CORRELATES OF AGONISTIC DISPLAY BY GREAT TITS PARUS-MAJOR

This study examined physical and social correlates of agonistic display performance by wild great tits Parus major competing over food and territorial space. All behavioural data were collected at winter feeding stations from individually colour-ringed birds for which data on physical characteristics, current social status and individual history were available. At feeders, competitive interactions between males were more frequent than those involving females, and birds not present in previous winters (mostly first-winter birds) interacted more frequently than prior residents (locally territorial adults). Interactions away from food sources usually involved at least one male, increased in frequency over the course of the winter, and often involved chasing of one bird by another. These interactions are thought to reflect competition for territorial space. Males were almost always dominant over females in competitive interactions. Simple supplants were most frequent in intersexual interactions, with display being more often seen in interactions between birds of the same sex. In intrasexual interactions, there were no consistent differences between the sexes in frequency of use of displays, but there was a general trend for postural display elements to be performed more often by eventual dominants than by eventual subordinates. Displays based on 'head-up' tended to be performed by prior resident, locally dominant, territorial males. Their incidence increased over the course of the winter, and they were especially associated with non-feeder interactions. Displays based on 'wings-out' and 'tail-fanning' were associated with non-territorial, first-year birds that were less frequently occurring at the study site, and tended to occur in cases where the opponents had little prior experience of each other. Displays based on head up were performed almost exclusively in intraspecific interactions, whereas those based on wings out and tail fanning were also common in contests over food with blue P. caeruleus and coal tits P. ater, in which the great tit was usually dominant.