Much of our basic information on the birds of Annobon comes from a visit to the island by C.H. Fry, in 1959, whose work also summarised previous data. In the last 40 years the only new information was obtained during a one-day visit in 1989, and some unpublished data on captured birds from 1987. According to this, Annobon holds 16 breeding birds, of which ten are terrestrial and six marine species. Another four species appear to be regular migrants.