A demographic description of the co-operatively breeding American Crow Corvus brachyrhynchos. In: Adams, N. J. & R. H. Slotow, (eds) Proceedings of the 22nd International Ornithological Congress, Durban, South Africa, 16-22 August 1998. Ostrich 69 (3&4): 328.
Kevin J. McGowan
.Ecology & Systematics, Cornell University, Ithaca, New York, 14853-2701, USA
The American Crow is the only member of the genus Corvus known to be a regular cooperative breeder. Although it is a widespread and common bird in North America, little quantified information is available on any aspect of its life history. I studied a population of American Crows in New York state from 1988 to 1997, individually marking over 650 crows. I collected data on reproductive success, movements, and survival. Breeding pairs of crows held permanent territories, but often left them to forage and roost. Auxiliaries were present at 79% of nests; group size ranged up to 15. Most extra crows were helping their parents. Auxiliaries had no apparent effect on nesting success. Survival of young over the first year of life was high (48%), as was breeder survival (93% per year). Most crows did not achieve breeding status until 2 to 6+ years of age. Inheritance of at least part of the natal territory was an important avenue to breeding for males; females usually found breeding spots farther away. Territory ownership in American Crows may place constraints on the life history of the species that lead to cooperative breeding, despite the fact that they do not hold all-purpose territories.
Key words: reproduction, territory, demography, helping, survival