Least Tern

Sterna antillarum

The Least Tern is the smallest of the North American terns.  They breed in two distinct habitats, the sandy beaches of the Atlantic and the Californian Pacific coast, and on sandbars on large river systems in the interior of the country.  Both the coastal and inland populations are endangered.  In South Dakota, they breed along sandbars of the Missouri River system, but are endangered by the unnatural fluctuations in river levels caused by management of water releases from Missouri River system dams.  Along the coastlines, they are endangered by human disturbance on their nesting beaches.  There is some hope that coastal populations, at least, have adapted to a human presence somewhat by including gravel roofs as areas to nest.

Habitat: In the interior of the country, breeds on large river systems with large exposed sandbars.  Along the coastline, breeds on sandy beaches adjacent to shallow water.  During the winter, found along tropical coastlines and sometimes far out to sea.

Diet: Primarily feeds on small fish, crustaceans, and insects.  Will also eat small mollusks and marine worms if available.

Behavior: Forages while in flight, hovering over the water and plunging down just below the surface to capture fish and other prey items when spotted.  They are also capable of catching flying insects while in flight.

Nesting: May through July

Breeding Map: Breeding Bird Survey map

Song: Loud piercing kip-kip-kip, and grating zr-e-e-e-ep.   Click to listen to Least Tern song.

Migration: In summer, can be found locally inland on large river systems, along the Atlantic coast, and locally along California's Pacific coast.  Both coastal and interior populations migrate well to the south in winter, inhabiting tropical waters down through Brazil.

Similar Species: Black Tern (in non-breeding plumage)

Conservation Status: Endangered in many parts of its range.  In the interior of the continent, unnatural water fluctuations due to regulation of rivers with dams often results in unsuccessful nesting.  On the coastlines, human disturbance on beach nest sites often causes unsuccessful nesting.

Further Information: 1) Patuxent Bird Identification InfoCenter, Least Tern

2) Cornell University's "All About Birds - Least Tern"

3) eNnature.com -- Least Tern

Photo Information: Photo taken near Pierre by Doug Backlund