A comparison of the bird fauna of two foothill forests in Tanzania

Abstract

Magombera and Kimboza forests in Tanzania are small lowland fragments on the eastern foothills of the Udzungwa and Uluguru mountains, respectively. In July–August of 2023 and 2024, we conducted surveys of the forest birds in the forests, using mist nets, opportunistic observations and audio playback. We recorded 58 species in Magombera and 69 in Kimboza including 7 and 12 species new to the sites, respectively. This increases the total number of species to 71 in Magombera and 89 in Kimboza. The majority are widespread in forest habitats in Tanzania, and are either forest generalists or forest visitors, with the number of species belonging to these categories similar in the two forests. More than twice as many obligate forest specialists are known from Kimboza Forest, compared to Magombera Forest, including seven with their main distribution in the Eastern African coastal forests. We identify three possible explanations for these differences: less field work has been carried out in Magombera; differences in forest community structure and floristic composition; and distance from coastal forests. We also recorded more seasonal altitudinal migrants (species and individuals), from nearby mountain areas, in Kimboza relatively to Magombera. This difference is possibly due to the loss of lowland forest in the Uluguru Mountains where the migrants would ‘winter’ previously, whilst in the Udzungwas a continuous forest cover still exists down to 300 m, providing a lowland forest retreat for altitudinal migrants. Instead, migrants from the Ulugurus appear to have to move through at least 11 km of open land to isolated lowland forests in the foothills, such as Kimboza Forest.