Human-induced Disturbances Influence on Bird Communities of Coastal Forests in Eastern Tanzania

Abstract

Aims: To assess the influence of human-induced disturbances on bird communities. Study Design: Longitudinal study. Place and Duration of Study: Four forests; - Kion/Zaraninge, Kwamsisi/Kwahatibu, Msumbugwe and Gendagenda in Pangani–Saadani ecosystem, from October 2010 to January 2011. Methodology: Eight permanent transects, each 500 m long stratified into forest core and forest edge habitats were used in each forest to identify types and quantify levels of human-induced disturbances, determine bird species composition, diversity and richness, and abundance. Therefore three circular plots, each 20 m radius were allocated at beginning, middle and end of each transect. The level of disturbance was assessed using four disturbance indicators; tree lopping, human trails, Pit-sawing and animal snaring while bird species were identified by sight and call. One-way Analysis of Variance was used to test for differences in bird abundance between forests. Moreover, Shannon-Wiener Diversity Index (H’) was calculated for each forest to assess species diversity and evenness, and Bray-Curtis Cluster analysis was used to determine similarity in bird species composition between the forests. Results: A total of 564 individuals composed of 88 bird species distributed in ten Orders were recorded. The level of Pit-sawing and lopping differed significantly between forests (P<.05) with Msumbugwe being more disturbed than the rest. Bird abundance differed significantly between the forests (P<.05) with the highest abundance occurring in Msumbugwe. As expected, species richness and diversity were greater in least disturbed forests-Kiono/Zaraninge and Kwamsisi/Kwahatibu than in the highly disturbed forest, but forest dependent species were not significantly different between the study forests. Apparently, only Pit-sawing was found to correlate with bird abundance (P<.01) whereas similarities in species composition were evident with Kion/Zaraninge and Gendagenda exhibiting much overlap. Conclusion: Increasing forest disturbances seems to negatively impact on distribution of birds thus challenging conservationists to devising sustainable forest management strategies in order to sustain bird diversity and abundances in these unique forests.