Territorial song and song neighbourhoods in the Scarlet Rosefinch Carpodacus erythrinus

Abstract

Throughout the range of the Scarlet Rosefinch, its territorial song consists of 3–9 (usually 4–5) elements, of which there are 5 different types. The differences lie in the way the pitch of the element changes in time (frequency “slope”) and the width of the frequency band. Within a given type of song, the various elements can be present in almost any combination. Therefore, so many song types can be formed that the songs in even small parts of the species’ area are clearly distinct from one another. Despite this capacity for variation, however, by chance identical songs may be sung in widely separated parts of the area, in some cases by different subspecies. The species has not developed large-scale dialects or regiolects based on a song tradition acquired during an early imprinting phase. Scarlet Rosefinches tend to breed in small colonies, groups of up to about 15 pairs characterized by the same type of song (song neighbourhoods, formed by the development of a microlect). Microlects develop by a founder effect. When males, near one-year old or older, join one another to form isolated colonies after arrival in the breeding region, they adopt (“learn”) the song type that will eventually characterize the colony from the first male to arrive at the site. After the colony has been founded, in most cases each male uses only one type of song during a breeding season, with practically no variation of the temporal and frequency parameters. Singing the same type of song, the members of a colony accept one another sufficiently to allow the breeding territories to be closely packed. It appears that a long-lasting capacity for acoustic learning, in combination with colony-like breeding and great ecological flexibility, has allowed the Scarlet Rosefinch to become the most successful species of the genus Carpodacus.