Song Learning as Evidenced from Song Sharing in Two Hummingbird Species (Colibri coruscans and C. thalassinus)

We have demonstrated that male hummingbirds in the genus Colibri share song types. The Sparkling Violetear (C. coruscans) from an Ecuadorian population and Green Violetear (C. thalassinus) from populations in Costa Rica form aggregates or neighborhoods. Males of a neighborhood sing the same song type and those of distant neighborhoods have different song types. The resultant geographic variation in song, we suggest, is due to cultural drift acquired through song learning. Song sharing was determined not only by traditional, visual examination of spectrograms of song but with a relatively new, digital cross-correlation method that permits statistical treatment. The statistical procedures included cluster analysis that reflects the distribution of songs in geographic space and an evaluation for randomness of that distribution by use of the Mantel test.