Effect of a road on avian diversity in the Kalahari woodland

Roads may have negative or positive effects on wildlife. I surveyed birds along a c. 21 km transect alongside a road from Katima Mulilo to Ngoma bridge in the Zambezi Region, north-eastern Namibia, and on a second transect (control) parallel to the first one and 200–400 m away from the road. The habitat is Kalahari Woodland, partly transformed to cultivated fields. The number of bird species was similar on both transects (56 vs. 48 species; x2 = 0.62, p > 0.05), but the number of breeding pairs (overall population density) was much higher away from the road than close to it (409 vs. 283 pairs; x2 = 22.9, p < 0.01). The Shannon’s Diversity Index was very similar, while Pielou’s Evenness Index was identical in both transects compared. Five species (Blue Waxbill, Burchell’s Starling, Cape Turtle Dove, Fork-tailed Drongo and Grey-headed Sparrow) were dominant on both transects, while the African Grey Hornbill was dominant only on the transect away from the road, whereas the Red-billed Hornbill and Grey Go-away-bird were dominant only close to the road. Four species (African Grey Hornbill, Cape Turtle Dove, Meyer’s Parrot and White-browed Scrub Robin) had population densities significantly higher on the transect away from the road than close to it. However, population densities of nine other species did not differ significantly between the two transects. In general, the avian communities along and away from the road were similar, probably because traffic volume was rather low and the land cover on both transects was similar in terms of natural vegetation and degree of transformation.