopulation Trajectory: Hurricane Models

1000

400

800

200

600

0 50 Years

Po

pu

lati

on

0

Baseline:λ = 0.9728

15 Year Hurricane: λ = 0.9890

10 Year Hurricane:λ = 0.9983

ConclusionsConclusions The oystercatcher population in North Carolina is The oystercatcher population in North Carolina is

not self-sustainingnot self-sustaining Bonanza effects from hurricanes may mitigate Bonanza effects from hurricanes may mitigate

population decline, but are unlikely to reverse the population decline, but are unlikely to reverse the trendtrend

Management actions for maximum effect:Management actions for maximum effect:– Decrease risks to adults, especially during winter Decrease risks to adults, especially during winter

(disturbance, loss of food resources, catastrophic (disturbance, loss of food resources, catastrophic events, oil spills, etc) events, oil spills, etc)

– Increase baseline reproductive successIncrease baseline reproductive success Good estimates of Juvenile and Subadult survival Good estimates of Juvenile and Subadult survival

and dispersal are still neededand dispersal are still needed

Dissertation CommitteeDissertation CommitteeDr. Ted SimonsDr. Ted SimonsDr. Ken PollockDr. Ken PollockDr. Jim GilliamDr. Jim GilliamDr. Jaime CollazoDr. Jaime Collazo

Previous AMOY grad Previous AMOY grad students at NCSUstudents at NCSUMelissa DavisMelissa DavisConor McGowanConor McGowan

Questions?Questions?

http://www.ncsu.edu/project/grsmgis/AMOY/Research.htmhttp://www.ncsu.edu/project/grsmgis/AMOY/Research.htm