Species richness and relative abundance of montane forest birds in the Udzungwa Mountains are presented for the 11 forests larger than 1 km2. A high positive correlation between the number of montane bird species and the size of the forest is found with the highest species richness recorded in the largest forest. A few small (< 5 km²) forest fragments also support a high richness of forest birds. Their isolation from larger forest tracts is probably relatively recent (within the last 100-200 years) and their high bird species numbers may be partly due to delayed extirpations. Twenty-three restricted range montane forest species were recorded, and many of these were widespread in the Udzungwas. The largest populations of White-winged Apalis Apalis chariessa, Dapple-throat Arcanator orostruthus, Iringa Akalat Sheppardia lowei and Usambara Weaver Ploceus nicolli are most likely in Udzungwa forests.