SONG POPULATIONS AND DISPERSAL IN STEELBLUE AND PURPLE WIDOWFINCHES

Payne, R. B. 1985. Song populations and dispersal in Steelblue and Purple Widowfinches. Ostrich 56:135-146.

Songs of Steelblue Widowfinches Vidua chalybeata were recorded over eight years at Lochinvar National Park, Zambia. Neighbouring males share their song-type repertoires. Individual birds changed the structural details of all song types in their repertoire from year to year, and over 4–5 years the songs accumulated changes so that a song type could scarcely be recognized as the same. A few males in addition switched their song repertoires when they dispersed from one song population to another, or when their old neighbours disappeared and new neighbouring males sang a different song repertoire. Individual marked adult birds moved from one song neighbourhood to another. Purple Widowfinches had a similar song behaviour but only one song dialect was found in the study area.

An estimate of the proportion of immigrants was made from the proportion of birds with songs unlike their neighbours, and from birds that had a mixed song repertoire or that switched their song repertoires. Song populations were sampled at several localities in the Transvaal, Botswana, Zambia, Kenya, Tanzania, Cameroon, and Nigeria. An overall minimal estimate of dispersal between song neighbourhoods was 18 %. The incidence of observed dispersal and the movements indicated by the song differences among local widowfinches were considerable and more than sufficient to prevent genetic isoloation and differentiation of local song populations.