INTERIOR LEAST TERN

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U.S. Fish & Wildlife Service

Sterna antillarum anthalassos

Federal Status: Endangered (May 28, 1985)
State Status: Endangered (December 20, 1989)

Description: Smallest tern in North America. Breeding-plumaged adults light gray above, white below. The two outermost primaries and associated coverts are black, creating a distinctive narrow black wedge on the leading edge of the outer wing that is visible when flying. Forehead white but crown and nape black. Black line runs from nape, through eye, to base of bill. Tail short; deeply forked. Bill yellowish with black tip; slender. Legs and feet yellow. Winter adults have white streaking in black crown and nape; bill dark. Juveniles light brown above with distinct pale edges to the feathers, which results in scaly appearance; dark band along entire leading edge of wing visible both when flying and landed; bill and legs dark. Adults to 24 cm (9.5 in) total length; wingspread to 50 cm (14.7 in). No other adult tern possess a slender yellow bill, white forehead and narrow black band on leading edge of outerwing. Juvenile and winter plumages also distinctive. Nests in a variety of open, unvegetated habitats near good feeding areas, especially exposed sand bars. Lays 2 eggs in unlined scrape; incubation period 2 0-22 days. Flight very light, graceful and buoyant; wingbeats rapid. Feeds primarily on small fish; also crustaceans.

Habitat: Breeds on sand or gravel bars of rivers or lakes.

Distribution: Widely distributed but local during the nesting season. Along major rivers (Mississippi, Red, Colorado, Riq Grande, Missouri and Ohio) in interior North America. Winters along the Pacific coast of Mexico, possibly south to northwestern South America, and along the coast of northern South America. In Louisiana, nests on sand bars in upper Mississippi River. No documented winter records from Louisiana. Another subspecies, S .a. antillarum, which is not federally or state protected as threatened or endangered, is common along the Louisiana coast during breeding season.

Reasons for decline: Habitat loss and human-caused changes in river hydrology from damming and channelizing are primarily responsible for the decline in Least Terns. Additional limiting factors may be predation and human disturbances of nesting colonies, oil spills, and severe weather conditions.

March 2004

Conservation efforts:

1. Identify and protect nesting colonies.
2. Increase public awareness of species and its habitat requirements through educational materials.
3. Study nesting chronology and production in relation to river stages
4. Study interactions between coastal and interior nesting colonies.
5. Compare reproductive success of coastal vs. urban vs. riverine colonies.