Status: Endangered (50 FR 21784; May 28, 1985). Critical habitat has not been designated.
Description: The interior least tern is the smallest member of the tern family with a wingspan of 20 inches (50 cm).
They have a grayish back and wings, and snowy white undersides. Least terns can be distinguished from all other
terns by their combination of a black crown, white forehead, and a variable black-tipped yellow bill.
Life History: Interior least terns arrive at breeding sites from late April to early June where they typically spend
four to five months. Pairs go through an elaborate courtship period that includes courtship feedings and a variety
of postures and vocalizations. Least terns nest in small colonies on exposed salt flats, river sandbars, or reservoir
beaches. Nests are small scrapes in the sand, and usually two or three eggs are laid. The young are fairly mobile
soon after hatching. Both parents feed the young and remain with them until fall migration. Terns will travel four
or more miles (6+ km) from their breeding colonies to find the small fish that make up the major part of their diet.
Habitat: Interior least terns favor islands or sandbars along large rivers for nesting. The sand must be
mostly clear of vegetation to be used by terns. Least terns prefer shallow water for fishing. Water levels must be
low enough so that nests stay dry.
Distribution: The historic distribution of the interior least tern was the major river systems of the midwestern
United States. These rivers included the Red, Rio Grande, Arkansas, Missouri, Ohio, and Mississippi river systems.
Currently, they occur as small remnant colonies throughout their former range. In Oklahoma, interior least terns
nest along most of the larger rivers, as well as at the Salt Plains National Wildlife Refuge near Jet, Oklahoma. Interior
least terns winter in South America.
Causes of Decline: Many nesting areas have been permanently flooded by reservoirs and channelization
projects. Unpredictable water discharge patterns below dams flood nesting areas. Overgrowth of brush and trees
also eliminates remaining habitat. This prevents terns from using these areas as nesting sites. The recreational
use of sandbars by humans is a major threat to the tern's reproductive success.
Recovery Needs: Primary recovery tasks for interior least tern populations include determining
population trends and habitat requirements, increasing breeding populations, and developing public awareness
of the needs of least terns through educational programs.
Other information: The recovery plan for the interior least tern was released in 1990. The United States
Fish and Wildlife Service is working with various state and federal agencies to monitor and protect the least tern.
In Oklahoma, they are working with the Nature Conservancy to protect tern habitat along the Arkansas River near
Tulsa, and along the Canadian River near Norman.
