Male song individuality over female breeding periods in Savannah sparrows (Passerculus sandwichensis)

Song individuality in songbirds is a prerequisite for individual recognition, which plays an important role in communication between pair members, relatives, or neighbors. We investigated song individuality of Savannah sparrow (Passerculus sandwichensis) males over a single breeding season. We recorded songs from 11 color-banded males during each of the four female breeding periods (pre-pairing, pairing and egg-laying, incubation, and nestling and fledging). We analyzed 10 songs from each male, with 13 temporal and nine frequency variables that represented the structural characteristics of songs to examine individual variation throughout the breeding season. The results of nested analysis of variance (ANOVA) showed that all song variables differed among individuals across breeding periods and among breeding periods across individual songs except for F9 (peak frequency difference between the first and the second trill parts). A discriminant function analysis showed that songs of pre-pairing periods were clearly separated from those of the other periods. These results suggest that the songs of males display individuality and maintain potential information about his mating status and his mate's reproductive condition across the breeding season.