Seasonal song variation in male Carolina Wrens (Thryothorus ludovicianus)

Abstract

Birdsongs primary function is attracting and stimulating mates and repelling rivals during the breeding season. However, many species also sing during the nonbreeding season, which raises questions about the function of nonbreeding song and the proximate mechanisms underlying its production. In this study, we compared spectral and temporal measurements from a large sample of breeding (N = 267) and nonbreeding songs (N = 283) of Carolina Wrens (Thryothorus ludovicianus), a nonmigratory, temperate species that sings year-round. We found that breeding songs were longer than nonbreeding songs and had more syllables within each song. Trill rate, the number of notes per syllable, minimum and maximum frequency and frequency bandwidth did not differ detectably between the two seasons. This study is the first to examine seasonal song differences in Carolina Wrens and provides a basis for future investigations into the drivers behind this seasonal variation.