Yelkouan shearwater Menorca. A study of these birds recommended that a combination of morphological characteristics and DNA sequence data should be required at least for scientific purposes to assign individual birds to either species. It was formerly considered a subspecies of the Manx shearwater (see there for more on the "Puffinus puffinus" superspecies). After the first split, it was the nominate subspecies of the so-called "Mediterranean shearwater" for nearly ten more years; it is considered a monotypic species now, as the Balearic form "mauretanicus" has been separated as the Balearic shearwater. The yelkouan shearwater appears to belong to a group of Mediterranean
Bulweria "b" sequence analysis has proven them to be closely related to the shearwaters in the genus "Puffinus" and especially the "Procellaria" petrels. Bulweria Bulweria is a genus of seabirds in the family Procellariidae named after English naturalist James Bulwer. The genus has two extant species, Bulwer's petrel ("B. bulwerii") and Jouanin's petrel ("B. fallax"). A third species, the Olson's petrel ("Bulweria bifax"), became extinct in the early 16th century; it is known only from skeletal remains. Bulwer's Petrel ranges in the Atlantic, Indian and Pacific Oceans, whereas Joaunin's Petrel is confined to the northwestern Indian Ocean. Olson's Petrel is known