Genus Pterodroma, Pseudobulweria and Aphrodroma are also knwon as the Gadfly Petrels. They vary in size from rather small birds such as the Cookilaria-species, measuring about 26 cm, to the much larger and robust representatives of this group like the White-headed Petrel with an overall length of about 43 cm. Their plumages also vary a great deal from species to species; from completely black to light grey mantles and pure white bellies, and with different color phases within species. One feature shared by all of them is the black bill of which the shape also shows much variation. Some species are extremely rare and restricted to a very limited area, other are abundant and wander widely or have unknown pelagic ranges.
The group of the Gadfly Petrels counts over 35 species, mainly from the Southern Hemisphere. There are three genera: Pterodroma with about 30 species, Pseudobulweria counting four and Aphrodroma with only one. Many authors have tried to classify the large number of species of this group and to determine their relationships. This has resulted in a division in several subgenera and the grouping of several species which are considered to have a more or less close relationship. The taxonomic discussion has not come to an end yet: new species have been added or split recently and probably will be in the near future.
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Video Tahiti Petrel
copyright: Keith Blomerley
In the Marquesas and Society Islands, rat predation is an observed but unquantified problem. It is likely to have coexisted with black rats Rattus rattus for decades and they perhaps do not pose a major threat. Young birds are also attracted by lights at night, mainly on Tahiti in the urban areas around Papeete and in New Caledonia around Noumea, rural villages and active mining sites. Electric powerlines in the mountains of French Polynesia may also be a problem. On Grand Terre, wild pigs, feral cats and dogs, and rats Rattus spp. may pose a threat to remaining colonies (although rats have been eradicated from all islets in the southern lagoon).The newly discovered sites in New Caledonia are all in areas threatened by nickel mining. In colonies where the soil is deep enough for Wedge-tailed Shearwaters to nest there can be intense competition for burrows. Local people are known to take birds to use their white feathers for fishing lures.