A Demographic Model for American Oystercatchers in North Carolina Shiloh Schulte and Ted Simons USGS Cooperative Fish and Wildlife Research Unit, Department of Zoology, North Carolina State University, Raleigh, NC

Conservation Status  ~11,000 oystercatchers in the United States.  ~675 breeding adults in North Carolina  Threatened in Georgia, and a species of concern in Florida and Alabama  Threats: coastal development, recreational activity, increasing predator populations, pollution and destruction of food resources, and sea level rise.

Assessment  Surveys and monitoring programs: – Valuable, but usually limited in scope  Demographic modeling –Combines vital rate estimates –Greater insight into population dynamics –Predictive –Determines which life stages have the most influence on population growth

Modeling Objectives  1) Quantify risks to the oystercatcher population in North Carolina  2) Determine the effect of hurricanes on population trajectory  2) Identify the most critical data needs  3) Identify life stages where management actions might be most effective

Study sites on the Outer Banks of North Carolina Cape Hatteras National Seashore Cape Lookout National Seashore

Field Methods  Monitored 1129 nesting attempts over 10 years on the Outer Banks of NC  Individually banded over 280 oystercatchers from 1999 – 2006  Annual resight surveys to document adult survival and recruitment of subadults into the breeding population

Model Construction

Parameter Estimates and Data Sources  Adult survival: 0.93 (SE 0.013) - Mark-resight study  Fecundity: (SE 0.011) – Nest/chick monitoring  Subadult survival with transition: 0.15 (SE 0.1) – Ens et al. 1995, Safriel et al  Subadult survival without transition: 0.75 (SE 0.1) – Ens et al. 1995, Safriel et al  Juvenile survival: 0.7 (SE 0.1) - Goss-Custard et al. 1982, Kersten and Brenninkmeijer 1995

Model Output  Stable stage distribution, lambda, and matrix element sensitivities  Added stochasticity based on standard errors of parameter estimates  Calculated the population growth rate and the probability of a 50% decline over 50 years based on 1000 model runs

Population Trajectory: Baseline Model Years Population

Results: Baseline Model  Lambda:  Probability of 50% decline over 50 years:  Sensitivities:

Hurricane Effects  Improved habitat and decreased predators  After Hurricane Isabel, overall nest survival jumped to (SE 0.104, n=92). Hurricane Isabel

Population Trajectory: Hurricane Models Years Population 0 Baseline: λ = Year Hurricane: λ = Year Hurricane: λ =

Conclusions  The oystercatcher population in North Carolina is not self-sustaining  Bonanza effects from hurricanes may mitigate population decline, but are unlikely to reverse the trend  Management actions for maximum effect: –Decrease risks to adults, especially during winter (disturbance, loss of food resources, catastrophic events, oil spills, etc) –Increase baseline reproductive success  Good estimates of Juvenile and Subadult survival and dispersal are still needed

Dissertation Committee Dr. Ted Simons Dr. Ken Pollock Dr. Jim Gilliam Dr. Jaime Collazo Previous AMOY grad students at NCSU Melissa Davis Conor McGowan

Questions?

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