A shearwater is a long-winged seabird belonging to the family Procellariidae, which also includes petrels and fulmars. They are part of the order Procellariiformes, often called “tubenoses” due to a distinct feature on their bill. Shearwaters are highly pelagic, spending almost their entire lives over the open ocean, far from coastlines. They are globally distributed, though most common in the temperate and cold waters of the world. Their existence is characterized by impressive aerial efficiency and some of the longest migratory journeys undertaken by any animal.
Physical Traits and Classification
Shearwaters are characterized by a medium-sized body and long, narrow, stiff wings built for energy-efficient gliding flight. Their plumage is generally subdued, often exhibiting a pattern of dark brown or black on the upper surfaces and lighter white or gray on the undersides. This countershading helps to camouflage them against the water’s surface from both predators above and prey below.
The defining anatomical trait of the Procellariiformes order is the “tubenose” structure on the bill, which consists of tube-like extensions over the nostrils. This unique adaptation is directly linked to the birds’ oceanic diet and ability to drink saltwater. The tubes house the ducts of a specialized salt gland, which efficiently excretes excess sodium and chloride ions ingested with their food and seawater.
The bird’s legs and webbed feet are relatively short, positioned far back on the body, which aids in swimming and diving underwater. This rearward placement makes walking on land awkward, resulting in a shuffling gait. Shearwaters only return to land to breed, typically nesting in burrows or rock crevices on remote islands.
Global Migrators: Habitat and Range
Shearwaters are among the most accomplished long-distance travelers in the avian world. Their habitat is exclusively marine, meaning they are found across all the world’s oceans, from the Atlantic to the Pacific.
Many species undertake spectacular trans-equatorial migrations, moving between breeding colonies in one hemisphere and feeding grounds in the opposite. The sooty shearwater, for instance, is famous for its figure-eight migration route that can cover distances of up to 40,000 miles in a single year, one of the longest migrations of any bird species. After breeding in the Southern Hemisphere near places like New Zealand and the Falkland Islands, they journey to the feeding-rich waters of the North Atlantic and North Pacific.
Their widespread distribution reflects their ability to exploit seasonal food availability across vast oceanic distances. Most of their life is spent airborne or resting on the water, following prevailing winds and currents to locate concentrations of small fish, squid, and crustaceans.
The Signature Behavior: Why They Shear the Water
The name “shearwater” comes directly from the bird’s unique and highly efficient flight technique over the ocean surface. They utilize a method of flight known as dynamic soaring, which allows them to harvest energy from the wind gradient above the waves. This involves a repeated cycle of gliding down into the trough of a wave, gaining speed, and then climbing up the windward side of the next wave to gain altitude and energy.
This dynamic soaring is executed with stiff, outstretched wings and involves flying extremely close to the water. The bird often flies so low that its wingtips appear to slice or “shear” the surface of the waves, which is the visual cue that gave the bird its common name. This flight style allows them to travel great distances with minimal effort.
Shearwaters use this low-altitude, energy-saving flight to locate and access their prey. Their feeding behavior typically involves surface plunging or dipping to catch small prey items like fish and squid near the water’s surface. Some species are also capable of diving to considerable depths, using their wings for propulsion underwater to pursue food.