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 hig her fat reserves in response to various sources of variability in energy in take or expenditure. Using three woodland species, Carolina Chickadee (Poec ile carolinensis), Tufted Titmouse (Baeolophus bicolor), and White-breasted Nuthatch (Sitta carolinensis), we tested the prediction that the more pred ictable food supply of socially dominant animals enables them to maintain l ower energetic reserves than subordinate conspecifics. We inferred dominanc e from age and sex categories. The hypothesis was fully supported. In all t hree species, dominants carried relatively lower fat reserves than subordin ates.