(full paper is archived in the Miller Library)
Title: Feeding of the Black Oystercatcher, Haematopus bachmani, Audubon, and its relationship to the distribution of limpets (Gastropoda: Patellacea) on central California rocky shores
Student Author(s): Hahn, Thomas P.
Faculty Advisor(s): Abbott, Donald
Location: Final Papers Biology 175H
Date: June 1982
Keywords: upper intertidal
Abstract: The diet of Black Oystercatchers (Haematopus bachmani Audubon) studied at Pacific Grove, California, included many limpets. In this study, the birds usually took limpets clearly exposed to view, not those hidden beneath larger leafy algae. Limpets on very steep slopes were only attacked if the bird could do so while standing an adjacent gentle slope. Most of the limpets eaten were Collisella pelta and C. digitalis; virtually none were C. scabra living on foraging sites. Evidence is presented indicating that selective predation by oystercatchers is important in the localization of C. pelta under large leafy algae (animals in plain view are selectively preyed upon), and in the separation of the habitat niches of C. scabra and C. digitalis. C. digitalis survives best on steep surfaces inaccessible to foraging oystercatchers; C. scabra, largely not subject to oystercatcher predation, is more abundant on horizontal surfaces where competition from other grazing limpets may be less.