The mountains of south-eastern Nigeria are a western extension of the Cameroon mountain range, which is classified as an endemic bird area (EBA). Unlike its eastern extension in Cameroon, most of the ornithological surveys in the western extension of the Cameroon highlands in Nigeria have produced only limited checklists and inventories. There is a clear need for quantitative baseline data so that conservation problems can be identified. Twenty line transects covering a total transect length of 28.8 km were used to survey five sites (Afi Mountain Wildlife Sanctuary, Oban Division and Okwangwo Division of Cross River National Park, Sankwala Mountains and Mbe Mountains) in the westernmost extension of the Cameroon Mountains EBA in south-eastern Nigeria. Vegetation measurements were taken to control for the potential confounding effect of variation in vegetation density and structure on detectability of birds between sites. The 193 bird species recorded in Afi, 158 in Sankwala, 124 in Oban, 100 in Mbe and 73 in Okwangwo Division included most of the Cameroon highlands restricted range species. The results show that the mountains of south-eastern Nigeria are important parts of the Cameroon EBA, particularly Afi Mountain Wildlife Sanctuary. However these sites are threatened by fire and livestock grazing on the hilltops, shifting agriculture on the hillsides and lowlands, and logging for timber in some parts, as well as wildlife hunting for bushmeat.