Code

CCBTR-04-09

Publication Date

2004

Abstract

Biologists along the east coast of the United States have recently expressed concern about the conservation status of the American Oystercatcher (Haematopus palliatus). The species has a relatively small population size and depends on coastal habitat that is under pressure from humans for development and recreation. Several studies of American Oystercatcher productivity have suggested that the species is inherently intolerant to human disturbance and experiences low productivity rates in areas where their breeding habitat is also used for human recreation. As a beach-nesting bird, their nesting attempts are also very vulnerable to destruction by mammalian and avian predators, which have been known to experience population increases because of human influenced factors. The undeveloped barrier islands and marshes of Virginia’s Eastern Shore support over 500 pairs of breeding American Oystercatchers and provide a unique opportunity to study their productivity in the relative absence of disturbance from direct human activity. Some of the islands are, however, inhabited by high numbers of common raccoons (Procyon lotor). The Nature Conservancy’s Virginia Coast Reserve (TNC), in cooperation with The Center for Conservation Biology at The College of William and Mary (CCB) and other partners, currently supports several efforts aimed at investigating the population status and breeding and wintering ecology of the species. These efforts include annual studies of oystercatcher productivity on the barrier islands and in the lagoon system, annual surveys of breeding and wintering populations and a banding program for oystercatcher adults and chicks. The primary objective of productivity monitoring has been to compare productivity in habitats managed for mammalian predators and those that are not in order to assess the effectiveness of the predator removal as a management strategy for increasing the reproductive success of beach nesting shorebirds and waterbirds. The annual breeding and wintering surveys provide consistent and precise counts of oystercatchers along the Virginia coast so that managers can track changes in population numbers and distribution. Finally, the banding program will increase the number of color-banded birds in the population so that researchers may examine questions concerning migration and dispersal, survival rates and habitat use. One hundred and fifty-three pairs of American Oystercatchers were monitored for productivity during the 2004 breeding season. Eighty-one nested on Metompkin Island, which is managed by TNC for mammalian predators. Twenty-five nested on Wreck Island Natural Area Preserve, which is not managed for mammalian predators but did not have any predator activity during the 2004 breeding season. Fortyseven nested in the marshes of the lagoon system located adjacent to Wachapreague, Virginia. American Oystercatchers experienced high productivity on Metompkin Island and Wreck Island (0.79-1.18 young fledged per pair) for the third and second consecutive years, respectively. These productivity levels continue to be well above what is typically recorded for this species in other parts of its range, and our results suggest that the absence of mammalian predators on these islands allows for the higher productivity of pairs nesting there. American Oystercatchers breeding in the marshes off of Wachapreague also experienced high productivity in 2004 – 0.85 young fledged per pair. Productivity of oystercatchers in this habitat is very vulnerable to flooding events and appears to be highly variable from year to year depending on the timing of egg-laying, spring tide events, storms and storm influenced tide events. A total of 706 adult American Oystercatchers (327 pairs and 52 single adults) were recorded during the 2004 Piping Plover, Wilson’s Plover and American Oystercatcher survey, a 26.1% increase from 2000 when oystercatchers were first systematically surveyed along the coast of Virginia. Breeding pairs were documented on every barrier island along the Eastern Shore of Virginia except for Walllops Island. Only seven pairs were documented west and south of the Chesapeake Bay. Sixty-two American Oystercatcher chicks and two adults were banded during the 2004 breeding season. At least fifty-seven of the chicks fledged. We will continue to work with other states to further develop Virginia’s banding program, upon which researchers, managers and students can build in the future.

Species

American Oystercatcher

Source

Center for Conservation Biology Technical Report Series. College of William and Mary, Williamsburg, VA.

Pages

26

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