Featured Rare Bird of the CT River: Least Tern

Least Tern (Sternulla antillarum) Fun Facts

Length: 8 1/2 – 9 1/2 inches long
Wingspread: about 20 inches
Favorite Food: sand eels and shrimp
Nest: simply a depression or hollow in the ground on the beach above the hightide line, often in association with Piping Plovers
Eggs: usually two, laid between late May and early August; incubated for 20-22 days
Range: Atlantic coast population ranges from Maine to Florida

Least Tern
Least Tern (Photo by Anthony Zemba)

The Least Tern is a sleek little shorebird related to gulls (Family Laridae).  Populations of this species are listed as threatened under the State of Connecticut Endangered Species Act.

Least Terns breed in sparsely vegetated open sand, gravel, or cobble beaches frequently adjacent to sand dunes (Degraaf and Yamasaki, 2001). The Atlantic Coast population breeds on sandy beaches along the east coast of North America, from Maine to Florida. There are about a dozen nesting localities in CT, but not all localities consistently support breeding pairs from year to year.  The Least Tern is a colonial nester and the more pairs that breed at a given location, the greater the chance the colony has at successfully rearing young to fledging.  The Connecticut River estuary is one of the various historically used nesting sites that has supported successful breeding colonies in year’s past.

Least Terns arrive in Connecticut beginning about May 1st (Haniseck, 2005) after spending the winter somewhere from the Gulf of Mexico, south to Peru and Brazil (Terres, 1980).  By the end of May, these gregarious shorebirds lay two eggs in a scrape in the sand just above the high tide line.  Wildlife technicians from the CTDEEP typically erect symbolic string fencing along the high-tide line to remind people walking the beach to remain below the high tide line so as not to step on eggs, or young.  The adults, eggs, and chicks have effective protective coloration, which provides excellent camouflage amongst the sand, shell hash, and wrack line of the beach. The chicks are mobile and able to leave the nest scrape two days after hatching and become capable of flight after about 20 days. Pairs will re-nest if the first nest is washed away by spring tides or lost to predation or disturbance.  (Thompson et al., 1997). By early September adults and hatch year birds are moving south to wintering grounds.

Major threats to the breeding success of this species in CT are similar to those that prey on Piping Plovers (see Blog Post for Piping Plovers).  They include predators such as foxes, raccoons, opossums, skunks, feral and free-roaming cats, free-roaming dogs, predatory and scavenging birds, and humans.  Extreme heat or cold stress may impact nesting success as well. Connecticut beaches tend to be narrow in cross sectional profile and thus both Least Terns and Piping Plovers may be exposed to intense human pressure proximal to their nesting sites on the high beach above the high tide line.  As the weather warms, and the state slowly begins to reopen in the wake of the COVID-19 Pandemic, larger crowds may begin to form on our beaches.  Once again, we remind you that where you see signs informing the public of beach-nesting birds such as the Piping Plover and the Least Tern, please respect the warnings to stay out of roped-offed areas demarcating their nesting territories, and do not bring your dogs to beaches with nesting colonies of these rare species.  Again, if we respect their space, and continue to “share the shore” responsibly, we will be able to avoid the beach closures at sites supporting nesting pairs of this state threatened species.

One can find more information on Connecticut’s rare species at the following link:


Information on the Connecticut Breeding Bird Atlas can be found here: http://www.ctbirdatlas.org/


CTDEP/CTDEEP. 1992, 1993, 1995, 1998, 2004, 2010, 2015. Connecticut’s Endangered, Threatened and Special Concern Species. State of Connecticut Department of Environmental Protection, 2015: http://www.ct.gov/dep/cwp/view.asp?a=2702&q=323488&depNav_GID=1628

Thompson, B.C. , J.A. Jackson, J. Berger, L.A. Hill, E.M. Kirsch , and J.L. Atwood. 1997. Least Tern (Sterna antillarum). In: The Birds of North America #280. A. Poole and F. Gill, eds. The Academy of Natural Sciences. Philadelphia, PA and the American Ornithologists’ Union, Washington, D.C.

DeGraaf, R. M., & Yamasaki, M. (2001). New England Wildlife: Habitat, Natural History, and Distribution. Hanover, New Hampshire: University Press of New England.

Terres, John K. (1980). The Audubon Encyclopedia of North American Birds, Alfred A. Knopf, NY. 1109 pp.

Contributed by Anthony Zemba.

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