Structure, frequency of usage, and apparent learning in the primary song of the yellow-throated vireo, with comparative notes on solitary vireos (Aves: Vireonidae)

The primary song of 27 yellow-throated vireos (Vireo flavifrons) from throughout their breeding range in eastern North America was examined spectrographically. Only 39 different song phrases were found, and each bird sang an average of only 5 phrases. There is, therefore, a great deal of overlap in the phrases sung by birds in any part of their range. Yellow-throated vireo primary song phrases are characteristically frequency modulated like those of the solitary vireos (Vireo solitarius) of western North America, but no phrases of the two species were identical. Male yellow-throated vireos sang a number of the same few song phrases at different times during the breeding season. Distinct changes in timing and the overall amount of singing, however, indicate the importance of these two factors for intraspecific communication. The discovery of a yellow-throated vireo singing primary song phrases characteristic of solitary vireo song seems to indicate that, to a large extent, primary song is learned, and that much of the learning takes place early in the bird's life.