Differences in the ages, sexes and physical condition of Starlings Sturnus vulgaris at the centre and periphery of roosts

The differences between individuals at the centre and at the periphery of social groupings of birds have been demonstrated, but night‐time roosts have received little attention. Here, the effects of age, sex and physical condition on the structure of Starling roosts were investigated. It was found that the dispersion of different age and sex categories was heterogeneous; proportionately more adult males occurred in the centre compared with the periphery, and proportionately more first‐year females occurred on the periphery compared with the centre. Birds in the centre were heavier than peripheral ones irrespective of differences in body‐size. We propose that the centre of the roost is the preferred location and that the observed dispersion reflects dominance.