Effects of habitat structure and altitudinal gradients on avian species diversity at Kurra Falls Forest, Nigeria

Abstract

All bird species are restricted to varying degrees in the range of habitats they occupy. They share at least a portion of their habitat ranges, but between habitats in a local or regional landscape mosaic, some species are replaced by others as the habitat-type or structure changes. This study was carried out at Kurra Falls Forest. The forest is a typical savanna woodlands interspersed with gallery forests, patches of grasslands, and rocky outcrops. The forest is also characterised by altitudinal gradients with elevations. Using line transect methods, the effect of habitat structure and altitudinal gradients on bird species diversity at Kurra Falls Forest were studied. A total of 175 bird species were recorded, two of which are among the four endemic birds to Nigeria. Tree height, tree number, and canopy cover together had a significant effect on bird species diversity. Bird species diversity increased with increase in tree height. A significant decline in bird species diversity with increased number of trees and canopy cover was noted. This result probably suggests an accumulation of forest edge species and generalist species in the less forested habitat. Few forest species inhabited the forest interior where high number of trees and low visible sky can be found. It is also possible that the dominant species of the forest interior might have out compete the subordinate forest interior species. In addition, species diversity did not significantly vary with altitude.

Keywords: birds, diversity, habitat structure, altitude.