Hitting all the notes : Connecticut warblers sing an extended song type

Abstract

Birds use songs to communicate with mates and rivals and thus these signals have important social and fitness consequences. Understanding the pattern of vocalization and repertoire use of a species is valuable for population monitoring and species recovery plans. The Connecticut Warbler (Oporornis agilis) is an enigmatic passerine bird for which we know little about its vocal repertoire and behavior. We examined autonomous recordings from boreal avian monitoring projects from Ontario, Canada, and discovered a previously undescribed extended song type, similar to that of other related warbler species. Extended songs are composed of a number of syllables including the species’ primary song and averaged 7.1 ± 0.2 s (SE) in length, five times longer than primary songs. The song appears to have a structure similar to Ovenbird (Seiurus aurocapilla) and Common Yellowthroat (Geothlypis trichas) song with introductory syllables preceding the first primary syllables followed by a mix of terminal syllables that were often interspersed with additional primary syllables. Individuals have on average 13.0 ± 0.5 different syllables and songs are composed of 10.8 ± 0.2 syllable types and 14.8 ± 0.4 total syllables. While primary songs occurred more often before sunrise and throughout the morning, extended songs were more often detected before and after sunset suggesting temporal separation in song type use. Our results extend our understanding of the vocal behavior of the Connecticut Warbler and related species within the Oporornis-Geothlypis complex.