Continued from The Great Bustard and its Reintroduction to the UK
The Great Bustard is the the World's heaviest flying
bird. The male bird weighs up to 18 kilograms.
An adult male measures almost 4 feet from the end
of its tail to the tip of its bill. The span of its wings is up to
260 cm and the bird reaches a height of around 104 cm, standing as high
as a roe-deer. The female Great Bustard is much smaller, being up
to 8 kg in weight and around half the size of the male bird.
The bill is of average size, but can seem to be
more lengthy than it actually is, due to the bustard's particulaly flat
The neck of the bustard is quite thick, and both
the head and neck are light gray, the back being an attractive brown and
black. The underparts are of a white colour. The secondaries
and greater wing-coverts are white, which creates a striking contrast with
the black primaries when the bustard is in flight. The ear-coverts
of both genders are quite long, which is probably where the Otis
part of the bird's scientific latin name is derived from. The
male has a long tuft of conspicuous bristly white feathers which sprout
from both sides of the base of the mandible.
One particularly conspicuous characteristic of
the Great Bustard's appearance is the existence of a pouch or gular sack
which opens below the tongue. This curious peculiarity was first identifid
by the Scottish Physician James Douglas, and was publicly announced in
1740 by the English naturaist Eleazar Albin. However, even 60 years
prior to this, physician Sir Thomas Browne MD made some indication of the
existence of this feature. It was once believed that the pouch served
as a water container from which the bustard could drink, or supply its
fellow birds with drinking water when in dry areas. This idea has long
been discarded and it is now understood that the male Great Bustard uses
this pouch in its mating display. During the male's display the pouch
is inflated and the thin wisp-like feathers which cover the pouch stand
up on end.
The existence and structure of this gular sac varies
depending on the species of bustard. For example, Garrod's researches in the 19th
Century showed that in the Australian Bustard (Ardeotis australis),
rather than having a sack or pouch, the bird simply possesses a highly
dilated oesophagus, which can be expanded in size at the Bustard's will,
giving much the same effect and appearance as the sack of the Great Bustard.
The Bustard and Breeding Season
The thickness of the male bustard's neck is particularly
evident during the breeding season. During this period the bustard
makes an effort almost as impressive as some of the courtship
displays of the Bird of Paradise. The male bustard is polygamous and
usually carries its tail in an upward attitude during the breeding season.
During courtship the tail is turned forwards whilst the male draws his
neck and head rearwards along his back, lowering his wings at the same
time and erecting the shorter feathers. In this position the he looks
very odd to us humans (although I guess it must be highly attractive to
the female bustards), as the neck, head are all virtually buried among
the erect feathers, and the male bird's breast sticks out extraordinarily.
During the height of the breeding season the male bustard has a streak
of deep brown (or a claret-like colour in some birds) which runs down from
each shoulder, forming a wide collar on his breast.