Learning what (not) to do: testing rejection and copying of simulated heterospecific behavioural traits

Animals can copy behaviour of heterospecifics (interspecific social learning), but it is not known whether social-learning strategies postulated for conspecific contexts, such as selectively copying individuals (or behaviours) that are more successful or common than the observer, apply here. A recent study found evidence for biased interspecific acquisition of nest site feature preference depending on observed fitness of the demonstrator (clutch size). We experimentally tested whether migratory pied flycatcher, Ficedula hypoleuca, females, given a choice between two novel alternative behavioural traits of nest site feature choice, copy or reject the experimentally induced choice exhibited by simulated resident tit (Parus spp.) nests, when those nests portray a high or low fitness correlate (clutch size). Flycatchers were more likely to choose the opposite trait when the exhibited choice was associated with low simulated tit clutch size, demonstrating active rejection. Flycatchers had a strong overall preference to take over the tit nest site. We conclude that animals in the wild can respond to observable heterospecific fitness correlates when making decisions. Our experiment confirmed the existence of a strategy to reject behaviours exhibited by poorly performing individuals, complementing the already proposed social-learning strategies. By affecting the niche overlap of co-occurring species utilizing similar resources, interspecific social learning may affect species interactions and community structure.