Late song learning in song sparrows

In many oscine species, young males learn songs that match those of their first breeding-season neighbours. Because sharing songs with neighbours may be advantageous, selection should favour birds that retain the capacity to memorize new songs later in their first year as the birds cannot know for sure who their neighbours will be until spring. We investigated whether song sparrows, Melospiza melodia, from a sedentary western population were capable of acquiring new songs after their natal summer in a two-stage laboratory experiment. In the first stage (30–90 days of age), we rotated hand-reared males equally among one set of four live tutors that had been neighbours in the field (and therefore shared songs between them). During the second stage (140–330 days old), we removed two of the original tutors and replaced them with two new tutors (which did not share any songs with the original tutors). During stage two, subjects were not rotated, but were stationed next to only one of the four tutors (they could hear the other three at a distance). Eight of 12 subjects learned songs from tutors they only heard after they were 140 days old, and six subjects learned most of their songs from a late tutor. Thus, sedentary song sparrows are capable of acquiring many songs de novo in late autumn. These results are consistent with a song-learning strategy that provides young male song sparrows with a repertoire of songs they will share with their first breeding-season neighbours.