Least Tern

sternula antillarum

least tern

Least tern, photographed at Green Cay Nature Center, Boynton Beach, Palm Beach County, in May 2011.

The least tern, Sternula antillarum, is one of the avian world's ultimate dive bombers. The bird will fly about, hover for second, and suddenly drop straight into the water, emerging with a fish in its mouth.

It's one of the smallest members of the tern family globally, and the smallest found in North America. Like others of its kind, the least tern is a beach bird, but it will venture inland. Far inland. To places like the Dakotas and Colorado.

It's a summer visitor to South Florida and other places in the United States, where they come to breed. Their winter homes are along South America's northern and eastern shores. We tend to see them most frequently in late spring to early summer in places like Green Cay Nature Center or Pine Glades Natural Area, where they fly about looking for aquatic delights. Least terns nest on sandy or pebbly shores, along the coast or inland along a lake or a river. They've been known occasionally to nest in the gravel of a flat-top roof.

In summer, they're commonly found along the Gulf and Atlantic coasts, from Texas to Massachusetts. They're also found along the Pacific Coast from San Francisco Bay south into Mexico. Least terns will also travel inland to nest, particularly along the Mississippi and Missouri rivers and their tributaries. Meriwether Lewis and William Clark first recorded the presence of the least tern at what is now known as Omaha, Neb., in 1804. The inland least tern is federally listed as endangered, mainly because of dwindling habitat for nesting.

Least terns max out at about nine inches long, with a wingspan of about 21 inches. They have a black cap on top of their heads, white face and an orange bill with a black tip. Their bodies are gray-white with black wing tips.

Least terns are colony nesters and fairly adaptable as to where they choose to situate their nests as long as there's water for foraging nearby. Natural nesting sites include isolated barrier-island beaches, but they'll take to spoil islands — piles of dredged sand — gravel roof tops along the coast or inland and even phosphate mines and limestone quarries, according to the Florida Fish and Wildlife Conservation Commission. They'll return to the same site year after year, if they've had success there. If not, they'll try their luck elsewhere.

Least tern males begin courting a prospective mate by offering her dinner and a movie sans the movie. He'll offer her a fish, a shrimp or some other aquatic delight, and if she likes him, the two will begin to scrape out a nest in the sand, lining it with pebbles or grass. They'll produce one or sometimes two broods a year, each with one to three eggs. Both parents incubate the eggs, which take three to four weeks to hatch. The young terns are able to leave the nest after a few days. They'll fledge in about three weeks but usually will stay with their parents for two or three months beyond that. Nesting season in Florida is mid-April to as late as August, though the season might be extended into September by a pair having a second brood.

The least tern population has declined considerably over the last 50 years, and the Union for the Conservation of Nature rates the bird a species of high concern. Coastal development and loss of habitat is the major threat. The North American Waterbird Conservation Plan also lists it as a species of high concern. Florida lists the bird as threatened.

Least terns are members of Laridae, the gull and tern family.

Atlantic Dunes Park

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Published by Wild South Florida, PO Box 7241, Delray Beach, FL 33482.

Photographs by David Sedore. Photographs are property of the publishers and may not be used without permission.