A global assessment of the conservation status of the American Oystercatcher Haematopus palliatus
62 – 82
26 August 14
Robert J. Clay, Arne J. Lesterhuis, Shiloh Schulte, Stephen Brown, Debra Reynolds, Theodore R. Simons
BirdLife International, Gaetano Martino 215 esq. Teniente Ross, Asunción, Paraguay
The American Oystercatcher Haematopus palliatus is the most widely distributed of the four oystercatcher species in the Western Hemisphere. Its range covers almost the entire Atlantic Coast from northeastern United States to southern Argentina; on the Pacific Coast it is found from northern Mexico to central Chile. This assessment covers the entire range of the species, and is not intended to serve as a substitute or update for conservation plans that cover the U.S. Atlantic and Gulf Coast populations. Readers are advised to refer to those plans, available at www.whsrn.org, for more detailed information about U.S. populations.
The subspecific taxonomy of H. palliatus is far from clear, but five races are recognized in this assessment, primarily to facilitate reference to specific populations (Fig. 1). These are nominate H. p. palliatus (coasts of eastern and southern United States; eastern Mexico; Pacific and Caribbean coasts of Central America; the Caribbean; and northern and eastern South America); H. p. frazari (Gulf of California and western Mexico); H. p. pitanay (coast of western South America); H. p. durnfordi (coast of southeast South America) and H. p. galapagensis (Galapagos Islands). The Galapagos race may deserve species status.
Based on a review of existing population estimates and an extrapolation of data from quantitative surveys throughout its range, revised estimates are given for the populations of all five subspecies, and a total population of about 43,000 individuals. The nominate race is the most abundant with an estimated population size of about 20,000 individuals, while the least abundant is H. p. galapagensis, with just 300 individuals estimated. Biogeographic population estimates were used to determine 1% threshold levels and identify sites of regional and global conservation importance. A total of 20 sites have been identified for H. p. palliatus, 5 for H. p. frazari, 10 for H. p. pitanay and 10 for H. p. durnfordi. No key sites were identified for H. p. galapagensis as it is found in low density scattered throughout the islands. Of these 45 sites, 14 have counts that surpass the 1% level of the global population, and are thus of global conservation significance for the species. Because the species is a dispersed breeder, the 1% threshold is of limited value in identifying key breeding sites. For the time being, these have been defined as sites holding 20 or more breeding pairs; 17 such sites have been identified, with all but four in the United States. It is hoped that a more rigorous approach for identifying key breeding sites can be developed in the future.
As an obligate coastal species, American Oystercatcher is at risk from widespread habitat loss due to coastal development, and recreational activities that lead to nest disturbance and increased predation. This is exacerbated by the species’ low population size and low reproductive success. Climate change also poses a significant future threat, especially with regard to sea-level rise.
To address these threats, conservation actions are proposed that focus on increased legal protection for the species and on the conservation of key sites and important habitats. Conservation could include implementing beneficial management practices, such as restoration of nest and roost sites, controlling predation, and reducing disturbance. Education and outreach programs are needed throughout the species’ range, especially for beach users and urban planners. Training programs will be necessary to ensure successful implementation of many of the priority conservation actions. Finally, a key first step in conserving this species across its range is the creation of a H. palliatus Working Group. Modelled after the U.S. American Oystercatcher Working Group this organization could unite researchers, conservationists, and educators from across the hemisphere to foster coordinated research, conservation action, and monitoring as outlined in this assessment.