They
have efficient digestive system
By Nutan
Shukla
SCAVENGER by nature, Old World
vultures are found in Africa, Asia and Europe. They have
been regular visitors to the bloody battlefields since
the history of wars started.It is said the ancient
Abyssinian armies were accompanied overhead by flocks of
vultures, and in another example during the Crimean War
shooting parties were sent to scare off these scavengers
because badly injured soldiers who were unable to move
and defend themselves from these birds were in danger of
being attacked and torn apart by them.
Now studies have shown
that different species of vultures have specialised in
eating different parts of the carcass. This is the reason
that despite feasting on one body these birds do not face
any competition among themselves. In East Africa it was
observed that while eating, different species follow a
strict order of feeding. On the same carcass they feed in
the order of Black vulture, then Lappet-faced, then
Griffon, Egyptian and Hooded vulture. For
example, aggressive Lappet-faced vultures prefer skin,
tendons, and other coarse tissues. In other words they
open up the body which is difficult for other species to
do. Griffon vultures have sharp-edged bill for cutting
meat and a serrated tongue to help swallow it quickly.
The crop of the bird is quite big and can take a quarter
of the birds body weight in food. They feed on the
soft and fleshy parts of the body. Species with naked
head and neck, including Lappet-faced, have the added
advantage of inserting their head inside the carcass
without spoiling their plumage. Apart from the above two
species, Egyptian vultures, who have thin beak, content
themselves with the leftovers. This order of feeding not
only avoids competition but also ensures speedy and clean
disposal of the body.
Vultures have very
efficient digestive system which is able to extract even
the last drop of nutrients from the most degraded food
source. This is the reason when these birds do not find
any carcass they take to eating dung, but not just any
old dung. Their preference is the excreta of big cats who
do not digest their food as well as the dogs do. The
result is that lions dung contain 10 per cent more
undigested food which is consumed by these birds.
Vulture chicks depend on
spotted hyenas, and such other creatures, for their
supply of calcium which is very necessary for the healthy
development of their bones. They need pieces of bones in
their food so that their body can extract calcium from
it, but unfortunately the meat regurgitated by their
parents has little calcium. In such situations parents
depend on hyenas who, with their powerful teeth and jaws,
can break up even the toughest of bones. They ignore very
small fragments which are taken up by these birds for
their young.
In the Indian
subcontinent no vulture is found beyond the southern tip
of India. While even small land birds, like the paradise
flycatcher, cross over to Sri Lanka from India, no
vulture crosses the negligible sea barrier. Only one or
two scavenger vultures have been spotted in Sri Lanka.
While these strong fliers are seen in abundance in South
India, their absence across the Palk Strait is
inexplicable.
Being heavy-bodied birds
with large wings vultures can cruise on air currents
without flapping their wings for a long time. They
utilise the up-drafts generated by warm air currents.
Ruppells griffon vulture, belonging chiefly to the
drier parts of Africa, is the highest-flying bird in the
world. In one recorded instance this bird had collided
with an aircraft at the altitude of 37,000 ft or 11,274
metres over Abidjan, Ivory Coast, Western Africa. The
incident took place on November 29, 1973. Fortunately
there was no loss of life and the plane landed safely
with one damaged engine.
Why do these birds
select such a high altitude as a flight path? The reason
suggested is thinner air allows faster flight without
much effort, thus saving precious energy. While flying at
a higher altitude vultures face almost no physiological
problem with regard to breathing. They have much more
efficient system than other living beings, including
humans. Their flow of blood enables oxygen to be
extracted from air with far greater efficiency than that
of any other vertebrate. If the flight is in a cloudless
condition, then low temperature found at great heights
too does not bother the bird.
Earlier, it was believed
that vultures had a very powerful eyesight and they could
spot a carcass from a long distance. But the fact is that
they have a reasonable good eyesight. The basis of their
modus operandi is observing other vultures. When any bird
spots a dead or dying animal or human, it flies to it in
a high speed. This activity of the individual bird
attracts its other relatives, who are also in search of
food and keep a close watch on each other.
As far as feeding order
is concerned, Ruppells vultures do not have as
strong bills as the other vultures (e.g. white-headed
lappet-faced) have. Consequently, they arrive late on the
carcass by the time other strong billed cousins tear the
tough carcass skin open. To find food source these
high-flying scavengers react to the behaviour of other
scavengers too, like jackals and hyenas.
This feature was published on May 2, 1999
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