Desertas Petrel (Pterodroma deserta)

[order] PROCELLARIIFORMES | [family] Procellariidae | [latin] Pterodroma deserta | [authority] Linnaeus, 1758 | [UK] Desertas Petrel | [FR] Calliste tiquete | [DE] Kapverdensturmvogel | [ES] Petrel Gon-gon | [NL] Cape Verde Stormvogeltje

Subspecies

Genus

Physical charateristics

slightly larger than Manx Shearwater, with proportionately shorter but much heavier bill, larger head, more-angled and -pointed wings, and narrower tail. In contrast to dusky-grey saddle and pale-grey tail, grey cap with dark eye patch and long M-shaped pattern across grey-brown wings and dark rump form striking pattern. Mainly sooty underwing shows indistinct greyish panel along centre; shows only dusky shawl or breast side on otherwise white underbody. At some angles, dark eye patch emphasized by extension of white forehead backwards to over eye.
Needs to be distinguished from Zino’s Petrel (present within range of Fea’s Petrel) and Soft-plumaged Petrel (vagrant from southern oceans); see those species. Note that vagrants to European waters considered more likely to be this form or southern Soft-plumaged Petrel than extremely rare Zino’s Petrel. Much smaller (by fully one-third) than Fulmar, which also lacks dark head and (in pale birds) dark underwing.
Flight like other gadfly petrels, with dashing, towering, and careening actions all well developed in higher winds. Indulges in remarkable side to side looping manoeuvres, unlike other tubenoses. Does not shun coast and occasionally follows ships.

Range

Atlantic Ocean : Desertas Islands

Habitat

On the Desertas, Fea’s Petrel breeds in areas where there is a thick layer of earth covered with grass and Mesembryanthemum. On and around the southern plateau of Bugio there are places with earth more than 1 m thick, and it is essential that a sufficient depth is available for the birds to construct burrows.

Reproduction

On Bugio, the birds return to their breeding grounds at about the end of June and laying starts about 20 July, with breeding activity reaching its peak during early August. Birds enter the breeding sites after dark and call loudly if there is no moon, falling silent when the moon rises. The nesting burrows have varying entrance sizes and depths: the majority are more than 1 m in length and with an elbow, the nest-chamber being 30-60 cm below the surface.

Feeding habits

The species is essentially pelagic and highly adapted for living out of contact with land. Food is likely to consist of fish, cephalopods and crustaceans, often as plankton, but there is very little specific information available on diet and feeding behaviour. The birds can often be seen from the shore by day, flying and sometimes feeding.

Conservation

This species has a large range, with an estimated global Extent of Occurrence of 370,000 km2. The global population size has not been quantified, but it is believed to be large as the species is described as ‘frequent’ in at least parts of its range (Stotz et al. 1996). Global population trends have not been quantified, but the species is not believed to approach the thresholds for the population decline criterion of the IUCN Red List (i.e. declining more than 30% in ten years or three generations). For these reasons, the species is evaluated as Least Concern.
The only known place in Europe where Fea’s Petrel breeds is on Bugio, southernmost island of the Desertas. The majority of burrows are to be found on the southern plateau, despite the fact that the northern plateau is more extensive, though more arid and with less vegetation. On the basis of sub-fossil Pterodroma bones, the species is believed formerly to have bred on Deserta Grande, Porto Santo and the main island of Madeira. It seems increasingly likely that it breeds in the Azores. Outside Europe it breeds in the Cape Verde Islands, where the population is believed to be of 1,000 breeding birds or roughly 500 pairs. The population on Bugio is considered to be around 150-200 breeding pairs and appears to be stable. Not much is known about the population on the Cape Verde Islands, though there are estimates of a total population of up to 1,000 breeding pairs. In the Madeira archipelago it nests only on Bugio, and the greatest concentration is on the southern plateau of this island. A few nest on the northern plateau, but, as this is not accessible by foot and extremely difficult to reach even by helicopter, that area is almost impossible to study.

Over the years the birds have suffered predation by fishermen, but since the whole land surface of the Desertas were made a strict reserve this situation has improved dramatically.

Migration

Fea’s Petrel Pterodroma feae is an extremely rare and threatened Macaronesian endemic petrel, known to exist only on Bugio and some of the Cape Verde Islands. Resident.

Distribution map