Bird odour predicts reproductive success

Although the importance of chemical communication in birds has long been overlooked or doubted, volatile compounds in avian preen secretions have been shown to covary with traits including species, sex and breeding condition, and thus may be useful mate recognition cues. Here we demonstrate for the first time that these compounds may reliably predict reproductive success in a North American songbird, the dark-eyed junco, Junco hyemalis. Several compounds associated with sex differences in this species varied with reproductive success, such that females with a more 'female-like' volatile profile and males with a more 'male-like' profile produced more genetic offspring. A male's preen oil volatile compounds also predicted his success in rearing offspring in his home nest: males with a higher abundance of 'male-like' compounds had more surviving nestlings, including offspring sired by extrapair males. Finally, males with a higher abundance of 'female-like' compounds had more extrapair offspring in their home nests. Our results suggest that odours correlate with reproductive success and thus have qualities that could allow them to serve as reliable mate assessment cues in birds.