Date of this Version
Red-winged Blackbirds (Agelaius phoeniceus), Brown-headed Cowbirds (Molothrus ater), and Starlings (Sturnus vulgaris) are ubiquitous breeding birds in much of North America. The Common Grackle (Quiscalus quiscula) is an abundant breeding bird east of the Rocky Mountains (Dolbeer and Stehn 1979). Although these species are widely dispersed and generally unassociated during the nesting season, they often associated closely in winter roosts containing up to 10 million birds in the southern United States (Meanley and Webb 1965, Meanley 1971). Little is known about the comparative migration patterns of the four species and the resulting mixture of local breeding populations in winter. Comparative analyses within and among these species provide the opportunity for testing hypotheses about migration. Furthermore, a better understanding of blackbird (Icteridae) and Starling migration is of practical importance because of increased conflicts between these species and humans, especially at winter roost sites (Graham 1978).