Least tern: Sternula antillarum
Genus/Species: Sternula antillarum
Common Name: Least tern
Federal Status: Endangered in Midwest and Great Plains states
FL Status: State-designated Threatened
FNAI Ranks: G4/S3 (Globally: Apparently Secure/State: Rare)
IUCN Status: LC (Least Concern)
The least tern is the smallest tern in North America. Least terns can reach a length between 8.3-9.1 inches (21-23 centimeters) with a wingspan of 21-23 inches (53-58 centimeters) (Thompson et al., 1997). Least terns have long pointed wings and a deeply forked tail. Other physical characteristics include a yellow beak, gray back, white belly, and black cap.
The least tern’s diet primarily consists of fish, but they will also feed on small invertebrates. (The Cornell Lab of Ornithology, 2011).
Male least terns have a unique courtship ritual. During courting, the male will offer the female food in hopes of gaining her choice as a mate. Once the two mates are together they will begin building the nest in shallow depressions in bare beach sand. Least terns will also build nests on gravel rooftops. Least terns lay eggs between the middle of April and the beginning of May. The eggs are camouflaged to help prevent predation. Egg incubation lasts for 21 days. Young least terns are able to leave the nest three to four days after hatching.
Habitat and Distribution
The least tern inhabits areas along the coasts of Florida including estuaries and bays, as well as areas around rivers in the Great Plains (Florida Natural Areas Inventory 2001). In Florida, the least tern can be found throughout most coastal areas. Outside of Florida, least terns are found along the U.S. Atlantic Coast, mid Atlantic states, and down from Mexico to northern Argentina (Florida Natural Areas Inventory 2001).
The least tern faces many threats as the human population increases along the coasts. The main threat to the least tern population is habitat loss. Loss of habitat is often attributed to coastal development. Coastal development causes damage to least tern habitat because of the building on the coasts, human traffic on the beaches, and recreational activities. Increased numbers of predators due to the larger amounts of available food and trash for scavenging are also a threat to the least tern. Predators can cause destruction to breeding colonies while they are nesting by destroying nests and eating chicks and eggs. Also, global climate change is an impending threat to the least tern. Rising sea levels and more frequent strong storms may damage and destroy least tern nests, as well as habitat. Spring tides can also cause flooding of least tern nests. Other threats to the least tern include shoreline hardening, mechanical raking, oil spills, response to oil spill events, and increased presence of domestic animals (Defeo et al. 2009).
Conservation and Management
The least tern is protected by the U.S. Migratory Bird Treaty Act. It is also protected as an Endangered Species (Midwest and Great Plains states only) by the Federal Endangered Species Act and as a State-designated Threatened species by Florida’s Endangered and Threatened Species Rule .
Biological Status Review (BSR)
Supplemental Information for the BSR
Species Action Plan
Other Informative Links
Encyclopedia of Life
FWC Species Profile
FWC - Florida's Breeding Bird Atlas
Florida Natural Areas Inventory
International Union of Conservation of Nature
The Cornell Lab of Ornithology
Printable version of this page
BirdLife International. 2009. Sterna antillarum. In: IUCN 2010. IUCN Red List of Threatened Species. Version 2010.4. Available online at http://www.iucnredlist.org/details/22694673/0 . Last accessed 03/11/2011.
Defeo, O., A. McLachlan, D.S. Schoeman, T.A. Schlacher, J. Dugan, A. Jones, M. Lastra, and F. Scapini. 2009. Threats to sandy bhulzeach ecosystems: A review. Estuarine, Coastal and Shelf Sciences 81: 1 – 12.
Florida Natural Areas Inventory. 2001. Field guide to the rare animals of Florida. http://www.fnai.org/FieldGuide/pdf/Sterna_antillarum.pdf . Accessed on 11 March 2011
The Cornell Lab of Ornithology. (2011). Least Tern. Retrieved March 11, 2011, from All About Birds: http://www.allaboutbirds.org/guide/Least_Tern/lifehistory .
Thompson, Bruce C., Jerome A. Jackson, Joannna Burger, Laura A. Hill, Eileen M. Kirsch and Jonathan L. Atwood. 1997. Least Tern (Sternula antillarum), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online.
Image Credit Photo courtesy of Alex Kropp, FWC