Coloniality of birds in the Kalahari – spatial distribution of trees and nests of the Sociable Weaver (Philetairus socius)

Abstract

The spatial distribution of suitable nest sites is a limiting resource for many colonial breeding animals. Therefore, we investigated and mapped the spatial distribution of nests of Sociable Weaver (Philetairus socius) to evaluate whether the size and distribution of suitable nesting trees influences the variability of colony size and spatial distribution of colonies in two study sites in the Kalahari, South Africa. We used spatial statistics to describe characteristics of point patterns. Nests of communal weavers were clustered at distances up to 300 m, whereas nests were distributed regularly at distances greater than 1,000 m. We therefore suggest that functional colonies of the social weaver consist of several nests on adjacent trees. From our analyses the question arises why sociable weavers establish sub-colonies instead of adding more chambers to the natal nest.