Social dominance and survival in flocking passerine birds: a review with an emphasis on the Willow Tit Parus montanus

Abstract

Many birds spend the non-breeding season in flocks which exhibit a clear social hierarchy. This review outlines survival of passerine birds which live in such flocks . Survival is examined in relation to social dominance and to differences in behavioural patterns which may be associated with differences in survival probability. This paper has an emphasis on Parus species and especially on the Willow Tit (P. montanus) which is becoming a model species as far as the non-breeding season is concerned. Social dominance is viewed here as a relative measurement, not as a fixed property of an individual . One individual, the dominant, is typically defined as consistently having priority to access resources over another individual, the subordinate. This review concentrates on the following subjects : (1) The social organization of winter flocks ; (2) Social influences on food caching; (3) The activity times of dominants and subordinates in relation to predator-risky times; and (4) The timing of mortality and importance of food on survival in dominance-structured flocks . Moreover, the seemingly paradoxical winter sociality is discussed: why do subordinate birds stay in flocks even though they are less likely to survive winter than dominants?