Habitat Segregation of Male and Female Red-Backed Shrikes Lanius collurio and Lesser Grey Shrikes Lanius minor in the Kalahari Basin, Botswana

Abstract

Lesser Grey Shrikes and Red-backed Shrikes have much smaller ranges on the non-breeding grounds in the Kalahari basin than during breeding. This study investigated whether, as a result of competition, habitat segregation occurs on the non-breeding grounds. Migrant shrikes were surveyed in point-transect counts in 19 vegetation types in Botswana. There were clear differences in habitat distribution between the species, and also between the sexes in the Red-backed Shrike. Female Red-backed Shrikes occupied more densely wooded bushveld than males, while Lesser Grey Shrikes occupied the most open habitat and overlapped more frequently with male than with female Red-backed Shrikes. More subtle differences along gradients of herbaceous ground cover suggest that differences in habitat quality may be involved, the dominant species (Lesser Grey Shrike) occupying, on average, the best and the most subordinate birds (female Red-backed Shrikes) the poorest habitat. The sex differences in habitat occupation on the non-breeding grounds in the Red-backed Shrike are the first such differences documented in any PalaearcticAfrican migrant passerine.