Scavenger Interactions in a Human-Influenced Environment: The Foraging Behavior of the Red-Shouldered Hawk (Buteo lineatus) at Residential Compost Piles

Residential composting has increased in popularity in recent years, along with the untested claim that the addition of animal-based kitchen scraps will increase the number of scavenging wildlife visitors. This study represents the first experimental test of that claim. Using three compost piles consisting respectively of no kitchen scraps (CON), a mix of animal and vegetable scraps (MIX), or only vegetable scraps (VEG) that were monitored with heat-in-motion sensitive cameras, we studied the visitation pattern of attracted wildlife. Of the 29 species identified thus far at the compost piles, I chose to focus on the red-shouldered hawk (Buteo lineatus), the most common raptor species, and the American crow (Corvus brachyrhynchos), by far the most common diurnal species. The red-shouldered hawk had a preference for the MIX pile, which was consistent with the overall trend of increased visitation to the MIX pile by all wildlife visitors, and frequented the piles more often in the winter/spring season. These two avian scavengers showed a distinct association at the compost piles, which appears to be due to the red-shouldered hawk attraction by American crows, perhaps to enhance their foraging. In addition, I noted a novel behavior of the strictly carnivorous red-shouldered hawk: ingestion of vegetable matter at the VEG pile. As a possible explanation of this aberrant behavior, I investigated the presence of small mammals at the compost piles and a nearby location to determine whether the red-shouldered hawk was attracted to the VEG pile primarily because of these prey and not to forage on the vegetable material itself. I found that small mammal activity was significantly higher at the non-pile location. This finding, coupled with related observations, suggested that small mammals were not likely to be the primary cause of red-shouldered hawk foraging at the VEG pile