High microhabitat heterogeneity drives high functional traits in forest birds in five protected forest areas in the urban mosaic of Durban, South Africa

Anthropogenic forest disturbance poses a significant threat to the persistence of wildlife. Generally, disturbance of forest environments alters vegetation structure, affecting specialised niche-dependent avian species. We investigated the influence of a comprehensive suite of vegetation structures on the taxonomic and functional diversity of avian forest species in five protected forest areas in the urban mosaic of eThekwini Municipality, Durban, South Africa during the austral breeding season of 2016. We conducted 135 fixed-radius point-count surveys between the vegetation classes of Indigenous Forest (IF) and Coastal Thicket/Dense Bush (TDB; a secondary wooded-habitat that represents regenerating Indigenous Forest), and recorded microhabitat structure covariates at each survey site. We conducted RLQ analyses to examine the association between avian functional traits and microhabitat structures present at each survey site. There was no significant difference in vegetation structure nor species richness between IF and TDB. Species with specialised ecological niches (e.g. large-bodied frugivores; small-bodied insectivores, cavity-nesters) were present in both IF and TDB, indicating that TDB in Durban represents an advanced stage of forest regeneration. We highlight the importance of both IF and TDB for providing critical habitat for both avian generalised and specialised functional traits in the forest patches in the urban mosaic. Crucially, we show that forested areas under conservation management in urbanised areas successfully provide species with a wide variety of functional traits critical to ecosystem functioning and human health. (C) 2019 The Authors. Published by Elsevier B.V.