Restricted nesting habitat and reproductive failure of Magnificent Frigatebirds Fregata magnificens in the Cape Verde Islands

The islets of Baluarte and Curral Velho, off the island of Boavista, Cape Verde Islands, are the only two breeding sites of the Magnificent Frigatebird Fregata magnificens in the Western Palaearctic. This East Atlantic relict population was monitored from the summer of 1999 up to May 2006. Most surveys were conducted during the breeding season, i.e. from November to June. Total reproductive failure has been the rule over the last seven consecutive breeding seasons. Possible causes of nest failure are attributed to: 1) accidental egg loss during the incubation period; 2) hatching failure. The most plausible reasons explaining both causes are discussed. Human persecution and disturbance, restricted nesting habitat and isolation, and unsuccessful breeding has brought the population on the verge of extinction. The remaining population, thought to consist of 4-5 adult individuals (2 females and 2-3 males), is unlikely to survive on its own.