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.