Analysis of 684 pellets from a winter roost of ravens (Corvus corax) at Umiat, Alaska, indicated that during the winters of 1966 and 1967 ravens obtained half of their energy income through predation and half through scavenging. Microtine rodents provided the bulk of the predatory half of the raven's diet, whereas carcasses of caribou (Rangifer arcticus) and ptarmigan (Lagopus spp.) were the items most often scavenged. The relative abundance of prey species in pellets suggests that ravens spent most of their time hunting in upland habitats on the tundra