Breeding biology of american crows

AsTItAcr.-The breeding biology of cooperatively breeding American Crows (Corvus brachyrhynchos) was studied on Cape Cod, Massachusetts, from 1983-1987. The study site consisted of habitats ranging from a remote barrier beach to populated suburban areas. Family groups ranged in size from two to 10 members, the latter including an adult pair with their oneto four-year-old offspring. Territories were defended year-round and the mean territory size was 42.1 ha. The mean distance between nests of bordering territories was 0.86 km. Most (88%) nests were built in pitch pine (Pinus rigida) trees. Mean nest depth was 24.1 cm, mean total diameter of the nests was 40.7 cm, and the mean diameter of the nest cups was 23.8 cm. Nest height averaged 9.7 m; mean tree height was 10.9 m. Incubation occurred between March and June over an average of 22.3 days. The mean number of days until fledging was 30.1. Reproductive success was measured through the mean number of surviving fledglings. The total mean was 2.0 (N = 46). There was a trend towards increased fledgling production in family groups with six or more members (N = 10, X = 2.6 ? 1.7). Received 16 Oct. 1989, accepted 30 Jan. 1990.