dark tern (14-15 inches, 35-38 cm, total length). The combination of
dark back and white underparts distinguishes the Bridled from all other
terns in the region except the Sooty Tern. Sooty Terns are slightly
larger (17-18 inches) and stockier. Distinctive field marks for the
Bridled Tern include: (1) a white collar that very nearly separates the
dark back from dark head, (2) a contrast between the very dark head and
less dark back and top of the wings, (3) the Bridled Tern's
forehead extends behind the eye, and (4) underwings with more extensive
white than the Sooty Tern's. At sea, they fly lower than Sooty Terns
are seldom seen in flocks.
markings are less defined, backs paler and mottled. Juvenile Sooty
Terns have dark bellies and no white on the face or neck.
'Yerk,' or repeated 'ah-ah-ah . . .' in comparison to the 'wide-a-wake'
or 'wacky-wack' of the Sooty Tern.
a breeding species distributed throughout the Bahamas, Central American
Coast, sporadically in
the Greater Antilies, and throughout most of the Lesser Antilles.
Non-breeding birds occur in Caribbean, Gulf of Mexico and regularly in
Gulf Stream north to the Carolinas. Occasionally further north along
the North American coast. Commonly displaced by storms.
Alternate Common Names
French: Sterne à
collier, Sterne bridée, Oiseau fou, Touaou, Dongue
embridado, Charran monja, Charran sombrio collarino, Golandrina-marina embridada, Gaviotin
embridado, Bubi, Gaviota, Gaviota oscura,
Gaviota monja (Spanish).
of four species of dark-backed pelagic terns (Gray-backed Tern, Sooty
Tern, and Aleutian Tern). Though generally compared to the Sooty Tern,
Bridled Terns are more structurally similar to Gray-backed Terns in
skeletal and external characteristics. They exhibit conspicuous
differences from Sooty
Terns in the
downy and the first basic plumages.
Sterna a. melanoptera
breeds in the Bahamas, the Greater and Lesser Antilles, along the
northern coast of South America, on the Caribbean coast of
Central America, off of Africa near Mauritania, and in the
Guinea. Based on slight variations in coloration and tail patterns,
to six races have been recognized. Some authors have suggested that the
sub-specific name recognita
proposed by Mathews in 1912, be for Caribbean birds and that melanoptera be
reserved for populations in the eastern Atlantic. A thorough taxonomic
revision is needed.
subtropical and tropical Atlantic, Indian, and western Pacific Oceans
and in a number of adjacent seas. They are displaced by the Gray-backed
Tern in the Eastern Pacific. In the West Indies region this tern
breeds from Florida Keys and throughout the Bahamas, southward into and
the Greater and Lesser Antilles. Also on scattered offshore
and cays along the Central and South American coasts. Occurs at sea
around nesting sites and post breeding birds move into the Gulf of
Mexico and Caribbean. In the summer Bridled Terns occur regularly as
far north as the Carolinas, following the Gulf Stream. The current
population is thought to be around 8900 pairs.
not been well studied in the Western Atlantic, and there is little
information for Bridled Terns at sea. Migrates away from nesting areas
and typically remains far at sea over deep waters during the
season. Off the Southeastern United States they forage along the outer
continental shelf and in the Gulf Stream. Sea surface temperatures vary
considerably across the shelf edge but their foraging activity seems
confined to zones where average sea surface temperatures are 26-27 C.
They are typically high flying and solitary though they sometimes
gather in small groups over food rich areas. Most foraging occurs along
oceanic fronts. This species and Audubon's Shearwaters are Sargassum
specialists and obtain a large proportion of their prey from the
pelagic alga mats that accumulate along current edges. During foraging
bouts they dip from heights of 3-10 meters. Occasionally, they make
brief plunge-dives but rarely submerge entirely. Bridled Terns feed
primarily on small fishes (10-22 mm) and crustaceans.
contrasting back and white coloration and high flying foraging makes
them visible above the horizon.
often small sand cays subject to frequent erosion. In West Indies,
nesting habitat mostly restricted to small, vegetated offshore cays and
rocks as a result of introduced predators and human activity
on larger islands. Breeding birds forage 2-30 km from breeding
sites. Nest under large rocks, in limestone solution holes, or deep
within overhanging ledges on rock faces, often on the periphery of the
islands. Nest is a depression in sand, or pebble substrate. Lay a
single egg. Incubation 26-33 days, fledging normally 55-62 days. Unlike
Sooty Terns, fledglings do not form creches. Parents continue to feed
young after fledgling and adults have been observed feeding young after
northward dispersal in Gulf Stream off the Carolinas.
estimates include counts of terns from multiple years. Because they
move nesting sites each year, these esimates represent the number of
nesting places in the West Indies, but the true breeding population is
probably less than half of these numbers. This oversampling is an
unresolved problem for the atlas. The current best estimate of the
population is 8900 pairs.
States Virgin Islands
Kitts and Nevis
Vincent and the Grenadines
and declining, but not specifically protected.
Terns often nest at the same sites as Sooty Terns and other
seabirds. These large composite colonies, often consisting of other
species of 'egg birds' need to be patrolled during the early breeding
season. Educational signage for visitors to islands containing nesting
colonies would be useful and could contain contact information for
reporting violations. For sites where ecotourism is a factor walkways
could direct visitors along paths that would keep them away from key
areas. While a large percentage of the regions' population
occurs at a few large colony sites, groups on small isolated
are important too and should be monitored on a regular basis.
other ground nesting seabirds, visits to colonies should be at times
(during the day and season) that have the least impact on the birds.
expanding Laughing Gull populations in the region are of concern, as
these gulls regularly take chicks from unattended nests. Gull control
should be considered for sites where populations are obviously
declining. In some cases, conservation issues may still linger from
earlier human activities; human exploitation of adults, eggs and chicks
has been prolonged since perhaps 5,000 yr BP, with a sudden increase
after European contact. Guano mining between 1850 and 1890 devastated
many seabird colonies.
other West Indian seabirds, Bridled Tern populations are probably
regulated by the amount of available predator-free nesting habitat in
the vicinity of dependable foraging areas. Efforts to expand the number
of nesting sites for this species would be welcome. Exotic mammalian
predator control is a key issue. In the Bahamas and Caribbean, small,
uninhabited islands are traditionally used for
keeping goats and pigs. These animals overbrowse the native vegetation
and prevent successful nesting by Bridled Terns, other seabirds, and
other native island fauna.
predators or other animals that disturb the natural vegetation (rats,
monkeys, mongoose, raccoons, cats, dogs, pigs, sheep, goats, and
cattle) negatively affect this species. Rats and house cats are the
biggest problems at known nesting sites. On one small island
Bahamas, Bridled Terns nested only on the half of the island with
native vegetation and shunned the half of the island that was dominated
by Australian Pines.
other concerns expressed for the regions' seabird fauna can
also apply to this species and conservation decisions need to be made
a site-to-site basis. In all cases, these birds are now restricted to
undeveloped islands and cays.
sea, this tern is not recorded as a by-catch species. They do, however,
floating plastics that remain in their digestive tracts and can cause
choking. Birds affected by oil spills (as a result of the
Gulf War in Middle East) are documented to abandon nests and have
lowered breeding success in the year following the spill. The fact that
the birds do not settle directly on the water somewhat reduces risk of
oiling, but, apparently, they are still affected by surface oil when
foraging. Bridled Terns have higher concentrations of heavy metals than
other Western North Atlantic terns.
J. W., and R. D. Morris. 1987. Trapping and color banding Brown Noddy
Tern adults at the breeding colony. Colonial Waterbirds 10: 100-102.
J. W., R. D. Morris, J. F. Parnell, and J. Pierce. 2000. Status and
for Laughing Gulls, Gull-billed Terns, Royal Terns and Bridled Terns in
the West Indies. Pages 65-79 in Status
and Conservation of West Indian Seabirds. Society Caribbean
Ornithology (E. A. Schreiber and D. S. Lee, eds), Special Publication Number 1. 225 pp.
J. C., D. S. Lee, and R. D. Morris. Bridled Tern (Sterna anaethetus).
In The Birds of North
America. No. 468 (A. Poole and F. Gill, eds.). The Birds of North
America, Inc., Philadelphia, PA.
by: Dave Lee and Will Mackin,
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.
February 18, 2009