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.
Highlights
Tropical forests constitute the most important habitats for biodiversity because despite covering less than 7% of the global land surface, they host at least half of all terrestrial species on earth[1]
Birds are among the most affected by forest destruction and habitat loss, forest-dependent species[3,4] which may respond to such perturbations in such spatially distinct patterns as to make them suitable for monitoring the quality of the forest habitat and its suitability for other taxa[5]
Sokoke Pipit[6] is a forest-floor insectivore of the East African coastal forests of Kenya and Tanzania[7,8,9]. This globally-endangered species[10] is generally restricted to the woodland habitat dominated by Brachystegia tree species (Leguminoceae)[9,11] where it feeds on arthropods on the ground or in the understorey[9,12,13,14]
Summary
Tropical forests constitute the most important habitats for biodiversity because despite covering less than 7% of the global land surface, they host at least half of all terrestrial species on earth[1]. Sokoke Pipit[6] is a forest-floor insectivore of the East African coastal forests of Kenya and Tanzania[7,8,9] This globally-endangered species[10] is generally restricted to the woodland habitat dominated by Brachystegia tree species (Leguminoceae)[9,11] where it feeds on arthropods on the ground or in the understorey[9,12,13,14]. Would be helpful – and especially why these and other aspects render the Pipit a good indicator species/proxy for habitat condition This could be revisited in the Discussion as links are made between habitat conditions and occurrence of the bird (where you discuss the underlying mechanisms for why it thrives in some parts of ASF and not others, and why it’s abundance correlate strongly with some types of disturbance and not others). We have clarified that our study, in contrast to that of Musila et al which examined species’ response to habitat change, dealt with spatial variations in habitat structural quality, and that the results provide an update in the spatial and temporal dimensions of the habitat effects on the species
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