The Impact of Forest Invasion in the Glades on Birds in Arusha National Park

This study was aimed at determining how growth of forest into man-made and natural glades affects bird species diversity, richness and evenness, and feeding guild composition in Arusha National Park, Tanzania. The fixed belt transect plot was used to survey bird species during the wet season. Fifty-eight bird species among 29 Families from 11 Orders were recorded. Passeriformes was the dominant Order for both glade types. The Shannon-Wiener Diversity Index was highest for man-made glades, as compared to that of natural glades (H'=3.677 and H'= 3.1, respectively). Student's t-test analysis of the means of bird diversity in forest transects and corresponding forest-invaded glade transects showed that there was no significant difference in bird species diversity between the two glade types (t = -3.4208, p = 0.07186). Manmade glades had a higher species richness than natural glades (Margalef's Richness Index R1=8.93 and R1=6.219, respectively) and this variation was statistically significant (Chi-square: χ2 = 4.5696, P = 0.033). Also, species evenness was higher in man-made glades than in natural glades (Pielou J=0.8069 and J=0.7627, respectively). The Sorensen Similarity Index analysis showed that bird species communities were similar (CC= 0.53), with insectivores being most dominant feeding guild for both glade types. Since the variety of bird species for forest-invaded man-made glades was richer and more even than for the natural glades, we conclude that re-clearing of forest invasion for man-made glades should proceed in order to generate these different unique microhabitats that are vital to the conservation of a wide variety of bird species. This is in contrast to not re-clearing forest invasion into man-made glades, where diverse microhabitats would not be generated or available to support increased bird species richness and evenness. Hence, maintenance of these unique microhabitats will promote less decline of bird diversity in Arusha National Park.