Snowy Owl Predation on Short-eared Owls

A problem confronting Snowy Owls (Nyctea scandiaca) in their southern incursions is the shortage of food. This difficulty is raised by the presence of other raptors that feed on small mammals. This note shows how little food is found by migrant Snowy Owls and indicates a complex temporary ecological solution. At Tatoosh Island, Washington (48”24’ N, 124” 44’ W) on 25 November 1973, we observed a Snowy Owl near a cache of three dead Short-eared Owls ( Asio fhzmmeus). The latter anneared to have been killed and partially consumed. -Their dorsal feathers had been ruffled, there were small wounds in the head, the pectoral musculature of two individuals had been eaten, and three of the six eyes devoured. We first saw the Snowy Owl when it was perched within 20 m of its alleged prey midden, during a time of severe food shortage for these large owls. In all, five Snowy Owls inhabited this small (6.5-ha) island. Of these, one was subsequently found dead, one was hand-caught by U.S. Coast Guard personnel, and the remaining three disappeared within 10 days. Total residence time of the owls on the island was less than three weeks, a further indication that this was unsuitable long-term habitat. The owls presumably left for the mainland, a distance of less than one mile. The island vegetation consisted almost entirely of thicket, primarily salal (Gaultheriu shuZlon) and salmonberry (Rubus spectabilis). There were only seven