The black oystercatcher is a keystone species along the North Pacific shoreline and is believed to be a particularly sensitive indicator of the overall health of the rocky intertidal community.  Annual surveys have been conducted along the Oregon Coast since 2005. 

Description

The black oystercatcher is a large, long-lived shorebird about 38 centimeters (15 inches) in length with a long, thick, reddish-orange bill, a yellow eye encircled by an orange ring, and pink legs, all of which are strikingly set off by entirely black plumage.  Juveniles have somewhat browner plumage and a dark tip on the bill.  Oystercatchers are monogamous, returning to the same nesting territories to pair with the same mate each year.  

Distribution

Black oystercatchers occur along the North American Pacific coast from the Aleutian Islands to Baja California, and are most abundant in the northern portions of their range, from Alaska to southern British Columbia.  Breeding oystercatchers are highly territorial and nesting densities are low; however, the birds tend to gather in groups of tens to hundreds during the winter months.

Population Status

The world population of black oystercatchers is estimated at 10,000.  In Oregon, the estimated population, based on seabird survey information from the late 1980s is 350.  Approximately 250 individuals have been found annually during land-based surveys along the Oregon Coast between 2005 and 2007.  This number does not include black oystercatchers on offshore rocks and islands too distant to survey from the mainland.  The black oystercatcher is a U.S. Fish and Wildlife Service “Species of Concern” because of its small population size, restricted range, and threats to habitat from human and natural factors that may potentially limit its long-term viability.

Habitat and Diet

Oystercatchers inhabit marine shorelines, favoring rocky shorelines.  They make their nests above the high tide line on offshore rocks, rocky shores, and sand/gravel beaches. The typical nest bowl is a small depression in the sediment containing rock flakes, pebbles, and shell fragments.  Foraging habitat is primarily low-sloping gravel or rock beaches where prey is abundant.  Oystercatchers feed on a variety of intertidal invertebrates including mussels, limpets, chitons, crabs, barnacles and other small creatures.  Contrary to what their name implies, they do not feed on oysters.

Reasons for Decline

Black oystercatchers are highly vulnerable to natural and human disturbances. Major threats include predation of eggs and young by native and non-native predators; coastal development; human disturbance (e.g., induced nest abandonment, nest trampling); vessel wakes, especially when they coincide with high tides; shoreline contamination such as oil spills (resulting in both direct mortality and indirect effects such as reduction in food availability or quality); and global climate change, with its resultant effects on feeding and/or nesting resources.  Information is lacking on contaminant and pollutant levels locally, and how these might affect fitness, especially in or near highly developed areas within the species’ range. 

Conservation Measures

Currently, conservation efforts for the black oystercatcher are limited by a lack of baseline information for many areas on the following:  the locations and sizes of important breeding populations; local and overall population status and trends; hatching success, fledging success and adult survival; regional threats to survival and productivity; the locations of important wintering concentration areas and the numbers of birds in those areas; movements between breeding and wintering sites; and population structure.

In Oregon, management plans to protect the black oystercatcher are being developed and will likely begin with signage at key nesting sites to prevent disturbance by recreationists.

References

Andres B.A. and G.A. Falxa. 1995. Black Oystercatcher (Haematopus bachmani). In The birds of North America, No. 155 (A. Poole and F. Gill, Eds.). Academy of Natural Sciences. Philadelphia, and American Ornithological Union. Washington D.C.

Brown, S., C. Hickey, and B. Harrington [Eds.]. 2000. United States Shorebird Conservation Plan. Manomet Center for Conservation Sciences. Manomet, MA.

Hodder, J.  Black Oystercatcher pp. 209-210 in Birds of Oregon:  A General Reference.  D.B. Marshall, M.G. Hunter, and A.L. Contreras, Eds.  Oregon State University Press, Corvallis, OR.

Pitman, R. L., J. Hodder, M. R. Graybill, and D. H. Varoujean. 1985. Catalog of Oregon Seabird Colonies. Unpublished Report. U.S. Fish and Wildlife Service. Portland, OR.

Purdy, M.A. and E. H. Miller. 1988. Time budge and parental behavior of breeding America Black Oystercatcher (Haematopus bachmani) in British Columbia. Canadian Journal of Zoology 66:1742-1751.

Tessler, D.F., J.A. Johnson, B.A. Andres, S. Thomas, and R.B. Lanctot.  2007. Black Oystercatcher (Haematopus bachmani) Conservation Action Plan. International Black Oystercatcher Working Group, Alaska Department of Fish and Game, Anchorage, Alaska, U.S. Fish and Wildlife Service, Anchorage, Alaska, and Manomet Center for Conservation Sciences, Manomet, MA. 115 pp.

US Fish and Wildlife Service. Unpublished data from the 1988 Oregon seabird colony survey. U.S. Fish and Wildlife Service, Oregon Coastal Refuges Headquarters, Newport, OR.