DOI 10.1007/s00442-007-0947-0BEHAVIORAL ECOLOGY- ORIGINAL PAPER Movements of wintering surf scoters: predator responses to diVerent prey landscapes

Abstract The distribution of predators is widely recog-nized to be intimately linked to the distribution of their prey. Foraging theory suggests that predators will modify their behaviors, including movements, to optimize net energy intake when faced with variation in prey attributes or abundance. While many studies have documented changes in movement patterns of animals in response to temporal changes in food, very few have contrasted move-ments of a single predator species naturally occurring in dramatically diVerent prey landscapes. We documented variation in the winter movements, foraging range size, site Wdelity, and distribution patterns of a molluscivorous sea duck, the surf scoter (Melanitta perspicillata), in two areas of coastal British Columbia with very diVerent shellWsh prey features. Baynes Sound has extensive tidal Xats with abundant clams, which are high-quality and temporally stable prey for scoters. Malaspina Inlet is a rocky fjord-like inlet where scoters consume mussels that are superabun-dant and easily accessible in some patches but are heavily depleted over the course of winter. We used radio telemetry to track surf scoter movements in both areas and found that in the clam habitats of Baynes Sound, surf scoters exhibited limited movement, small winter ranges, strong foraging site Wdelity, and very consistent distribution patterns. By con-trast, in mussel habitats in the Malaspina Inlet, surf scoters displayed more movement, larger ranges, little Wdelity to speciWc foraging sites, and more variable distribution pat-terns. We conclude that features associated with the diVer-ent prey types, particularly the higher depletion rates of mussels, strongly inXuenced seasonal space use patterns. These Wndings are consistent with foraging theory and con-Wrm that predator behavior, speciWcally movements, is environmentally mediated