Birdsong learning is mutually beneficial for tutee and tutor in song sparrows

Song learning is generally assumed to be beneficial for a young songbird, but merely incidental, without costs or benefits, for the older song ‘tutors’. In the present study we contrast two mutually exclusive hypotheses about the tutor/tutee relationship: (1) that it is cooperative, or at least mutually tolerant, with tutor and tutee mutually benefiting from their relationship, versus (2) that it is competitive, with tutor and tutee competing over territory, so that one or the other suffers negative fitness consequences of their relationship. In a field study of three consecutive cohorts of song sparrows, Melospiza melodia morphna, we determined the older bird (primary tutor) from whom the young bird (tutee) learned most of his songs, and how long tutee and primary tutor survived subsequently. We found that the more songs a tutee learns from his primary tutor, the longer their mutual survival on their respective territories. While the number of songs they share predicts the mutual survival of tutor and tutee, it does not predict the independent survival of tutor or tutee, suggesting that the benefit each receives from song sharing exists only so long as both survive.
National Science Foundation; University of Washington Royalty Research Fund