Fluctuations in the Number of Northern Harriers (Circus cyaneus hudsonius) at Communal Roosts in South Central Ohio
Eleven Northern Harrier (Circus cyaneus) roosts were studied in south central Ohio during the four winters of 1973-1974 through 1976-1977. They ranged from 8 to 59 birds. The number of birds using each roost fluctuated throughout the winter. While the abandonment of at least three roosts in midwinter can be attributed to severe weather, reciprocal fluctuations in the number of birds at nearby roosts and the direction of birds returning to one roost suggest that Northern Harriers will shift roost sites locally in an effort to maintain proximity to their hunting areas.