Winter roost sites of Northern Harriers and Short-eared Owls on Illinois grasslands

Characteristics of the diets and roosting habitats used by Northern Harriers ( Cirrus cyaneus) and Short-eared Owls (Asio flammeus) on grassland sanctuaries in Jasper and Marion counties, southeastern Illinois, were described for December 1993 and January 1994.Northern Harrier communal roosts contained from 21-43 individuals and were only observed in undisturbed cool-season grasses. Short-eared Owls also roosted communally (3-17 individuals) but the two species were not observed to roost within the same fields. Short-eared Owls roosted in shorter cover than Northern Harriers, but there was no evidence of selection for any grass or management type by Short-eared Owls. Both species frequently fed on southern beg lemmings (Synaptomys cooperi) and avian remains were found in less than 5% of all pellets.