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Least Tern Sterna antillarum antillarum


Least Tern

At a glance

Smallest of the region’s terns

A coastal species, requiring open sand flats and beach dunes for nesting

Rarely seen out of sight of land even during migration

Recreational beach use and development is major conservation issue

Index

Identification

Small tern (8-11 inches; 20-28 cm, total length) in hand. When seen with other terns, size alone will sepertate this species from other North Atlantic terns. Hovering flight and size will distinguish this species from all other terns in region.

Adults

Known to live for 24 years. Breeding season adults have a black cap and a narrow yellow, black tipped bill. Legs and feet yellow. In the non-breeding season, the bill is black and the cap is less distinct and mottled with white. Sexes alike, males slightly larger than females.

Juveniles

The younger birds have dark bills and are light grey dorsally. Crown of cap not well defined.

Alternative names

French: Petite Sterne

Spanish: Charran minimo, Golondrinita marina, Gallito

Scientific: Eurasian Little Tern or Sterna albifrons in some books

Systematics

Least Tern of North America and Little Tern of Eurasia considered sister species. Other closely related taxa in Indian, and South Pacific Oceans, and Australia. Five subspecies of S. antillarum described, but little basis for separation and distinctions dubious. S. a. antillarium is only subspecies breeding in region. Interior Least Tern, S. a. aathalassos, from inland North America probably migrates through West Indies region.

Likely locations

Coastal areas, relatively open beaches.

Distribution

This tern, along with its closely related members of the same super species (Little Tern, Fairy Tern and others), is cosmopolitan in distribution but absent from the South Atlantic. A number of inland populations occur along rivers in North America and in Europe. Absent from Bermuda.

In the western North Atlantic it occurs as a breeding species along the Atlantic and Gulf of Mexico coasts, West Indies, and southern Caribbean coast of Central and northern South America.  Wintering birds are found along the South American coast south to northern Brazil.

Within West Indies breeds throughout Bahamas and on all island groups.

Biology

At sea

Feeds primarily on small marine and estuarine fish, but also shrimp and occasionally other invertebrates. Does not normally flock, but numbers of individuals may focus foraging over patchy prey resources. Diurnal. Searches for prey on the wing while flying or hovering from 1-10 meters above the surface. Plunges to surface but does not submerge. Coastal, feeds in littoral zone, seldom out of sight of land, few pelagic observations.

At the nest

Nest on relatively open beaches and cays kept free of vegetation by storms. Breeds in colonies adjacent to the coast, species has high degree of site fidelity. Sometimes adapts to nesting on gravel rooftops and other predator free developed sites.  Nesting begins between mid April and mid May. Fairly synchronous nesting within colony. Nest simple scrape, bits of shell and other objects occasionally added. Clutch normally 2-3 beige, brown splotched eggs. Average incubation 21-23 days. Young vacate nest at age of about 2 days, first flight at about 20 days.  Young disperse from colony within 3 weeks of fledging, but parents may continue to feed young for up to 8 weeks.

Current Population 

Collectively the terns of this super species’ populations are of considerable magnitude, however these birds do not wander between hemispheres so the information presented here is just for the North Atlantic. This information is for the nominate subspecies Sterna antillarum antillarum.

Country Breeding Sites Low Estimate High Estimate
Bermuda 1 0 0
Bahamas 42 787 1135
Turks and Caicos 8 806 815
Cuba 22 366 420
Cayman Islands 15 397 434
Jamaica 9 28 78
Dominican Republic 3 302 320
Puerto Rico 7 47 145
US Virgin Islands 8 409 757
Anguilla 8 291 343
St. Martin 1 60 65
St. Maarten 1 5 10
St. Bartholomew 1 15 20
St. Christopher and Nevis 4 12 30
Antigua and Barbuda 2 2 20
Guadeloupe 4 50 70
Venezuela 10 228 315
Bonaire 6 70 440
Curacao 6 161 530
Aruba 1 55 55
Total 159 4091 6002


North and middle United States: 7,623 pairs (Buckley and Buckley 1984); SE United States: 13,500 pairs (Clapp and Buckley 1984); Bahamas and West Indies: 1500-3000 pairs (Jackson 2000); Central America: ca 100 pairs (van Halewyn and Norton 1984); islands off Venezuela: ca 1,000 pairs (van Halewyn and Norton 1984).

Total population probably exceeds the figures presented here (32,000+ pairs) in that protection of nesting colonies in the United States has greatly increased the number of viable breeding colonies in the last several decades. However, Kushlan, et al. (2002) report at total of 47,000-51,500 breeding adults for the Americas. This figure is for individuals, not pairs (thus 23-25.75 thousand pairs) and includes inland and west coast races and populations so assessments from the 1980s may still best yet reflect the actual overall western Atlantic population.

Conservation Status

In our area this is not a species of conservation concern. Several of the inland US populations are endangered. In West Indies, many local populations are in decline because of beachfront development and recreational use of beaches. Species documented to have been extirpated from several former nesting islands.

Conservation Needs

Its preferred beach-nesting habitat is also prized for development and recreation. Habitat destruction for beach front resorts and housing and erosion control measures directly destroy nesting habitat. Human presence associated with development (along with pet associates) causes constant disturbance of nesting birds in adjacent areas. Protection of colonies, instructive signs, and seasonal fencing of colony sites would do much to protect these terns. Educational information seasonally provided to tourist staying in beach front resorts in the proximity of tern nesting colonies would limit unintentional disturbance.

Rats and other introduced predators also present problems. Laughing gull breeding colonies in the vicinity of Least Tern colonies would be a negative factor. Egging continues to be an issue in much of the region.

Both the behavior of the bird and its coastal affiliations would make it highly unlikely that this species would be encountered by pelagic fisheries operations, or to be of concern for other marine factors negatively affecting many seabirds.

Management in predator control and removal of dune vegetation at small and former colony sites should be beneficial. Tern decoys have been used in the US to attract nesting pairs and to facilitate recolonization of former sites.

Detailed studies of these terns in the West Indies are lacking.

Photos

     

Selected References:

Buckley, P. A. and F. G. Buckley. 1984. Seabirds of the North and Middle Atlantic coast of the United States: their status and conservation. Pp 101-133. in J. P. Croxall, P. G. Evans and R. W. Schreiber (eds.). Status and Conservation of the World's Seabirds. ICBP Tech. Publ., No. 2. 778 p.

Clapp, R. B. and P. A.Buckley. 1984. Status and conservation of seabirds in the southeastern United States, Pp. 135-155. in J. P. Croxall, P. G. Evans and R. W. Schreiber (eds). Status and Conservation of the World's Seabirds. ICBP Tech. Publ., No. 2. 778 p.

Jackson, J. A. 2000. Distribution, population changes and threats to Least Terns in the Caribbean and adjacent waters of the Atlantic and Gulf of Mexico. Pp. 109-117. in E. A. Schreiber and D. S. Lee (eds.) Status and Conservation of West Indian Seabirds. Society of Caribbean Ornithology, Special Publication Number 1.225 pp.

Kushlan, J. A. 2002. Waterbird Conservation for the Americas: the North American Waterbird Conservation Plan, Version 1. Waterbird Conservation for the Americas, Washington, DC, USA., 78 pp.

Thompson, B. C., J. A. Jackson, J. Burger, L. A. Hill, E. M. Kirsch, and J. L. Atwood.  1997. Least Tern (Sterna antillarum). In The Birds of North America, No. 290 (A. Poole and F. Gill, eds.). The Academy of Natural Sciences, Philadelphia, PA, and The American Ornithologists’ Union, Washington, D.C.

Van Halewyn, R. and R. Norton. 1984.The status and conservation of seabirds in the Caribbean. Pp. 169-222. in J. P. Croxall, P. G. Evans and R. W. Schreiber (eds). Status and Conservation of the World's Seabirds. ICBP Tech. Publ., No. 2. 778 p.

West Indian Breeding Seabird Atlas by Will Mackin and David Lee is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 United States License. Based on work at www.wicbirds.net. Permissions beyond the scope of this license may be available at www.wicbirds.net.

Suggested citation: Lee, D. S., W. A. Mackin. 2008. Least Tern. West Indian Breeding Seabird Atlas <http://www.wicbirds.net/lete.html>. Last Updated: _____. Date accessed: ______.

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