Terns are a group of slender, graceful seabirds found across the globe, typically inhabiting areas near oceans, rivers, or wetlands. These birds are known for their elegant flight and their remarkable ability to fish. Terns are part of the Laridae family, which also includes gulls.
Key Physical Features
Terns are generally medium-sized birds, with lengths ranging from approximately 9 inches (23 cm) for the Least Tern to about 22 inches (56 cm) for the Caspian Tern. Terns possess long, narrow, and pointed wings, often exhibiting an angular shape and pointed wingtips. This wing design contributes to their agile and buoyant flight, characterized by rowing wingbeats.
A distinctive feature of many tern species is their forked tail, which can be deeply V-shaped in sea terns. This forked tail, along with their long, narrow wings, lends an elegant appearance during flight. Their bills are typically sharp and pointed, varying in color among species, often appearing black, red, or yellow.
Plumage patterns in adult terns are usually light gray or white on the body, contrasted by a black cap on the head. While male and female terns generally have identical appearances, young birds can be distinguished from adults, often displaying a more subdued or mottled plumage. In non-breeding seasons, the black cap may be reduced, and the forehead might turn white.
Where Terns Live and How They Behave
Terns inhabit a wide array of aquatic environments across the world, from coastal areas to inland lakes and rivers. They are commonly found along beaches, estuaries, and barrier islands, but some species also nest in freshwater marshes. Many tern species are long-distance migrants, with the Arctic Tern undertaking the longest annual migration of any bird, traveling between its Arctic breeding grounds and Antarctic waters.
Their diet primarily consists of small fish, which they capture through a characteristic hunting method involving diving. Terns often hover over the water before plunging headfirst to seize their prey just below the surface. They can also snatch items directly from the water’s surface or even pursue flying insects. Some terns, like the Marsh Terns, specialize in catching insects in the air or from freshwater surfaces.
Terns exhibit highly social behaviors, frequently forming large colonies for breeding. These colonies can range from dozens to millions of individuals, depending on the species. Within these colonies, terns engage in courtship displays and vocalizations. They typically construct simple nests, which may be a bare scrape in sand or gravel, sometimes lined with debris, on beaches or islands. Both parents usually participate in incubating the eggs and feeding the young.
Distinguishing Terns from Gulls
Terns are often confused with gulls due to their shared family, Laridae, but several distinct features differentiate them. Terns possess a more slender build and lighter body compared to the larger, heavier gulls. Their wings are longer, narrower, and more pointed, which gives them a more agile and elegant appearance in flight. Gulls, conversely, have broader wings and a heavier, more direct flight pattern.
A key distinction lies in their bill shape; terns have sharp, pointed bills suited for plunge-diving for fish. Gulls, however, typically have stouter, often hooked bills. The tail shape also differs significantly; most terns have deeply forked tails, sometimes earning them the nickname “sea swallows,” while gulls tend to have rounded or squared tails.
Behaviorally, terns are renowned for their method of hunting by diving into the water for fish. They frequently hover before diving, often with their heads pointed downwards, scanning the water. Gulls, on the other hand, are more generalist feeders. While terns rarely swim despite having webbed feet, usually landing on water only to bathe, gulls are more commonly observed floating on water.