Spring roosting dynamics of red-winged blackbirds: biological and management implications.

A spring blackbird roost near Beauharnois, Quebec, became active in the middle of March; most birds had dispersed by late April. Throughout the roosting period, Agelaius phoeniceus constituted c.74% of the roosting population. The patterns of arrival and dispersal from the roost by the different age-sex cohorts of the red-winged blackbird reflected the intensity of sexual selection on this polygynous species. Older males were first to arrive but dispersed to establish breeding territories soon after. Second- year males exhibited a less abrupt pattern of arrival and dispersal than older males while the pattern for females was even less abrupt.- from Authors