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Résumé :
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Of 69 reports of all-dark petrels in the North Atlantic, mostly since 1980, 22 have resulted in positive identification: 13 as Swinhoe's Storm-petrel Oceanodroma monorhis (14 individuals, all trapped) and nine as Bulwer's Petrel Bulweria bulwerii (ten birds). Many of the unidentified storm-petrels seem likely also to have been Swinhoe's, rather than the rare dark-rumped variant of Leach's Storm-petrel O. leucorhoa. It appears possible that this warm-water species entered the South Atlantic from its Indian Ocean wintering grounds, tried to migrate north and, moving into the North Atlantic, became trapped; general oceanographic conditions would assist passage of Swinhoe's around South Africa, and frequent influxes may have occurred. Although circumstantial evidence also suggests the possibility that the species may breed on the Selvagens (Madeira), this remains unproven. Accounts of larger unidentified petrels in the English Channel are similar to published descriptions of Matsudaira's Stormpetrel O. matsudairae; but they could also refer to Bulwer's Petrel showing a flight pattern poorly described or rarely seen, or, in one case, in moult. A great number of other records of similar birds strongly suggest Bulwer's Petrel, and these coincide with the occurrence of other warm-water species such as Cape Verde Petrel Pterodroma feae and Swinhoe's Stormpetrel. It seems possible that all the larger all-dark petrels observed in the northeast Atlantic were Bulwer's Petrels.
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