AVIAN SPECIES DIVERSITY AND DISTRIBUTION IN AND AROUND NORTH NANDI FOREST, KENYA

Abstract

Species-rich tropical forests are becoming increasingly fragmented, degraded, and declining in size threatening the survival of avian species that depend on them. Yet, avian species diversity and distribution in fragmented forests remain relatively unknown. This study was conducted between January 2015 and June 2015 in and around North Nandi Forest. The main aim of the study was to assess avian species diversity and distribution in four habitats; indigenous forest, disturbed forest, plantation forest and farmland. Birds were surveyed using point counts, timed species counts; distance line transects and mist nets. Shannon-Weiner diversity index H’ for bird community ranged from 3.060 for plantation forest to 4.053 in disturbed forest. Bird species richness was significantly different in the four habitats surveyed (χ2=26.747, df=3, P<0.0001). There was also significant difference in bird abundance across the four habitats (ANOVA; F=15.141, df=3, 1121, P<0.0001). Results on distribution of bird feeding guilds revealed a significant difference in abundance across the four habitats for insectivores (F=3.090, df=3, 297, P<0.0001) and granivores (F=10.496, df=3, 297, P<0.0001). The abundance of frugivores, raptors, nectarivores and omnivores showed no significant difference across the four habitats (P>0.05 in all cases). PCA multivariate analysis revealed that two variables; diameter at breast height and ground cover with eigen values >1 were strongly correlated with habitat structure in all the four habitats and explained 73.2% of the total variance. Linear regression analysis revealed a significant difference between bird species richness and tree diameter at breast height (F=99.760, r2=0.73, df=1, 1268, P<0.0001) and tree height (F=97.134, r2=0.71, df=1, 1268, P<0.0001). Bird abundance also revealed a significant difference with diameter at breast height (F=77.654, r2=0.58, df=1, 1268, P<0.0001) and tree height (F=68.163, r2=0.51, df=1, 1268, P<0.0001). Habitat destruction (70%) was the main detrimental human activity on the avifaunal habitats while subsistence hunting of birds (10%) only directly affected certain bird species. The middle age bracket (20-40 years) visited the forest most frequently (χ2=19.485, df=4, P=0.001), males were mainly involved in timber extraction and livestock grazing as opposed to females took part in firewood and medicinal herbs collection. Conservation efforts of forest birds should focus on maintaining large forest patches while in farmlands, bird conservation should focus on maintaining extensive environmental-friendly farming systems that promote sustainable agricultural development in North Nandi Forest and its surroundings.