São Tomé and Príncipe contain 28 species of bird that are endemic to one or both of the islands. These include 21 single island endemics, 15 on São Tomé and 6 on Príncipe with a further 5 being found on both islands. Two monospecific genera are endemic to São Tomé, Amaurocichla and Neospiza, and one to Príncipe, Horizorhinus. The taxonomy of some of the endemic species and sub-species is unclear. Sibley and Monroe (1990) classify the two Alcedo kingfishers as full species. Other authors regard them as subspecific forms only and we follow that treatment here. There seems little justification for retaining the monospecific genera Thomasophantes and Dreptes and in most treatments they are subsumed within Ploceus and Nectarinia respectively.

Of the mainland African species represented on the islands, eleven have developed subspecies. In addition, a possibly undescribed subspecies of the Maderian Petrel Oceanodroma castro may breed on offshore islets (Harris 1969).

The level of endemism is high on the islands with over half of the breeding landbirds either being an endemic species or subspecies.On São Tomé 57% (28 out of 49) of the breeding landbirds are either endemic species or subspecies. For Príncipe the level of endemism is similar with 54% (19 out of 35) of the resident landbirds being endemic species or subspecies.

Collar and Stuart (1988) ranked the rainforests of south-western and central São Tomé second in a list of 75 of the most important forests for conservation in tropical Africa, mainly due to their high threatened species score. More recently both islands have been designated as individual Endemic Bird Areas (EBAs) (ICBP 1992). The importance of these two EBAs is such that they are rated as Critical. This rating is based upon the highest restricted-range bird species richness score, with both islands being three times or more richer in species than expected for their area. The rating also takes account of the degree of threat to the EBA. Both EBAs score the highest rating, with less than 5% of the area of each EBA being found in protected areas. Finally the degree of threat to birds is rated as Medium (Birdlife International 1992) although this must be revised in the light of the development plans for Príncipe.