Taxonomy
The grey crowned crane is closely related to
the black crowned crane, and the two species have sometimes been treated
as the same species. The two are separable on the basis of genetic evidence;
calls, plumage and bare parts, and all authorities treat them as different
species today.
There are two subspecies. The East
African B. r. gibberishes (crested crane) occur in the east of
the Democratic Republic of the Congo and in Uganda, of which it
is the national bird represented in its national flag,
and Kenya to eastern South Africa. It has a larger area of bare
red facial skin above the white patch than the smaller nominate
species, B. r. regulorum (South African crowned crane), which breeds
from Angola south to South Africa.
Description
The grey crowned crane is about 1 m (3.3 ft)
tall, weighs 3.5 kg (7.7 lbs), and has a wingspan of 2 m
(6.5 ft). Its body plumageis mainly grey. The wings are predominantly
white, but contain feathers with a range of colors. The head has a crown of
stiff golden feathers. The sides of the face are white, and there is a
bright red inflatable throat pouch. The bill is relatively short
and grey, and the legs are black. They have long legs for wading through the
grasses. The feet are large, yet slender, adapted for balance rather than
defense or grasping. The sexes are similar, although males tend to be slightly
larger. Young birds are greyer than adults, with a
feathered buff face.
This species and the black-crowned crane are the only
cranes that can roost in trees, because of a long hind toe that can grasp
branches. This trait is assumed to be an ancestral trait among the
cranes, which has been lost in the other subfamily. Crowned cranes also lack a
coiled trachea and have loose plumage compared to the other cranes.
Distribution and habitat
It occurs in dry savannah
in Africa south of the Sahara, although it nests in somewhat
wetter habitats. They can also be found in marshes, cultivated lands and
grassy flatlands near rivers and lakes in Uganda and Kenya and as far south as
South Africa. This animal does not have set migration patterns, and
birds nearer the tropics are typically sedentary. Birds in more arid areas,
particularly Namibia, make localized seasonal movements during drier periods
Behavior
The grey crowned crane has a breeding display involving
dancing, bowing, and jumping. It has a booming call which involves inflation of
the red gular sac. It also makes a honking sound quite different from the
trumpeting of other crane species. Both sexes dance, and immature birds join
the adults. Dancing is an integral part of courtship, but also may be done at
any time of the year.
Flocks of 30-150 birds are not uncommon.
Diet and feeding
These cranes are omnivores, eating plants,
seeds, grain, insects, frogs, worms, snakes, small fish and
the eggs of aquatic animals. Stamping their feet as they walk, they flush out
insects which are quickly caught and eaten. The birds also associate with
grazing herbivores, benefiting from the ability to grab prey items disturbed
by antelopes and gazelles. They spend their entire day looking
for food. At night, the crowned crane spends its time in the trees sleeping and
resting.
Breeding
Grey crowned cranes time their breeding season
around the rains, although the effect varies geographically. In East Africa the
species breeds year-round, but most frequently during the drier periods,
whereas in Southern Africa the breeding season is timed to coincide with the
rains. During the breeding season, pairs of cranes construct a large nest;
a platform of grass and other plants in tall wetland vegetation. The
grey crowned crane lays a clutch of 2-5 glossy, dirty-white eggs, which
are incubated by both sexes for 28–31 days. Chicks are precocial, can run
as soon as they hatch, and fledge in 56–100 days.
Status and conservation
Although the grey crowned crane remains common
over some of its range, it faces threats to its habitat due
to drainage, overgrazing, and pesticide pollution. Their global
population is estimated to be between 58,000 and 77,000 individuals. In 2012 it
was uplisted from vulnerable to endangered by
the IUCN.
Symbolism
The grey crowned crane is the national bird
of Uganda and features in the country's flag and coat
of arms.
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