Another
medium sized (35-43 cm (14-17 inches) total length) white tern with a
black cap. Bill is all black and shorter and thicker and its body more
robust than other similar appearing terns. Legs black. Non-breeding
birds lack cap but have black extending from eye toward back of head. Birds feed with
characteristic swooping pattern over marsh habitat that is unique among
terns in this region.
Adults
First
breed at 5 years of age. Life span may be as much as 16 years. Black
cap absent on non-breeding birds, top of head white. Post breeding
adults and juveniles both have dark eye patch.
Juveniles
Rear
of crown and nape have brownish cast. Back tan with brown spots on
wings.
Alternative names
French:
Sterne Hansel
Spanish:
Pico de gaviota, Golondrina playera, Gaviota piquigorda.
Systematics
Some
authors consider this species to represent a monotypic genus-- Gelochelidon.
Cosmopolitan tern divided into as many as six subspecies recognized by
variations in plumage and size. Two New World subspecies, the eastern
North American one (S.
n. aranea)
breeds from Long Island (NY) south along coast to Gulf Coast, also
Bahamas and northern Antilles. Pacific coast subspecies is larger.
Likely locations
Open
sand flats, secondary sparsely vegetated inter dunes, and marshes in
northern West Indies region. Regular on most major Bahaman islands but
breeding not often confirmed.
Distribution
Found
in both the New and Old World. In West Indies region breeds only in
Bahamas and northern Antilles, absent from Bermuda. This is not a
species that is normally found in pelagic habitats. Unlike other terns,
Gull-billed Terns feed over marshes and open sand flats. A large
percentage (ca. 50%) of the total western Atlantic breeding population
nests on Texas’ Gulf Coast. Winters in south Florida, rarely north to
North Carolina, and along Gulf and Central American Coast. Wintering
status in West Indies unclear.
Biology
At
sea
Not
a primary marine species, feeds over flats, salt marshes and freshwater
and brackish lagoons. Food items typically insects, small crabs,
lizards, and small sea bird chicks. Opportunistic; taking advantage of
locally abundant prey items. Feeds on the wing, hawking insects from
the air and plucks prey from ground after steep swoop. Migrates at sea
but usually over inshore waters.
At
the nest
Monogamous,
often arriving in pairs at nesting sites. Nest on open flats, inter
dunes, open sandy washes. Ground nesting, nest simple sparsely lined
with vegetation or marine mollusk shell fragments. Typical clutch three
eggs. Eggs light buff, not heavily spotted. Incubation 22-23 days,
fledging in 28-35 days. Young may remain with parents for an additional
2-3 months, but unlike other terns this species departs from nesting
sites early.
Current Population
Western
North Atlantic population (S.
n. aranea)
SE
United States 3,019 pr. (Clapp and Buckley 1984) Bahamas
and West Indies 100-500 pr. (Chardine, et al. 2000) Central
America, (Gulf Coast) a few (Van H and Norton 1984)
Total
for Western North Atlantic (S.
n. aranea): 3,100-3,500 pr.
Others
estimate total North American population at 5,400 individuals
(Spendelow and Patton 1988) to 6,000-8,000 adults (Kushlan, et al.
2002), but these figures include another subspecies represented by
western and Pacific coast populations. Old world population (yet
another subspecies) estimated at 24,000 individuals (Moller 1973).
West Indies
Location
Country
Breeding Sites
Breeding Pairs
Abaco
Bahamas
1
0
Berry Islands
Bahamas
2
0
New Providence
Bahamas
1
2
Eleuthera
Bahamas
1
0
Cat Island
Bahamas
5
64
Exumas
Bahamas
3
11
San Salvador
Bahamas
1
5
Rum Cay
Bahamas
3
21
Long Island
Bahamas
4
31
Ragged Islands
Bahamas
2
12
Mayaguana
Bahamas
1
0
Great Inagua
Bahamas
1
1
Middle Caicos
Turks and Caicos
1
10
Camaguey
Cuba
2
78
Beata
Dominican Republic
1
0
Southwest Mainland
Puerto Rico
1
0
St. Thomas
USVI
1
1
Anegada
BVI
1
4
Salt Lakes
Anguilla
1
1
Salt Lakes
Antigua
1
0
Margarita
Venezuela
2
2
Total
36
243
Conservation Status
Not
an abundant species in North America or the West Indies. It is designated as a species of
conservation need at various levels of concern by a number of US states.
Considered as Critically Endangered in the West Indies region
(Schreiber and Lee 2000). Extirpated from Beata, Puerto Rico, several places in The Bahamas, and probably
Anegada. Nests are susceptible to predation by rats at most sites, but they are rarely monitored. Buden (1990) reported predation by rats at a set of nests that he monitored on Rum Cay.
Conservation Needs
A
survey of the entire Bahamas would give needed information as to the
actual size of that population. Currently it is estimated that the
Bahamas has as much as 60% of the total population for the region.
Removal of exotic plants and animals from documented nesting cays would
improve hatching success and help reestablish open sand flats and
secondary dune habitats. Gull-billed terns would be a good species for
which to count adults foraging during baseline and future assessments
at sites where eradications are conducted.
Appropriate
signage at all know nesting sites will help to avert unintentional
disturbance of nesting birds. Human disturbance around nests
is
the major source of nest failure. Disturbance of young causes early
dispersal from nests and subsequent loss from exposure to weather and
predators. The control of Laughing Gulls at some sites may be
appropriate.
Birds
once disturbed will shift colony sites, making it difficult to locate
the “new” colonies, provide site protection from year to year, and to
monitor populations. Birds can move to new sites in the same nesting
season or subsequent ones. In most cases these sites are less
favorable. Protecting existing sites from disturbance and development
is the best conservation option.
Like
the Black Noddy, this species is in desperate need of regional
protection and possibly management in the area, but because of the
scattered nature of their nesting and the fact that many sites probably
support only a few pairs, most sites will not be in a position to
receive adequate protection. Perhaps efforts should focus on educating
and training people who frequent areas around nesting sites (fishermen,
recreational boaters, nature tour leaders) to act as voluntary wardens
to oversee nesting sites and to monitor breeding activity.
Our
knowledge of this species could increase if an index of breeding pairs
to the number of flying birds in an area could be developed. Such an
index would require a study with counts of the flying birds combined
with intense searching for nest sites through often rough terrain.
At
present, most estimates are merely reports that the birds frequent an
area and nests are almost never found and counted. For example, the
population is currently unknown on Great Inagua -- the second largest
island in the Bahamas -- but there could be hundreds of pairs given the
huge area and many lakes.
Photos
Selected References
Buden, D. 1990. The birds of Rum Cay. Wilson Bulletin 102(3): 457-468.
Clapp,
R. B. and P. A. Buckley. 1984. Status and conservation of seabirds in
the southeastern United States. Pages
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.
Chardine,
J., R. D. Morris, J. F. Parnell, and J. Pierce. 2000. Status and
conservation
priorities for Laughing Gulls, Gull-billed Terns, Royal Terns and
Bridled Terns in the West Indies. Pages 65-73 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., et al. 2002. Waterbird Conservation for the Americas:
the
North American Waterbird Conservation Plan, Version 1. Waterbird
Conservation for the Americas, Washington, DC, USA. 78 pp.
E.
A. Schreiber and D. S. Lee (eds.) 2000. Status and Conservation of West
Indian Seabirds. Society of Caribbean Ornithology, Special Publication
Number 1. 225 pp.
Moller,
A. P. 1973. The breeding population of Gul-billed Terns (Gelochelidon
nilotica nilotica Gmel). In 1972 in Europe, Africa and
western Asia,
with a review of fluctuations during the present century. Dan.
Ornithol. Foren. Tidssk. 69; 1-8.
Parnell,
J. F., R. M. Erwin, and K. C. Molina. 1995. Gull-billed Tern (Sterna
nilotica). In The Birds of North America, No. 140 (A.
Poole and F.
Gill, eds.). The Academy of Naural Sciences, Philadelphia and the
American Ornithologists’ Union, Washington, D.C.
Spendelow,
J. A. and S. R. Patton. 1988. National atlas of colonial waterbird
colonies in the contiguous United States: 1976-1982. U. S. Fish and
Wildlife Serv. Biol. Rep. 88. Washington, D.C.
Van
Halewyn, R. and R. Norton. 1984.The status and conservation of seabirds
in the Caribbean. Pages
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. 2009. Gull-billed Tern. West Indian
Breeding Seabird Atlas
<http://www.wicbirds.net/gbte.html>. Last Updated: _____.
Date accessed: ______.
