This IBA includes the marine area adjacent to the Desertas island terrestrial IBA (PT085) and comprises three uninhabited volcanic islands: Ilhéu Chão, Deserta Grande and Bugio. Deserta Grande is the largest, but it is in Bugio that breeds the only colony of Fea's Petrel known in Europe, with a population of less than 200 pairs. Ilhéu Chão, located north of those two, is the smallest and lowest of the three, and has a colony of Yellow-legged gulls with around 700 pairs. The Desertas hold some of the most important colonies of seabirds in the Atlantic, with large populations of Procellariiforms and the only European population of Fea's Petrel. It is also one of the most important areas for the reproduction of the monk-seal Monachus monachus in Europe (Neves and Pires 1999). The marine IBA include areas that are used by the pole and line tuna fishing fleet to fish for live bait.
Fea's Petrel Pterodroma faea: The only colony of Fea's Petrel known in Europe breeds on Bugio, with approximately 160-180 pairs. Elsewhere in the world, only the archipelago of Cape Verde has other colonies, although recent studies indicate significant differences between these populations, which may give rise to a split into two distinct species (Jesus et al. in press). Cory's Shearwater Calonectris diomedea: Previously used as a feeding resource by the local populations, the creation of the Ilhas Desertas Nature Reserve in 1986 granted this species a larger degree of protection. This protection may have contributed to underestimate the current population. The regularity with which this IBA is used was demonstrated by the use of data-loggers, both during the incubation period and during chick-rearing. Little Shearwater Puffinus assimilis: A less abundant species with inaccessible colonies on the Desertas, making monitoring difficult. May be found near the colonies all year round, especially from December to April. Bulwer's Petrel Bulweria bulwerii: The population on the Desertas is estimated at 1,500 pairs, the largest colony in the Atlantic. It can be found in this region between March and October. Madeiran Storm-petrel Oceanodroma castro: There are both "cold-season" and "hot-season" populations on the Desertas. Around 1,000 breeding pairs are estimated, although more recent estimates indicate likely populations of more than 10,000 birds for the Madeira archipelago, concentrated mostly on the Desertas and Selvagens. Yellow-legged Gull Larus cachinnans: Present all year round, breeds on all three islands, although the largest colony is on Iléu Chão, the northernmost island. Its population on the Desertas is estimated at over 700 pairs. Common Tern Sterna hirundo: Some tens of pairs breed around these islands. Other species observed in this IBA: Fea's Petrel, White-faced Storm-petrel.
BirdLife International (2022) Important Bird Areas factsheet: Desertas. Downloaded from http://www.birdlife.org on 10/12/2022.