A small group of two all dark rather small species, superficially resembling dark Gadlfy Petrels or Strom Petrels.
- Bulwer's Petrel Bulweria bulwerii, Atlantic, Pacific and Indian Ocean.
- Jouanin's Petrel Bulweria fallax, northwestern Indian Ocean, breeding interior Oman.
Long time Bulweria petrels were considered to belong to the Gadfly Petrels, or at least very closely related to them, although some resemblances to the Shearwaters were also noted. Penhallurick and Wink (2004) found that, based on their genetic analysis, Bulweria is a sister clade to Procellaria that diverged about 32 mya from a common ancester.
Bulweria fallax has a limited distribution in the waters between eastern Africa and India, but is known to wander over huge distances, with records from Australia, Italy and Hawaii (Onley & Scofield 2007). It breeds in Yemen and Oman. The smaller bulwerii ranges in the tropical and subtropical zones of all three major oceans and breeds at many islands in the Atlantic and Pacific.
The flight of bulwerii resembles that of a large Storm Petrel: buoyant and erratic and close to water. In the larger fallax this is less pronounced and sometimes even languid with high arcs. Feeding is predominantly done by surface dipping, but bulwerii is known to make rather shallow dives, averaging 2.4 m +/- 1 m, to a maximum of 5.3 m (Mougin & Mougin 2000).
Bulwer's Petrel Bulweria bulwerii Deserta Grande, Atlantic Ocean
Culmen: 20.7 mm; Total: 53.5 mm, unsexed adult Courtesy of B. Zonfrillo, Univ. of Glasgow