Social organization and mating success in local song populations of village indigobirds, Vidua chalybeata.

Behavioral interactions among color-marked individual Vidua chalybeata that shared common song dialects were observed for 5 years in two populations at Lochinvar National Park, Zambia. Social interactions involved males visiting and competing for mating sites and female visiting male in an apparent sampling of potential copulating partners. Differences in mating success among the polygynous males were compared with male behavior and territory resources, and criteria were developed to test the importance of intrasexual male competition and female mate choice in explaining the mating system of the populations. Song behavior best explained differences in mating success of males, with lesser effects of neighboring males and the defensible resources around the call-sites. The social organization of song populations resembles that of a dispersed lek with females visiting many males but mating with few males. We discuss the observations on indigobirds in relation to behavioral selection, sexual selection, and mating systems. Mating systems of certain populations and species are compared using statistics of individual mating success.