Black Oystercatcher (Haematopus bachmani) 



World Breeding Range 



Black Oystercatchers are shorebirds of the 

 outer coast of the northwest Pacific. Adults 

 establish breeding territories on mainland rocky 

 beaches and offshore rocks and islands. An 

 oystercatcher nest, composed of a scrape lined 

 with pebbles and shell fragments, is surprisingly 

 difficult to find. One to three cryptically colored 

 eggs are placed directly on the pebbles. 



Black Oystercatcher young are precocial and 

 may leave the nest within hours of hatching. 

 Although they remain near the nest at first, 

 within a few days chicks follow adults to intertidal 

 foraging areas. The California mussel (Mytilus 

 califomianus) is the chief food of oystercatchers 

 in the Channel Islands (Hunt et al. 1979) as well 

 as in northern California (Helbing 1977), and 

 limpets and chitons make up most of the remainder 

 of the diet. Chicks at the nest are frequently fed 

 crabs (Hartwick 1976, Helbing 1977). 



Mortality among eggs and chicks is apparently 

 high. Hartwick (1974) lists gull predation as an 

 important cause of mortality. In addition, chicks 

 and eggs are frequently washed "overboard" from 

 nests by storm waves. 



During the winter, oystercatchers are 

 gregarious (Webster 1941) and can be observed 

 feeding along rocky portions of the California 

 coast. With their bright orange bills, pink feet, 

 and loud distinctive call, these birds are con- 

 spicuous. 



CALIFORNIA POPULATION 



Black Oystercatchers are a non-colonial 

 nesting species, although they are usually found 

 on the same offshore islands and rocks as colonial 

 nesting seabirds. They establish large nesting and 

 feeding territories and thus distribute themselves 

 along the available coastal habitat. Actual nests 

 were pinpointed only for a small percentage of 

 the sites listed in this catalog. Nesting was 

 indicated more often from the territorial defense 

 behavior of adults. This method obviously has 

 limitations since approach to a nest must be close 

 enough to initiate a reaction from the adults. For 

 this reason the catalog total for this species is 

 almost certainly low. The actual breeding popu- 

 lation size is probably about 1 ,000 birds. 



Information presented in this catalog 

 gives a good representation of the overall breeding 

 pattern of this species, a population of single 

 nesting pairs widely dispersed along the entire 

 California coastline. Concentrations of 242 Black 

 Oystercatchers in the Channel Islands and 40 

 breeding birds in the Farallon Islands (429 012) 

 represent nearly half of the catalog breeding 

 total. 



HISTORICAL STATUS & VULNERABILITY 



Black Oystercatchers disappeared from the 



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