Seasonal changes in avian assemblages in kaokoland (mopane) savanna in the ogongo game reserve, north-central Namibia

Abstract

Studies were conducted at UNAM Game Reserve (c. 1000 ha) in the BIOTA Observatory ’Ogongo’, which is located c. 50 km NW of Oshakati, north-central Namibia (17 700S, 15 310E). The natural vegetation of this area is the Koakoland (Mopane) Savanna. In 2011-2012, the line transect method has been employed to assess the species composition, dominance structure, and relative abundance of all bird species, and their seasonal changes in the late rainy season (March), middle of dry season (July), and beginning of rainy season (November). In total, 66 resident (46 in late rainy season, only 35 in the middle of dry season and 39 at the beginning of rainy season) and 19 non-resident species were recorded. Only two resident species have been classified as dominants in all three seasons: Plocepasser mahali and Uraeginthus angolensis; five species were dominants in two, and four species in one season. The avian assemblage undergoes significant seasonal changes, mostly related to the water regime in oshanas. Although the number and proportion of dominant species changed only slightly from season to season (6-7 species; 58.8-62.4% of contribution), highly significant seasonal differences in abundance were recorded for 18 resident species. Clear seasonal changes were also found in the proportions of main feeding guilds, i.e. granivores and insectivores. In comparison with other habitats in Namibia, Ogongo Game Reserve has a rich and diverse avifauna. For many bird species the reserve constitutes a safe breeding habitat, and a rich feeding area. It is fully justified to retain its status as nature sanctuary in Cuvelai Drainage ecosystem.