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New Jersey Endangered and Threatened Species Field Guide


Image of An adult Least tern.Zoom+ An adult Least tern. © Chris Davidson

Least tern

Sternula antillarum

Species Group: Bird

Conservation Status

State: Endangered

 


Identification

The least tern is the smallest of the North American terns (about 9 in. in length). It has a black-cap with a white forehead. A black eye-line connects the black cap to the bill. It has white underparts and gray upper body, wings and a forked tail. The least tern can be distinguished by its sulfur yellow bill, which has a black tip. In fall, the black cap retreats, with black covering only the back of the head and a line through each eye. The bill and legs also lose their yellow color, turning dusky to black. Sexes are similar in coloration but females are slightly smaller than males.

Juvenile birds are similar to non-breeding adults, but the upper body may be more brownish gray and there is even less black on the cap.

Least terns produce several calls, more musical and high pitched than other terns, and described variously as kip, kip, kip or kit-kit-kit, and kid-ick, kid-ick, and also a rasping zr-e-e-e-p. Calls are often given in such rapid succession that two or three birds can sound like a large flock.

Image of Range of the Least tern in New Jersey.Zoom+ Range of the Least tern in New Jersey.

Distribution and Habitat

The least tern is largely distributed in North America. Populations can be found along the Pacific Coast of California and Mexico, along many of the interior rivers, and along the Atlantic and Gulf Coasts.

Colonies of least terns in New Jersey of a few to several hundred pairs are found primarily along barrier island beaches or mainland beach strands. Bare sandy areas or areas sparsely vegetated that are above spring (full moon) high tides are preferred. Nesting colonies are also found on sandy dredge disposal sites before the establishment of dense vegetation. Least terns may also nest near sand and gravel pits where sand piles from mining operations provide suitable nesting habitat. The birds typically forage in bays, lagoons, estuaries, rivers and lakes along the coast.

Diet

Least terns eat small fish and occasionally shrimp and other marine invertebrates. They hover above the water then plunge from 3 to 10 ft. down to dive after prey. They grasp the prey with their bill and are usually eaten in flight.

Life Cycle

In late April to early May terns return to coastal nesting areas in New Jersey. They are often heard than seen while calling over and around coastal nesting areas. Courtship and colony establishment begins in the first week of May. Male terns call (with fish in their bill) while being pursued by other males or females. Males often perch and offer food to female terns.

They nest in shallow scrapes that are made by both the male and female. They sit in the sand and kick their feet backward while rotating to make a shallow bowl-like depression in the sand. They may make several scrapes, but they only use one. The female selects the scrape and from mid to late June she lays two to three sand-colored eggs. The eggs are highly camouflaged and are speckled with many brown spots.

Image of Least tern in flight.Zoom+ Least tern in flight. © Steve Byland

The eggs are incubated for approximately 21 days by both the male and female. The young hatch with their eyes open and are covered in light downy feathers. They do not leave the scrape for the first couple days of life. Soon after, the young walk about in search of their parents for food. The young are closely brooded by the parents, especially at night, to be kept warm and shielded from the elements. The young fledge in about three weeks. The adults continue to feed the young for up to 8 weeks after they fledge. Juvenile terns often form large groups with other juveniles that are guarded by a few adults. Adults are able to identify their young by their calls.

Current Threats, Status, and Conservation

The least tern was once a common breeder along the New Jersey coast. In the early 1900s egg collecting and hunting for the use of their feathers had decimated least tern populations. Protection by the Migratory Bird Treaty Act of 1918 and changing fashion trends enabled Least Tern numbers to rebound. However, since the late 1940s, coastal development and the elevated recreational use of beaches began another population decline. Populations have stabilized in recent decades as management measures were implemented, but recently, populations have begun declining again, due primarily to predation losses and increases in losses to coastal flooding.


Text derived from the book, Endangered and Threatened Wildlife of New Jersey. 2003. Originally written by Dave Jenkins. Edited by B.E. Beans & L. Niles. Edited and updated in 2010 by Ben Wurst.


Scientific Classification

Kingdom: Animalia
    Phylum: Chordata
       Class: Aves
          Order: Charadriiformes
             Family: Laridae
                Genus: Sternula
                   Species: S. antillarum

Find Related Info: Beach Nesting Birds, Endangered

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