Song learning in the wood thrush

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Abstract
A typical wood thrush (Hylocichla mustelina) song has three phrases. The first (A) is a series of low pitched sounds, the second (B) consists of loud flutelike notes, and the third (C) is usually a trill. Males have repertoires of two to eight different B phrases, which they use in different songs. In a previous study, males reared in isolation of adult song developed songs that were normal except for the structure of the B phrases. We tutored young males (at age 20–80 days) with recorded B phrases. The phrases were of four previously defined structural types, with four variants of each type, giving a total of 16 phrases. The variants of each type differed only in frequency (Hz). The objectives of the experiment were to determine (i) if wood thrushes copy the structure of B phrases that they hear as juveniles, and (ii) if they copy selectively in such a way as to develop repertoires of highly contrasting phrases. Results were obtained for five males. The B phrase repertoires developed by four subjects consisted entirely of phrases (N = 17) copied from the tutor tape. The repertoire of the fifth subject was of phrases (N = 4) that appeared not to be copied. The males that copied from the tutor tape showed no tendency to develop repertoires of highly contrasting B phrases. Three of the four males developed multiple versions of one or more phrase types, while ignoring other types, and in some cases these versions were very similar in frequency and other details of structure.