Male badge size predicts dominance against females in House Sparrows

We investigated dominance relationships and the use of male badge size as a status signal in a mixed-sex hock of House Sparrows (Passer domesticus). S pecifically, we tested whether females differ from males in their fighting behavior or dominance status, and whether badge size predicts dominance and fighting success of males in male-female fights. We found that both sexes were involved frequently in aggressive encounters, and the mean dominance r ank of males did not differ from the mean rank of females. Badge size was t he only significant predictor of the dominance rank of males, and was a goo d predictor of their aggressiveness measured as the proportion of fights: i nitiated. On the other hand, female dominance rank was correlated with body weight. In male-female fights, both the proportion of female-initiated agg ressive interactions and the proportion of fights won by females decreased with increasing size of the opponent's badge. Large-badged males dominated more females in dyadic interactions than smaller-badged males. These correl ational results suggest that male badge size may be used as a signal of dom inance status between male and female House Sparrows in winter flocks.