Pelecanoididae

The diving petrels are a family of small seabirds comprising four species in a single genus Pelecanoides. The most widespread, Common Diving Petrel (P. urinatrix) has six subspecies, some of which may represent cryptic species. All species are very similar in shape but separated by slight plumage differences and, more importantly, by bill morphology. 

Additional information

Like petrels and shearwaters, they have a hooked bill with tube nostrils on the culmen ridge; however, the tube opens upward rather than forward. The feet are webbed, and the legs are laterally compressed and placed far back on the body. While this position facilitates swimming and diving, it makes the birds awkward on land; they usually move by 'tobogganing' on their belly, pushing themselves along with their wings. They have to patter along the water surface, into the wind, to get airborne, and ground landings are clumsy. The birds also have gular skin that can expand to form a pouch, which the birds use to carry food to their young.

Diving petrels come ashore only to breed. They are gregarious at their breeding colonies, but at sea are generally solitary or found in small groups. The flight is fast, with steady wing beats, reminiscent of auks, and the birds' strong wings enable them to literally fly through waves. When pursuing prey, they dive from flight or from the surface, they 'fly' underwater to more than 64m.

The nest, dug by both members of the pair, comprises a short burrow and a chamber lined with feathers, vegetation, or small stones. The entrance is camouflaged with vegetation.

Taxonomy 

There are four species, all belong to one genus, Pelecanoides.

• P. georgicus (South Georgia Diving Petrel)
• P. urinatrix (Common Diving Petrel)
• P. garnotii (Peruvian Diving Petrel)
• P. magellani (Magellanic Diving Petrel)

Although some studies suggest including the diving petrels in family Procellariidae (petrels and shearwaters), the body shape is very different: more similar to some auks (family Alcidae)