Spatial use of African Woolly-necked Storks (Ciconia microscelis) in a South African mosaic landscape

Abstract

African Woolly-necked Storks (Ciconia microscelis) were conventionally considered shy and secretive, occurring in natural wetlands and swamp forests. However, these storks rapidly colonised urban areas of KwaZulu-Natal, South Africa, since the early 1990s. We studied the spatial use of Woolly-necked Storks in the colonised region using telemetry, hypothesising that the abundance of urban food (e.g., supplementally-fed anthropogenic food, refuse, and natural prey in residential gardens) has led them to be highly sedentary. Using measures of utilisation distribution size, nesting foraging trips, and nocturnal roost site fidelity, we found that adults had much more limited spatial use than immatures. Furthermore, adults strongly selected for urban and rural residential habitats, whereas immatures showed weaker selection for more types of habitats, yet seasonal effects were weak for both age groups. Urban areas of KwaZulu-Natal clearly confer meaningful fitness benefits to breeding adult woollynecks that are not yet realised during the immature life stage. Immatures move widely during the post-dispersal period because they are not constrained by breeding considerations, and their spatial use may be influenced by social aspects. Given KwaZulu-Natal’s rapid natural habitat loss and urban sprawl, our findings offer a fairly unusual perspective on the effect of urbanisation on wildlife and their persistence in urban mosaic landscapes with natural and managed green spaces in South Africa.