No genetic evidence for parent–offspring relatedness in post-breeding social groups of Black-crested Titmouse (Baeolophus atricristatus)

After the breeding season, territorial adult Black-crested Titmouse (Baeolophus atricristatus) and residing juveniles form social groups that may persist until the following spring. Under the prolonged brood care hypothesis, one would expect these juveniles to be retained offspring with delayed dispersal of the breeding pair. To test if Black-crested Titmouse juveniles that reside in post-breeding territories are offspring of the territorial adult male, we performed microsatellite-based paternity analyses of 6 juvenile–adult male social dyads on 6 different territories. None of the juveniles were offspring of the adult male with which it shared a territory. We discuss several possible evolutionary explanations for this result.