Song-type sharing and matching in a bird with very large song repertoires, the tropical mockingbird

Song-type matching, a behaviour of some songbirds in which one individual replies to another’s song with a matching song type, has been studied primarily in birds that have small to moderately sized song repertoires (<15 song types) and that share only a few song types with neighbours. Few previous studies have examined song-type matching in species with very large song repertoires, in which birds can share larger numbers of songs with neighbours and matching particular song types might be more challenging. Here we describe frequent and rapid song-type matching in a population of tropical mockingbirds, Mimus gilvus. Males had repertoire sizes of about 133 distinct song types on average which were delivered with high versatility. Territorial neighbours shared significantly more song types than did nonneighbours, and neighbouring males matched each other’s songs frequently and often with surprising speed. Overlapping of songs occurred at approximately chance levels. Song-type matching in these birds could indicate more than just aggressive intentions, which is the presumed function of this behaviour in species with smaller repertoires. In tropical mockingbirds, rapidly matching the songs of neighbours could provide information to listeners about a singer’s experience or abilities.