Spatial response of the globally-endangered Sokoke Pipit (Anthus sokokensis van Someren, 1921) to habitat modification in an Eastern Arc Coastal Forest

Abstract

The Arabuko-Sokoke forest is the largest relic of a formerly larger contiguous East African coastal forest. It forms part of the Eastern Arc Forest system which is a global biodiversity hotspot with considerable species endemism. As one of the most important bird habitats in Africa, it hosts nine globally-threatened and four regionally threatened species. Despite such conservation significance, the forest is undergoing rapid modification and habitat loss mainly from anthropogenic pressures, with negative impacts on sensitive species such as the Sokoke Pipit (Anthus sokokensis). This study examined impacts of change in habitat quality on the species’ population and spatial occurrence within three blocks of Brachystegia woodland in the forest. Over a three week period, six 1-km transects were used to estimate the species’ population in relation to major habitat quality variables. Sokoke Pipits occurred at an overall mean density of 0.72±0.15 birds/ha with an estimated population of 5,544 in the Brachystegia woodland. Tree logging intensity was the key cause of the degradation of the Sokoke Pipit’s critical habitat, which affected its density (R2 = 0.663, ß = -0.814, p = 0.048). The species also preferred sites covered with deep floor litter (R2 = 0.769, ß = 0.877, p = 0.021) even in areas with low tree canopy height, but showed no clumped distribution (χ2(2, 0.05) = 2.061). Sites with intensive elephant activity, which leads to tree felling and clearing of the understorey, had low Sokoke Pipit densities. We conclude that  although human-driven tree removal is a major driver of degradation of the Sokoke Pipit’s critical habitat, elephant activity may be an important additional factor in this process. Long term conservation strategies for the species will require stricter control of logging but management of the population and dispersal of elephants across the forest, especially in Brachystegia woodland, may also be helpful.