Avian community changes along an urbanization gradient in Dar es Salaam, Tanzania, with a reversed trend for alien species

Abstract

Dar es Salaam is the most populous city in Tanzania with over five million people, and has the fastest growing human population in East Africa. We examined the change in avian species richness and abundance along an urbanization gradient from city centre to peri-urban in order to provide insights into impacts of urbanization on native and non-native avifauna. Four major city exit/entry roads were used as reference transects in counting birds and recording selected urbanization indices at 63 circular points positioned at approximately 1 km intervals. A total of 1964
individuals from 71 species belonging to 36 families and nine orders were detected. Species-abundance patterns of native birds increased along the urbanization gradient from urban to peri-urban. However, the alien House Crow and House Sparrow showed reversed abundance trends from city centre towards peri-urban. These patterns were significantly related to the shift in urbanization indices; the number of pedestrians and vehicles, and percentage cover changes for buildings, pavements, bare land, and vegetation. Avian dietary guilds varied across the urban-peri-urban stretch and were significantly influenced by the vegetation cover. This study revealed that continuing urban development has a great impact on avian communities. We therefore recommend urban planning to be geared to controlling alien avian species population and increasing the vegetation cover.

Keywords: Alien species, biotic homogenization, dietary guilds, House Crow, urbanization