The Anhinga is the classic bird many people visualize when they think of a
swamp; a place of Spanish moss draped trees in a watery environment.
It is a bird that is frequently seen sunning itself on a snag with
wings spread and long neck outstretched.
Its behavior of frequently bobbing its neck and making primitive
calls adds to the mystique of its setting.
The Anhinga, also known as "water turkey" and "snake
bird", breeds in the freshwater river bottoms and swamps of the
southeastern United States southward to northern Argentina and Uruguay
(American Ornithologists' Union 1998).
In Texas, Anhingas forage and breed in swamps which are
frequently dominated by bald cypress.
Typical sites include Caddo Lake (32o 45' N, 94o 00' W), below Sam
Rayburn Reservoir in the "forks of the river" (30o 45' N, 94o
10' W), the "blue elbow swamp" of Orange County (300 10' N, 93o
45'W), and in the Trinity River delta near Wallisville (29o 50' N, 94o 45'
W). They also nest in river
and creek oxbow lakes and sloughs, beaver ponds, and the upper ends of
reservoirs where substantial numbers of trees still exist in the water. DISTRIBUTION: Oberholser (1974) reported the Anhinga as
occurring in most Texas river bottoms south and east of the Edwards
Plateau and Dallas. Greatest
concentrations occur in swamps, typically towards the delta of the rivers. TBBAP atlasers most frequently reported confirmed nesting
along the Sulphur, Sabine, Neches, Trinity and Brazos Rivers (all in the
eastern third of the state north of 29 degrees latitude), and two reports
each on the Guadalupe (28097 and 28096) and Nueces River (27097 and 28098)
drainages. SEASONAL OCCURRENCE: The Anhinga occurs throughout the
breeding season in low numbers in suitable swamp-like/oxbow habitats.
During spring and fall there is an abundance of Anhingas as many
thousands of birds from states to the east and local residents are
observed migrating through Texas along river valleys and the coast
"to and from" breeding grounds and their winter homes.
They can frequently be observed soaring in kettles along with
hawks, vultures and other raptors. Anhingas start forming large flocks in August and migrate
southward along rivers to the upland side of the coast and then
paralleling the coast southward throughout the months of August and
September. Anhingas
reverse their migration route in March and April.
Nesting usually starts in April and May and ends in August (Oberholser
1974). TBBAP atlasers
reported confirmed nesting from 29 May through 17 July.
Small numbers commonly over-winter in swamps and other forested
wetlands along the coast and inland as far north as Jasper.
This species seeks sunlit, wind protected openings during the
cooler months at these sites because of the water soaking tendencies of
Anhinga feathers (Owre 1967). BREEDING HABITAT:
The Anhinga is colonial and typically nests in small aggregations
along with much larger numbers of herons, egrets, ibises and cormorants.
Nests are relatively bulky, made up of sticks and other vegetation,
and situated in a fork within the canopy of live trees.
The nesting colony is almost always located over water.
A similar appearing species, the Neotropic Cormorant (Phalacrocorax
olivaceus), almost always |
positions its nests to the outside of the canopy or the
highest point of trees. Many
times the nests are located on dead snags.
Anhinga colony sites are most frequently in swamps and other
forested wetlands. STATUS: Populations of Anhingas are expected to have
declined during this century when over half of the Texas bottomland
hardwood forests were lost due to reservoir construction and land use changes (Frye 1987).
However, large scale surveys of birds were only conducted after
much of the land use changes have already occurred. They show that this
species occurs in small numbers over a broad area, but no accurate
population trends are available. The Texas Colonial Waterbird Society annually surveyed
inland and coastal colonial waterbird sites from 1973 to the present at
sites that were accessible to observers, with most inland sites being
dropped from the survey after the 1980s. Anhingas only represented a small
portion of the birds surveyed in these colonies.
No reliable trend data was obtained from these surveys because
Anhinga nests are scattered amongst hundreds of other heron/egret/ibis
nests and are generally out of view within the canopy of trees.
One of the largest concentrations reported during the surveys was
350 pairs at the Beaver-Catfish Club (31o52' N, 95o53'W)
in 1979 in Anderson County (Texas Colonial Waterbird Society 1982).
Typical sites where Anhingas nested were reported to have fewer
than 50 pairs. The federal breeding bird surveys conducted along
roadways since 1968 in Texas do not contact enough swamp habitat to
adequately survey this species. An
adequate sample for statistical trend analysis typically requires a
species to be found on at least 14 routes.
Anhingas are normally found on less than 5 routes each year (B.
Peterjohn pers. comm.). The TBBAP did not show any appreciable change from the
status at the time of Oberholser's (1974) landmark book on the birds of
Texas with exceptions in extreme eastern Texas where few birders reported
observations. Oberholser
(1974) only showed one nesting record along the Sabine and Neches River
drainages, but this was an artifact owing to few birders reporting from
the area and not from a lack of birds.
The TBBAP reported 18 quads with confirmed nesting in these two
drainages. Otherwise, TBBAP atlasers reported confirmed and probable
breeding evidence from traditional nesting areas. Text by Brent Ortego (ca. 1999) |
