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 Mountains and Coastal forest ecoregion which is a global biodiversity hotspot with considerable species endemism. 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), one of the globally-endangered birds. The study examined impacts of habitat degradation on the species’ population and spatial occurrence within three blocks of Brachystegia woodland in this forest. Over a three week period, six 1km 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). The species generally occurred at very low densities in sites with intensive elephant activity that accelerated habitat modification by felling trees and opening the understorey. We conclude that although human-driven tree removal is a major driver of overall degradation of the Sokoke Pipit’s critical habitat, elephant activity may be an important additional catalytic factor in this process. Long term conservation strategies for the species will require stricter control of logging. Management of the population and dispersal of the elephants across the forest, especially in the Brachystegia woodland, may also be helpful.
Highlights
Tropical forests are the most important habitats for biodiversity because they cover less than 7% of the global land surface, they host at least half of all terrestrial species[1]
The Sokoke Pipit[6] is a forest-floor insectivore of the East African Coastal forests of Kenya and Tanzania[7,8]. This globally-endangered species[10] is generally restricted to near-closed canopy woodland habitat dominated by Brachystegia tree species (Leguminoceae)[11], where it feeds on arthropods on the ground or in the lower understorey[12,13,14], in parts of the woodland with deep floor litter cover[14]
Musila et al observed that the Sokoke Pipit prefers the thicker areas of the understorey, with most of the time spent less than 2 m above ground when not feeding, quickly flushing to upper branches when threatened before returning to forage on the forest floor
Summary
Tropical forests are the most important habitats for biodiversity because they cover less than 7% of the global land surface, they host at least half of all terrestrial species[1]. The Sokoke Pipit[6] is a forest-floor insectivore of the East African Coastal forests of Kenya and Tanzania[7,8] This globally-endangered species[10] is generally restricted to near-closed canopy woodland habitat dominated by Brachystegia tree species (Leguminoceae)[11], where it feeds on arthropods on the ground or in the lower understorey[12,13,14], in parts of the woodland with deep floor litter cover[14]. You reference other studies that have explored other species in ASF and forest disturbance, but do not really explicitly state why the Pipit is a important indicator of forest condition. 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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