Song Features as Species Discriminants in American Warblers (Parulidae)

Using multivariate discriminant analysis, we examined 337 songs of 19 species of wood warblers sympatric in New Brunswick, Canada. We divided the warblers into five overlapping groups of species based on habits and songs. Our hypothesis was that song features would be the most reliable at high noise levels or under conditions of poor transmission. Hence, we predicted that within most of these groups the songs would segregate highly on the basis of song features alone, as opposed to features of individual sounds or phones. In four of the groups the analysis correctly classified 84 to 95% of the songs on the basis of song features alone. In Group 5 (Yellow, Chestnut-sided, Redstart, Magnolia warblers), only 68% were correctly classified on the same basis. The addition of phone features to discrimination for this group increased the correct classification to 85%. In some groups the frequency modulation patterns of the phones are so simple that they contribute little to improved discriminations. The relative contributions of phones may be functionally related to the importance of possible competitors, the distance of the communication and other noise factors, and to the relative development of repertoires.