Patterns of Dominance and Aggressive Behavior in Blue Jays at a Feeder

Abstract

We studied interactions among Blue Jays (Cyanocitta cristata) visiting a feeder in south-central Florida over a 4-year period to examine the influence of sex, time of year, and body size on dominance and aggression, describe changes in dominance among individuals over time, and test for the presence of linear dominance hierarchies. Males dominated females throughout the annual cycle, and in all 24 of the male-female significant dyads. We cannot reject the hypothesis that male dominance over females results from the larger body size of males. We infer that males also were more aggressive than females because they were involved in more interactions than expected by chance. Females became more, and males became less, aggressive immediately prior to the breeding season, but fluctuations in aggression did not lead to shifts in intersexual dominance. Dominance relationships among a few high-ranking males were intransitive and changed over time. Dominance hierarchies, characterized by reversals, circular triads, and unknown relationships, were not linear. Whereas linear hierarchies have been shown to exist in New World jays that live in small, stable social groups, we suspect the variable constituency and instability of flocks precludes the emergence of strictly linear hierarchies in the genus Cyanocitta.