Early learning affects social dominance: interspecifically cross-fostered tits become subdominant

Social dominance influences the outcome of competitive interactions over limited resources, and may hence be important for individual fitness. Theory thus predicts that its heritability will be low and that non-genetic determinants of dominance should prevail. In this field experiment we reciprocally cross-fostered great tits (Parus major) to blue tits (Parus caeruleus) to investigate the impact of early social experience on dominance status in competition over food during winter. Controlling for potential effects of age, size, sex and site-related dominance, we show that cross-fostered birds of both species were subdominant to conspecific immigrants, while controls originating from unmanipulated broods were dominant to conspecific immigrants. Furthermore, blue tits reared by blue tit parents but with at least one great tit broodmate had lower dominance status relative to conspecific immigrants than did controls. Although great tits generally dominated blue tits, cross-fostered birds of both species initiated marginally more fights against the other species than did their respective controls, suggesting faulty species recognition. Since both social parents and broodmates strongly influence the dominance behavior of offspring later in life, we conclude that social conditions experienced at an early age are crucial for the determination of subsequent social dominance.