Avian communities along a disturbance gradient in and around Budongo Forest Reserve, Western Uganda

Abstract

The natural forests which are the main sources of biodiversity are cleared and replaced with commercial Pine plantations to provide wood resources for the growing population and creation of fragments. This sets in an ecological argument to whether the forest fragments and forest plantations can complement continuous forests in supporting bird life. Therefore, this study aimed at assessing bird assemblage in the three habitat types in and outside Budongo forest reserve. Birds were sampled using fixed width point counts along transects and habitat characteristics such as number of fruiting trees, number of snags and height of dominant trees were sampled in plots along the transects. Bird diversity indices were computed and compared among the habitat types using linear models. Linear models were also used to test the influence of habitat characteristics on bird diversity indices. Non-metric multidimensional scaling ordination was used to visualize bird species composition among the three habitat types. Differences in bird assemblage composition between habitats were tested by Permutational Multivariate Analysis of Variance procedure and a Similarity Percentage test was conducted to estimate overall dissimilarity among habitat types. In total, 128 bird species belonging to 49 families were recorded across the three habitats. Overall bird abundance and richness were highest in the continuous forest and lowest in the plantation. Evenness and Shannon-Weiner diversity were higher in the fragment and lower in the plantation. There was a variation in the habitat characteristics and their effects on species diversity as abundance increased with number of snags and Shannon-Weiner declined, evenness declined with increase in tree height. Species composition were considerably different in the habitats. Functional traits of birds varied too where; frugivores and nectarivores were dominant in the fragment and fewer in the plantation. Forest specialists and generalists dominated in the continuous forest and were lower in the plantation. Results have shown that these forest fragments and plantations are important for supporting bird life and can complement continuous forests. Therefore, efforts should be taken to protect the remaining forest fragments both the micro and macro niches for their uniqueness in supporting species diversity.