According to research, just published in Ibis [the International Journal of Avian Science] by University of Birmingham,
vultures are colliding with wind turbines because they cannot see the way ahead.
Vultures are at the top of the food chain and so their
presence provides a good indication of a healthy environment. Thanks to
strenuous conservation efforts their numbers in Europe
have been increasing. They are however now, the frequent victims of collisions
with wind turbines and power lines.
In Spain,
which has a considerable programme of wind turbine installation, it is
estimated that a minimum of 1,000 Griffon Vultures die each year from
collisions with wind turbines. The reasons for these collisions have not been
explained and are especially puzzling since vultures have some of the keenest
eyes of all animals and they fly only by day. The answer seems to be that when
foraging for carrion, vultures are in fact blind in the direction of travel.
They simply do not see the turbines no matter how large and conspicuous they
may appear to us. Emeritus Professor Graham Martin from the University of
Birmingham's School of Biosciences, who led the study into why vultures are so
vulnerable, said, "It is known that large raptors have the best visual
acuity of any bird, so I wanted to investigate why so many are being killed in
wind turbine collisions. We discovered that, when in flight, vultures are often
blind in the direction of travel. This is because their visual field doesn't
allow them to see forwards when they are looking down seeking carrion on the
ground. We had thought that they would be keeping a look out ahead, but we have
found that this isn't so; they are more interested in what is on the ground and
they assume that the world ahead will be clear of obstacles.
The researchers also discovered that the extensive blind
area above the head, which projects forward when the birds look down, serves an
important function in preventing the vultures' eyes from imaging the sun.
Imaging the sun can degrade image quality across the whole retina, which would
reduce the bird's ability to detect food on the ground below. "In effect
vultures have sunshades. The enlarged brows, which gives them their
characteristic angry look, help keep the sun out of their eyes but they stop
them seeing forward when they peer down.
To mitigate the number of vulture collisions, the team
recommends the development of attractive foraging habitats away from wind
turbines. Professor Martin continued, "Wind farms and vultures need to be
kept apart. Increasing the conspicuousness of man-made structures will achieve
only marginal gains as obstacles like wind turbines will often simply not be
seen by the birds when foraging. Reductions in vulture collisions could be
achieved by providing feeding stations, or 'vulture restaurants', away from
these obstacles to stop the birds foraging near turbine installations."
Another problem for our endemic Cape Vulture.
After decades of
conservation efforts for this endemic species, the population continues to
decline. During the 2011 breeding season a total of only 2848 breeding pairs
was recorded for the season. This is a drop from the previous years of 2900
breeding pairs.
The Cape Vulture - Gyps coprotheres - is Endemic
to Southern Africa and is found mainly in South
Africa, Lesotho,
Botswana and Namibia.
A large vulture with near-naked head and neck. Adult creamy-buff, with
contrasting dark flight- and tail-feathers. Pale buff neck-ruff. Underwing in
flight has pale silvery secondary feathers and black alula. Yellowish eye,
black bill, bluish throat and facial skin, dark neck. Juveniles and immatures
generally darker and more streaked, with brown to orange eyes and red neck. The
two prominent bare skin patches at the base of the neck, are thought to be
temperature sensors and used for detecting the presence of thermals.
Calls are loud cackles, grunts, hisses and roars.
It nests on cliffs and usually lays one egg per year.
Monogamous colonial nester, breeding in colonies. They nest and roost on
cliffs and usually lay one egg per year. The nest is mainly built by the
female, consisting of a bulky platform of sticks, twigs and dry grass, with a
shallow cup in the centre lined with smaller sticks and grass. It is typically
placed on a cliff ledge, often using the same site over multiple breeding
seasons.
The breeding season is between May and June with a single egg laid, which is
incubated by both sexes for about 55 to 59 days. The chick is brooded
constantly for the first 72 days, while both parents feed it. It eventually
leaves the nest at about 125-171 days old, becoming fully independent about 15
to 221 days later.
Cape Vultures feed on carrion, searching
aerially for a carcass to feed on. They can eat 1.5kg at a sitting, which is
over 15 percent of the weight of an adult bird and can do this in five minutes.
It slices off flesh with the sharp edge of its bill eating it and storing some
in its crop, which can sustain it for about three days.
Vulnerable globally. It is regionally extinct in Swaziland
and Critically Endangered in Namibia.
Its global population has decreased dramatically, the current population is
estimated at 8,000. This is thought to have been largely caused by habitat
loss, persecution for use in traditional medicine, human disturbance of
colonies, poisoning and improvements in animal husbandry resulting in a decreased
availability of carrion.
These large Vultures can be seen on the following Aves Birding
Tours/Safaris/Adventures: -
Aves Arid Birding Tour / Safari /Adventure.
Aves Eastern Cape
Birding Tour / Safari
/Adventure.
Aves Highlands / Tembe Birding Tour / Safari
/ Adventure.
Aves KZN Birding Tour / Safari / Adventure.
Aves North East Birding Tour / Safari / Adventure.
Aves North West
Birding Tour / Safari / Adventure.
Aves Western Cape
Birding Tour / Safari /
Adventure.