THE INFLUENCE OF AGE AND ACCESS TO FEMALES ON DOMINANCE IN CAPTIVE MALE BROWN-HEADED COWBIRDS (MOLOTHRUS ATER)

Pairs of captive male brown-headed cowbirds (Molothrus ater) housed with a female formed clear dominance relationships, and when an older male was housed with a yearling male, the adult was usually dominant. When the dominant male was removed to allow the subordinate male exclusive access to the female for 2 days, the subordinate became dominant in 5 of 19 (26.3%) trials when the males were placed together again. However, in 1 of 10 control trials, the subordinate male became dominant without having access to a female for 48 h, which suggests that access to a female was not the only reason for such status switches. Subordinate yearlings were as likely as subordinate adults to reverse their status. Size did not distinguish dominant from subordinate males or individuals that changed status from those that did not. However, subordinate males that became dominant displayed more when alone with the female than males that remained subordinate.