Social Dominance and Energy Reserves in Wintering Woodland Birds

To understand animals' tactics for surviving the winter season, we need to know how they manage their energy reserves. Fat reserves in small birds in winter generally increase with starvation risk. Studies have documented higher fat reserves in response to various sources of variability in energy intake or expenditure. Using three woodland species, Carolina Chickadee (Poecile carolinensis), Tufted Titmouse (Baeolophus bicolor), and White-breasted Nuthatch (Sitta carolinensis), we tested the prediction that the more predictable food supply of socially dominant animals enables them to maintain lower energetic reserves than subordinate conspecifics. We inferred dominance from age and sex categories. The hypothesis was fully supported. In all three species, dominants carried relatively lower fat reserves than subordinates.