ECOLOGICAL ISOLATION IN GREYWING AND REDWING FRANCOLINS

Abstract

Summary Mentis, M. T. & Bigalke, R. C. 1981. Ecological isolation in Greywing and Redwing Francolins. Ostrich 52:84-97. The Greywing Francolin Francolinus africanus and Redwing Francolin F. levaillantii are closely related, of similar size, and live in superficially similar habitats. Their ranges overlap, and ecological isolation was studied in the Natal Drakensberg where partial sympatry occurs In the study area, Greywing Francolins occurred above 1840 m a.s.l. and Redwing Francolins below 2450 m a.s.l. Within the zone of sympatry there was a partial polarization with Greywing Francolins in sparse, short grass at high elevations, and Redwing Francolins in denser, taller grass at low elevations. The abundance of the birds did not differ in relation to slope, aspect and vegetation type. The principal diet of both species was composed of the corms and tubers of grassland geophytes. The birds ate the same species of geophytes but in different proportions. Greywing Francolins ate small volumes of food of apparently high nutritive value, while the reverse applied to Redwing Francolins. Within the zone of sympatry the two birds are apparently not isolated ecologically, but are in partial competition.