Global climate change is rapidly changing the world’s environment and is predicted to accelerate current rates of sea level rise, eventually inundating coastal areas. These changes will have an outstanding impact on organisms that rely on coastal areas and intertidal zones, especially shorebirds. One species that is susceptible to the effects of climate change on the U.S. Atlantic Coast is the American Oystercatcher (Haematopus palliatus). Future evaluations of the relative impact of climate change on shorebird populations require a comprehensive understanding of current population dynamics. We designed a stochastic population model to explore the dynamics of a local population of oystercatchers and identify the demographic parameters driving observed population trends in Massachusetts. From 2005 – 2008, we collected nesting data and conducted a mark-recapture study to parameterize this model for American Oystercatchers in Nantucket, Massachusetts.
Results/Conclusions
Fecundity (0.20, SE 0.03 females fledged per female) was higher than those from other Atlantic Coast populations. Furthermore, we found that egg survival was exceptionally high but chick survival was low. We used advanced mark-recapture techniques to estimate annual adult survival and breeding-site fidelity for American Oystercatchers. Our results revealed a high rate of true annual survival (0.94, SE 0.03) and a strong, but variable, degree of breeding-site fidelity (0.93, SE 0.05). Additionally, we used mark-recapture data to estimate juvenile annual survival (0.51) and subadult transition probability (0.17). Our model shows that current reproductive success is sufficient to maintain the population (λ = 0.97, 95% CI: 0.90 - 1.02), but not sufficient to predict an observed recent increase. Using reverse encounter histories, we estimated movement parameters and found approximately 7% of the population permanently emigrates while 16% of the population is likely comprised of adults immigrating into Nantucket. Demographic analyses confirmed that high immigration rates, likely related to warming climate, are responsible for the observed growth (λ = 1.08, 95% CI: 0.99 - 1.16). These modeling efforts provide a foundation for continued examination of shorebird population demographics and the evaluation of the likely influence of sea level rise (again the result of warming climate), on local populations. Furthermore, the continued monitoring of oystercatcher demographics may provide a measure of intertidal community health in the face of sea level rise. Future warming will likely lead to the continued increase of American oystercatchers, and possible decline of Black oystercatchers in the Pacific.
