Effects of Winter Feeding on Limpets by Black Oystercatchers, Haematopus Bachmani

Abstract

Black Oystercatchers fed on limpets in an intertidal boulder field at a rate of 2 limpets°m—2°yr—1. The birds exert a major influence on the microdistribution of these molluscs. Where accessible to oystercatcher predation, limpets are unlikely to survive over a winter once they reach moderate size (10—14 mm). Collisella pelta are exceptional in having refuge in large size. Oystercatchers thus produce and reinforce patchy limpet distributions. Adaptations of the limpets include crypsis and habitat selection of setting larvae. Spatial heterogeneity on local, regional, and broader geographic scales complicates these effects, especially since settlement behavior is constrained from making distinctions between all levels of heterogeneity, e.g., between cliffs where limpets will be relatively safe and boulders where they are at high risk. Locally the effects of bird predation are most notable for Notoacmea persona, but N. scutum, C. digitalis, and C. pelta are also consumed in significant numbers. The resulting microdistribution of limpets affects algal cover, which tends to be effectively removed by their grazing on steep and vertical walls, but which can maintain itself on large horizontal and gently sloping surfaces. Feeding in this locale was confined to the birds' nonbreeding season, fall and winter. By its end the limpets were reduced in number and the birds foraged elsewhere and on other prey. Limpet recruitment may be insufficient to allow year—round feeding in such areas by these birds, whose foraging may represent an adaptive seasonal adjustment to local conditions.

Maritime mammals: terrestrial mammals as consumers in marine intertidal communities

“…We note that predators need not necessarily be abundant to affect an impact on prey distribution and abundance, as Frank (1982) has demonstrated relative to oystercatcher predation on intertidal limpets, and as Estes et al (1998) have shown relative to killer whale predation on sea otters. Wooton (1992) has suggested that raccoons preying on sea urchins (Strongylocentrotus spp.)…”

Introduced rats indirectly change marine rocky intertidal communities from algae- to invertebrate-dominated

“…Herbivorous snails and limpets are important components of gull and oystercatcher diets (20,21,25,27), and both are known to significantly reduce fleshy algal cover in the marine rocky intertidal through grazing (21,(27)(28)(29)(30)(31). Therefore, rat predation on the birds indirectly changes the rocky intertidal community from an algal-to an invertebrate-dominated system by releasing intertidal herbivores from predation pressure, which reduces fleshy algal cover via increased herbivory.…”

“…Gulls and oystercatchers are groundnesting, year-round residents of the Aleutian Islands, with gulls occurring throughout the archipelago and oystercatchers occurring east of Ϸ176°E (20). They forage extensively in the intertidal, significantly decreasing densities of intertidal invertebrates through predation and indirectly influencing the presence of fleshy algae (21)(22)(23)(24). In the summer, oystercatchers establish combined nesting and feeding territories, thereby foraging in the intertidal near their nesting sites (20), whereas gulls feed almost exclusively in the intertidal starting in mid-July after their young begin to fledge (25).…”

Variation in owl limpetLottia giganteapopulation structures, growth rates, and gonadal production on southern California rocky shores

“…Also, owl limpets can be strongly preyed upon by the American black oystercatcher Haematopus bachmani, a territorial shorebird that can exert sufficient predation pressure to influence limpet abundances and L. gigantea's utilization of microhabitat (Lindberg et al 1987(Lindberg et al , 1998. However, American black oystercatchers are very sensitive to human presence (Sowls et al 1980, Frank 1982, Lindberg et al 1987, 1998 and are essentially absent from heavily populated, urban coastlines.…”