Repertoire size, territory acquisition and reproductive success in the song sparrow

Abstract

Song repertoire size, time to first territory acquisition, territory size, territory tenure and lifetime reproductive success were measured in males of known age in a wild, resident population of song sparrows, Melospiza melodia. One-year-old males had smaller repertoires than older males, but this apparent change in repertoire size was due to attrition of individuals with small repertoires rather than to an increase in the repertoire size of individuals with age. Males with large repertoires held territories longer and had greater annual and lifetime reproductive success than males with small repertoires. Half-hour repertoire size, which may represent an ecologically more relevant measure of repertoire size perceived by a transient listener, was also positively related to territory tenure and annual reproductive success. Thus listeners might be able to assess a singing male's competitive ability without sampling the entire repertoire.