anhinga [an' hin guh an' hin guh]
This large bird with a long S-shaped neck and
a long pointed bill has an average body length of
33 inches, a wingspan of 46 inches, and weighs
just under 3 pounds. The head is small and
appears to be merely an extension of its neck.
The wings are broad, allowing it to soar, and the
feet are webbed to facilitate swimming. The
physical structure of the legs allows the bird to
come onto land and climb bushes and trees. The
tail is long and is used for providing lift,
steering, braking, and balancing. When spread in
flight, the tail resembles that of a turkey. The
overall body shape of the anhinga resembles that
of a cormorant, but the hunting action of the
head and neck is more similar to a heron.
Males have greenish-black plumage overall,
accentuated by silver-gray feathers on the upper
back and wings that are edged with long white
plumes. They also have black crests. Females are
brown with a lighter brown head and neck;
juveniles are a uniform brown color.
Molting of all flight feathers at the same
time renders them flightless for a while. Unlike
other aquatic birds, all of the body feathers
become completely wet upon contact with the
water, allowing them to dive through the water
more easily. This feature, however, causes them
to have little buoyancy, to lose heat quickly,
and hinders flight.
There are two geographically distinct
subspecies of anhinga. The northernmost
distribution of Anhinga anhinga leucogaster
is found in the United States from North Carolina
to Texas, although it has been spotted as far
north as Wisconsin. Its range also includes
Mexico, Central America, Panama, and Cuba. The
individuals found in the more northern areas of
the United States migrate there in March and
April and stay until October, then return to
Mexico and more southern parts of the United
States. Anhinga anhinga anhinga is found
in South America from Colombia to Ecuador, east
of the Andes to Argentina, and in Trinidad and
Tobago. The range is limited by cool temperatures
and low amounts of sunshine.
Both subspecies prefer freshwater and coastal
aquatic habitats that include shrub or
tree-covered islands or shores. These habitats
include lakes, marshes, swamps, mangrove swamps,
shallow coastal bays, and lagoons.
Anhingas prey primarily on fish, but their
diet can also include aquatic invertebrates and
insects. Although not particularly fast swimmers,
they are effective aquatic hunters, relying on
their quick necks and sharp bills to catch prey.
They target slower-moving species of fish and
stalk them underwater, finally striking out with
their long neck and spearing the prey with the
beak. They then bring the prey above water and
manipulate it in order to swallow the fish head
Breeding can occur throughout the year, but is
usually triggered by wet or dry seasons.
The male begins courtship by soaring and
gliding, followed by marking a possible nest
location with leafy twigs. Then he performs
behavioral displays to attract the female. Once
the pair is formed, the male gathers nesting
material, while the female builds a platform
nest, which is usually on a branch overhanging
water or in open areas in the tops of trees. The
female constructs the nest by weaving sticks
together and padding it with live twigs and green
leaves. Males defend any threats to nesting
territories with extensive displays and even
fighting. Females are less aggressive, but will
defend the nest if necessary. Once formed,
breeding pairs are monogamous, and may reuse
nests from year to year.
The female lays one egg every one to three
days, until she has a clutch of two to six eggs;
average clutch size is four eggs. The oval-shaped
eggs are bluish-white or pale green, sometimes
with brown speckles. Both parents share in
incubating the eggs for 25 to 30 days.
Upon hatching, anhinga chicks are naked and
helpless. They eventually grow a white down on
their belly side and a dark down on their back
side. At first the parents feed the chicks by
dripping fluid and regurgitated material from
partially digested fish down their throats. As
the chicks grow older, they shove their heads
down the parents' beaks to get this food
material. The chicks are in the nest
approximately three weeks, but if threatened, are
able to drop into the water and swim away, later
climbing out of the water and back into the nest.
At the end of three weeks, they are able to climb
out of the nest to a branch, and fledge at
approximately six weeks. They stay with their
parents for several more weeks before becoming
Anhingas can live up to 16 years in the wild.
Anhingas start flight by either running on the
surface of the water or diving from a tree. They
usually return to the water by gliding into it
from a perch or crawling into it from land. Only
the head and neck are visible when in the water
due to their low buoyancy.
When not fishing, anhingas are usually found
perched in trees.
Similar to cormorants and turkey vultures,
anhingas sun themselves by spreading out the
wings, which dries out the plumage and absorbs
heat from the sun.
Anhingas are solitary, but are sometimes found
among groups of herons, cormorants, ibises, or
storks. Although they nest in small loose groups,
it is unusual to find them with other anhingas at
other times of the year.
Vocalizations include clicks, rattles, croaks,
and grunts. Anhingas typically call while on or
near the nest, and occasionally while flying or
perching. They are particularly silent and
elusive when flightless due to molting.
genus & species Anhinga anhina
Animal Diversity Web http://animaldiversity.org/accounts/Anhinga_anhinga/
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