Breeding ecology of African Woolly-necked Storks (Ciconia microscelis) in a human-modified, mosaic landscape in South Africa

Abstract

Abstract In recent decades, the population of the African Woolly-necked Stork ( Ciconia microscelis ) in South Africa has rapidly expanded into mosaic landscapes with high human density in KwaZulu-Natal Province. We investigated (1) the basic breeding natural history details of Woolly-necked Storks, (2) whether nest sites were selected in areas of greater residential land cover, and (3) what factors influenced breeding outcomes. We monitored 169 nesting attempts at 96 nest sites during three breeding seasons (2022–2024). Pairs fledged a mean of 1.03 nestlings per annum (including unsuccessful nests), and the apparent nest survival rate was 61.8%. Storks showed significant selection for sites in areas with more residential land cover. Rainfall 30 days prior to nest initiation negatively affected breeding outcomes, which likely reflects the need to time nesting to coincide with peak natural prey abundance for provisioning young in spring. Woodland/forest land cover around nests positively influenced fledging success, which is probably a reflection of the need for natural areas in the urban mosaic to forage during nestling provisioning. Finally, the presence of nest helper(s) negatively influenced breeding outcomes, suggesting that this unique behavioural modification for this species in urban areas is maladaptive. Whilst the ecological trade-offs of urban life for Woolly-necked Storks remain opaque, the overall moderate breeding success we found demonstrated some meaningful benefits to reproduction that have likely contributed to continued population expansion in South Africa.