Dominance-Specific Vigilance in the Great Tit

Abstract

A bird foraging at concentrated food sources such as artificial feeders or carcasses of wild animals, irrespective of its dominance rank, may be preyed upon by airborne predators with a greater probability than other flock members foraging under protective cover. Field observations on 15 free-ranging Great Tit Parus major basic-flocks were carried out to examine whether duration of anti-predator vigilance and foraging at feeders is related to social rank, group size and location of a feeding site within a communal flock territory. The proportion of time spent scanning was positively correlated with dominance rank. Removal experiments supported results of field observations revealing a causal relationship between rank and ability to choose the safest foraging behaviour. This result suggests that dominants can benefit directly from their personal vigilance. The lack of a relationship between flock size and vigilance time of dominants also provides evidence for a direct benefit of being vigilant. Dominants were free to scan more than subordinates only within their home ranges. When visiting home areas of neighbouring basic-flocks, dominant individuals lost their priority. This supports results of previous studies that there is a site-related dominance in the Great Tit.