The Least Tern (Sterna antillarum) is our smallest tern species. By early May this little one-ounce dynamo has returned to Connecticut from a winter in Central and South America. (Records show that Least Terns banded in our state have been found spending the winter along the coast of Guyana in South America.) Given the chance, this state-threatened species will breed and raise its young along several of our sandy beaches this spring and summer.
An adult is about nine inches long, with a 20-inch wingspan. It is a crisp, clean white, with a pale gray back. The edges of its long, pointed wings are dipped in black and during the breeding season its bill and legs are bright yellow. Like other terns in our area, it has a black cap on its head, but the least tern has a white forehead patch that makes it distinctive.
It feeds on small fish and crustaceans by hovering and diving into the water, or by skimming the water’s surface. Silver¬sides, sandlances, sand eels and shrimp are preferred foods.
The Least Tern nests in colonies along the coast in the East, from Mexico to Maine. Subspecies can be found breed¬ing along the Mississippi River and the Pacific coast. It requires open sandy beaches with no vegetation and prefers areas close to the mouth of a channel. As shoreline development for housing and recreation claims the beaches, Least Tern nesting sites continue to disappear. The quality of sites that remain becomes increasingly important to the survival of this threatened species. In Connecticut, Least Tern populations have declined by 75% in the past 20 years.
A simple scraped depression among sand and shells becomes its nest. One to three buff eggs spattered with dark splotches are laid in the depression, blending perfectly with their surroundings. They hatch in 21 days and the downy young leave the nest a day later. They are able to fly in three weeks, but will continue to be fed by their parents while they master their hunting and diving skills.
The protective adults defend their nest of eggs or their hatched young by dive-bombing any intruders. Unfortunately, frequent disturbances will prevent the adults from incubating the eggs or feeding their young. Too often, Least Tern breeding fails due to human-caused disturbances, such as oblivious sunbathers, roaming dogs and cats, and raccoons and skunks attracted to discarded beach trash. Beach areas supporting Least Tern nests are fenced off and posted with signs by the Connecticut Department of Environmental Protection to alert the public to the presence of the nests.
Observe nesting terns from a distance using binoculars and you may see an adult hover above the surf on rapid wingbeats before it dives for a meal. You may see it return to feed its downy young with a tiny fish in its bill. Get too close and all you will observe is a pair of upset parent birds as they frantically try to protect their young from an inconsiderate intruder.
[Audubon’s Climate Report lists the Least Tern as Climate Endangered.]