James L. Cummins

The Least Tern by James L. Cummins

The least tern is the smallest of the American terns and is typically found nesting on sandy beaches along the Southern coasts of the United States and up the major river systems into the interior of the continent. A species of tern that breeds in North America and into South America, the least tern is closely related to the little tern of the Old World. 

Although widespread and common in places, the least tern is migratory, wintering in Central America and the Caribbean. Approximately 9 inches in length, the least tern, unlike the gull, will dive into water for small fish. The body of these terns is predominately gray and white, with black streaking on the head, but they have distinctive yellow bills and legs. Least terns have a forked tail and narrow, pointed wings. Least terns that are less than a year old have less distinctive black streaking on the head and less of a forked tail. These birds fly with very rapid wingbeats. The least tern arrives at its breeding grounds in late April. 

The breeding colonies are not dense and often appear in areas free from humans or predators, along marine shores or on sandbar islands in large rivers. Only after courtship has confirmed mate selection will the nesting begin–usually around mid-May. Nests are generally situated on barren to sparsely vegetated places close to water. While nesting density is usually low in a given area, the most common clutch size per nest can be as much as four per nest. 

Both female and male incubate the eggs for a period of about 3 weeks and both parents are involved in the care of the young. Young birds can fly at the age of 4 weeks. This means that the nesting population has usually vacated the breeding grounds no later than the end of August. The least tern hunts primarily in shallow estuaries and lagoons, where smaller fishes are abundant. It can be observed hovering until it spots its prey, at which point it plunges into the water without full submersion to extract its meal. 

The favored meal of the least tern includes smelt, silversides, shiner surfperch, and small crustaceans. While adults do not require cover from the elements, the young chicks require wind blocks and shade to protect them. Predators of the least tern include burrowing owls, American kestrels, coyotes, great blue herons, Mississippi kites, and even feral dogs and cats. No other North American tern approaches the least tern in size except the black tern. While the black tern is closest in size, it has a swallow-like flight, rarely dives for prey, is dark gray above, has a dark gray tail, and is entirely dark below in adult alternate plumage. In comparison to the flight of its closest relatives, the wingbeats of the least tern are often so rapid that they cannot be counted.

James L. Cummins is executive director of Wildlife Mississippi.

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