Habitat use and implications for avian species in Sambisa game reserve, Borno state, Nigeria
The study determined the effect of vegetation physical structure on avian species diversity and abundance in Sambisa Game Reserve in Borno State, Sudano-Sahelian vegetation. Bird species were observed, identified, counted and the associated vegetation variables were estimated in a 64 1000-m-long transects, 3 surveys per transect, from 2011 to 2012. The vegetation variables were lumped into various principal components (PCs) with principal component analysis (PCA), but only the first principal component (PC1) with the highest variance (25.15 %) and characteristics of complex vegetation, named vegetation physical structure complexity, was used in the regression analysis. A positive linear relationship existed between PC1 and bird species diversity indices (F1, 165 = 51.54, P < 0.001 for Shannon Wiener bird species index and F7, 187 = 59.69, P < 0.001 for bird species richness). Feeding guild abundances (Insectivores, Frugivores, Raptors and Nectarivores) showed positive relationship with the PC1 but granivore abundance showed a negative relationship with PC1. The PC1 probably played the most important role in the pattern of bird diversity and abundance in the Reserve. Increasing bird diversity and abundance across the complexity gradient was probably accommodated by increasing potential food and protection resources. If the logging activities in the Reserve are not properly checked, there will be serious threats of bird population decline and bird species loss, especially, insectivores, due to their high dependence on high trees with dense undergrowth. However, granivore population will build up and pose threats to the Reserve host communities’ farmed cereal crops.
Key words: Bird diversity; habitat loss, vegetation, Sambisa Game Reserve