Multiple sub-repertoires and singing patterns of Red-eyed Vireos (Vireo olivaceus)

Abstract

Some songbirds produce only one or a few song types, but others sing large repertoires with many different song types. Birds with large repertoires can arrange these songs in a variety of distinct singing patterns that add a layer of complexity to their vocal production. Both large repertoires and singing patterns may communicate important information to conspecific males and females. Previous estimates of repertoire size of Red-eyed Vireos (Vireo olivaceus) range from 39 to 59. These estimates were based on a small number of recorded phrases per individual, and on single recordings of most individuals. I have made lengthy, multiple recordings over periods of days and weeks of 46 Red-eyed Vireos to revisit the question of their repertoire size. Repertoire size estimated for the birds I recorded varied between 17 and 341 phrase types, with a mean of 91. Fourteen birds for which I recorded at least 1,000 phrases had a mean repertoire of 154 phrase types. Previous estimates may have been low by a factor of 2–3 because of limited sampling. Plotting of phrase type vs. phrases sung for each bird showed a variety of singing patterns. Six birds sang a single limited repertoire of 17–47 phrase types. Nineteen birds sang a single repertoire, but new phrases continued to be added as more recordings were made, so these repertoires had no clear size limits. Twenty birds sang multiple groups or sub-repertoires of phrase types at different times, often changing between sub-repertoires during a single continuous bout of singing. Five birds sang frequent repetitions of a small number of phrase types selected from larger repertoires. The mean singing rate of the birds studied climbed from a low of 33 phrases/min at the beginning of the breeding season to a high of 46 phrases/min at the peak, and declined to 34 phrases/ min at the end of the breeding season. My study shows that Red-eyed Vireo repertoires are significantly larger than previously estimated, that singing patterns vary widely among individual birds, and that many birds group phrase types into multiple sub-repertoires, sung at different times.