Techniques for differentiating pellets of short-eared owls and Northern Harriers

Short-eared Owls (Asioflammeus) and Northern Harriers (Circus cyaneus) are sympatric throughout much of their ranges. In Massachusetts these species usually co-exist temporally, may have overlapping territories, and are both dependent on meadow voles (Micro&s pennsylvanicus) for food (Holt and Melvin, in press). Because of similarities in appearance and content, pellets of the two species are often difficult to separate. In this note we describe techniques for differentiating pellets of the Short-eared Owl and Northern Harrier.