Population dynamics of the American oystercatcher (Haematopus palliatus) near the northern limit of its range

American Oystercatchers (Haematopus palliatus) expanded their range north along the Atlantic Coast, reaching Massachusetts 40 years ago. Concurrent to northward range expansion, oystercatchers have declined in the core part of their range, and have been designated a "Species of High Concern" by the U.S. Shorebird Plan. I examined the demographics of a migratory population of American Oystercatchers in Nantucket, Massachusetts to explore factors influencing local populations. I estimated fecundity (0.20 females fledged per female), annual survival, and dispersal using a variety of field and statistical techniques. I analyzed data from four nesting seasons for oystercatchers in Nantucket and examined temporal patterns in reproductive success. All my measures of reproduction were higher than those from other Atlantic Coast populations. I hypothesized that island populations experience higher reproductive success due to the absence of mammalian predators, and these populations may be sustaining mainland populations. Furthermore, I found that egg survival was exceptionally high but chick survival was low. Therefore, identification of chick loss should be a priority in conservation efforts. I used advanced mark-recapture techniques to estimate annual adult survival and breeding-site fidelity for American Oystercatchers. My results revealed a high rate of true annual survival (0.94) and a strong, but variable, degree of breeding-site fidelity (0.93). Additionally, I used mark-recapture data to estimate juvenile annual survival (0.51) and subadult transition probability (0.18). Using perturbation analyses, I found adult survival and breeding-site fidelity had the greatest impact on local population growth. My modeling also indicated that current reproductive success is sufficient to maintain the population (lambda = 0.970, 95% CI: 0.90--1.02), but not sufficient to predict the recent increase. Using reverse encounter histories, I 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 are responsible for the observed growth (lambda = 1.08, 95% CI: 0.99--1.16). My dissertation provides a foundation for continued examination of shorebird population demographics, a model for demographic analyses of a species of conservation concern, and a preliminary work illuminating the advantages of dispersal and the relationship between breeding-site fidelity and reproductive success.