Density and population estimates of Amani Sunbird Anthreptes pallidigaster in Kenya's Arabuko-Sokoke Forest

Abstract

The Arabuko-Sokoke Forest (ASF) is the largest area of coastal forest remaining in East Africa. However, encroachment and habitat degradation threaten the existence of many plant and animal species, including the East African endemic Amani Sunbird Anthreptes pallidigaster. The aim of this study was to arrive at an estimate of population size for Amani Sunbirds within the ASF. Forty transects were surveyed over 3 months in 1999. The total length of all transects was 63.572 km. In total, 103 Amani Sunbirds were detected at an estimated density of 36.6 birds/km². Thus with a total area of 77 km², the Brachystegia woodland of the ASF should hold about 2,818 Amani Sunbirds. This estimate is much lower than the 5,800–9,400 birds estimated by Britton and Britton (1978). While it is possible that their estimate was inaccurate, the apparent decline in the population could be due to natural population fluctuations. Habitat degradation is another possible cause, as illegal logging and tree-felling continue in and around the ASF. Since the majority of the local people around the ASF are farmers, there is little concern for the welfare of the forest, especially when they see few benefits stemming from conserving the resource. Future funding towards the conservation of the ASF should focus on (1) setting up a consistent monitoring programme that will provide further population estimates for endangered species such as Amani Sunbird, and (2) ensuring that local people get some benefit.