Procellariiformes

They are all highly pelagic seabirds, and all of them have their nostrils enclosed in one or two tubes on their straight, deeply grooved bills with hooked tips. The beaks are made up from several plates. Wings are long and narrow; feet are webbed, and the hind toe is undeveloped or non-existant. Plumage is predominantly black or gray.

The tubes may be used to smell, to spread stomach oil, or to excrete salt.

The longer-winged species fly using a switchback technique to minimise active flapping. All eat fish, squid or similar marine prey.

Most are almost unable to walk on land, and many species visit their remote breeding islands only at night. The exceptions are the huge albatrosses, and the fulmars. The latter can disable even large predatory birds with their obnoxious stomach oil, which they can project some distance.

There are a total of 93 species of Procellariiformes world-wide, divided among four families:

• Procellariidae (shearwaters, fulmars, petrels, and prions)
• Diomedeidae (albatrosses)
• Hydrobatidae (storm-petrels)
• Pelecanoididae (diving petrels)

Procellariiformes are most closely related to Sphenisciformes (Penguins).

In the Sibley-Ahlquist taxonomy, the tubenoses are included in a greatly enlarged order Ciconiiformes.