BENEFITS AND COSTS OF DOMINANCE AND SUBORDINANCE IN WHITE-CROWNED SPARROWS AND THE PARADOX OF STATUS SIGNALING

Benefits and costs of dominance and subordinance in wintering white-crowned sparrows, Zonotrichia leucophrys gambelii, attracted to a feeding site were assessed via focal animal sampling. Data were grouped by age-sex classes, which have plumage differences that serve as status signals. Win-loss records ranked the classes from dominant to subordinate as follows: adult males, adult females, immature males and immature females. Adult males initiated aggression at the highest rate and immature females almost never initiated aggression. Surprisingly, immature males initiated aggression as often as adult females although there were fewer individuals they could dominate. Nearly all results indicated that dominance is beneficial and subordinance costly. Only adult males won interactions more often than they lost. Immature females fed for shorter intervals than more dominant classes. Aggression was generally towards subordinate classes instead of in a like versus like pattern. Losses immature birds experienced to adults were less costly in terms of losers leaving the feeding area and/or being chased than were losses by immatures and adults to their own age classes. The results provide no strong evidence that subordinates would suffer increased costs if they cheated by mimicking the plumage of a dominant class. If social costs contribute to the evolutionary control of cheating, they probably do so only during the beginning of the winter season when flocks are forming but even here the evidence for social costs is tenuous. © 1991 The Association for the Study of Animal Behaviour.