Theodore R. Simons
Shiloh A. Schulte
2015
<p>We used an information-theoretic approach to assess the factors affecting the reproductive success of American Oystercatchers Haematopus <br />palliatus on the Outer Banks of North Carolina. We evaluated survival with respect to nesting island, year, time of season, brood age, distance <br />to tide (m), presence of off-road vehicles and proximity of foraging habitat. The daily nest survival (mean 0.981, standard error [SE] 0.002) <br />was affected by year and island, and declined over the nesting season. Mammals were responsible for 54% of identified nest failures. Daily <br />brood survival (mean 0.981, SE 0.002) varied by island and increased non-linearly with age, with highest mortality in the seven days after <br />hatching. Model results indicate direct access to foraging sites has a positive effect on brood survival, whereas presence of off-road vehicles <br />has a negative effect. We studied chick behavior and survival using radio telemetry and direct observation and found that vehicles caused <br />mortality and affected behavior and resource use by oystercatcher chicks. We identified the source of mortality for 37 radio-tagged chicks. <br />Six (16%) were killed by vehicles, 21 (57%) by predators, and 10 (27%) by exposure and starvation. From 1995 to 2008, 25 additional <br />oystercatcher chicks were found dead, 13 (52%) killed by vehicles. Chicks on beaches closed to vehicles used beach and intertidal zones <br />more frequently than chicks on beaches open to vehicles. Chick predators included Great Horned Owls Bubo virginianus, Fish Crows <br />Corvus ossifragus, cats Felis catus, mink Mustela vison, raccoons Procyon lotor, and ghost crabs Ocypode albicans. The factors affecting <br />reproductive success differed between the incubation and chick-rearing stages. Management actions that influence chick survival will have a larger effect on total productivity than actions affecting nest survival.</p>
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Pacific Seabird Group
Factors affecting the reproductive success of American Oystercatchers <i>Haematopus palliatus</i> on the outer banks of North Carolina
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