WHY DOES DOMINANCE DECLINE WITH AGE IN WINTERING SNOW BUNTINGS

The influence of sex and age on success in contests over access to foo d was studied in a wintering population of snow buntings, Plectrophena x nivalis, in northeast Scotland over a 5-year period. Males won 87% o f dyadic interactions with females, but, in contrast to many other stu dies, first-winter birds won a majority (60-70%) of intra-sexual inter actions with same-sex adults. First-winter males continued to have gre ater success than adult males even after controlling for an individual 's role within a contest, the degree to which the contest escalated, a nd the severity of the weather. Contests won by adult males were more likely to have escalated, perhaps indicating a greater cost, than thos e won by first-winter males. Dominance status dropped from an individu al's first to its second winter of life, but not thereafter. It is arg ued that winning winter food fights is of more immediate benefit to fi rst-winter birds, and that reversal of the usual age-related dominance pattern may be due to the species' itinerant nature in winter combine d with a lack of long-term pair-bonds or individual recognition. Asser tion of dominance therefore carries only short-term benefits which may not override the costs of aggressive behaviour. (C) 1997 The Associat ion for the Study of Animal Behaviour.