Procellariiformes

Procellariiformes is an order of seabirds that live almost exclusively in the open ocean.

These birds are often called tubenoses in English. This name comes from their unique naricorns, which are bony nostrils. These nostrils are enclosed in tubes on their deeply-grooved bills. This order includes 147 living species found in oceans across the entire world.

They are most diverse in the seas surrounding New Zealand. Many species are colonial and nest on remote, predator-free islands. Larger species usually nest on the surface of the ground. Smaller species often nest in natural cavities or underground burrows.

These birds have specialized biological mechanisms to survive in salty environments. Because they drink seawater, they must excrete excess salt to stay hydrated. They possess an active salt gland located at the base of the bill. This gland removes salt from the system by using high levels of sodium ion reabsorption. This process happens within the kidneys to move sodium into the blood plasma. The salt gland then secretes sodium chloride using less water than was originally absorbed. This creates a 5 percent saline solution that drips from the nostrils.

This highly efficient system essentially generates salt-free water for the bird's physiological needs.

Procellariiformes also use unique methods to manage energy and defense. Most members, except for giant petrels, have weak legs and struggle on land. Many species only visit their breeding islands at night to avoid danger. Some birds, like the fulmar, produce a thick substance called stomach oil. This oil is a digestive residue stored in the proventriculus. It serves two main purposes: storing energy-rich food for long flights and acting as a defense. The fulmar can project this obnoxious oil some distance to disable large predatory birds.

The order is divided into four distinct living families. The Diomedeidae, or albatrosses, are very large birds with strong, hooked bills. They have strong legs that allow them to walk well on land. The Oceanitidae, or austral storm petrels, are among the smallest seabirds. They have a fluttering flight style and long but weak legs. The Hydrobatidae, or northern storm petrels, have longer and more pointed wings. Most species in this family have forked tails. Finally, the Procellariidae include shearwaters and giant petrels. They are often heavy for their size and must fly fast due to high wing loading.

Scientific understanding of these birds has changed through many discoveries. The order was named in 1888 by the German anatomist Max Fürbringer. His name comes from the Latin word *procella*, meaning a violent storm. Historically, the classification of these birds was often different. For example, the Sibley-Ahlquist taxonomy incorrectly placed them in the order Ciconiiformes. Modern genetic studies have since proven that Procellariiformes are a monophyletic group. This means they are a natural grouping that shares a common ancestor.

Recent phylogenetic studies have clarified how these birds relate to others. Scientists have found that procellariiforms are most closely related to penguins. The two groups diverged from a common ancestor about 60 million years ago. Genetic data also helped reorganize the storm petrels. Previously, all storm petrels were in the family Hydrobatidae. However, researchers found that these birds consisted of two deeply divergent clades. This led to the creation of the new family Oceanitidae in 2018 for the austral storm petrels.

These birds exhibit remarkable lifespans and complex social behaviors. They are monogamous and form long-term pair bonds that can last a lifetime. Most species lay only one egg per nesting attempt each year. Large albatrosses may only nest once every two years. They show strong philopatry, meaning they return to their original birth colony to breed. They also return to the exact same nesting site over many years.

These birds can live for many decades. One famous individual named Wisdom is currently around 75 years old.

Flight is another area where these birds show amazing adaptations. Albatrosses and giant petrels use dynamic soaring and slope soaring to save energy. Albatrosses have a special sheet of tendon that locks their wings when fully extended. This allows them to keep their wings up without using any muscle effort.

Smaller birds like the white-faced storm petrel use a different method called pattering. They move across the water surface by holding their feet against the water. They can remain stationary by hovering or using the wind to anchor themselves.