Territorial behavior of the female brown-headed cow bird (Molothrus ater)

Abstract

The territorial behavior of the female brown-headed cowbird (Molothrus ater) was studied at London, Ontario, in 1966 and 1967. The cowbirds arrived in the study area during the last week of March and the first 2 weeks of April. Adult birds arrived about 2 weeks before the yearlings. Forty-six resident and 56 nonresident females were observed in the study area; these nonresidents appeared to use the area for feeding. The breeding residents established home ranges mainly through the use of threat displays. The defence of these home ranges suggest that they might be classified as territories. Thirty-nine breeding resident females, 17 yearlings, and 22 adults had home ranges ranging from 0.9 to 13.4 ha (average 4.5 ± 0.4 ha).