More vultures at risk

LAST year I wrote about three species of Asian Gyps vulture that risk extinction because of their acute sensitivity to diclofenac, ingested from the carcasses of cattle treated with the drug (PJ, 22 October 2011, p515).

But these are not the only endangered vultures. The griffon vulture, Gyps fulvus, which is the sole representative of the genus in Europe, is also dying in large numbers, not by poisoning but killed by collision with wind turbines and power cables.

The vulture’s main European stronghold is Spain, which has a large programme of wind turbine installation. More than 1,000 vultures are killed each year by Spanish turbine blades.

Since all large raptors have keen eyesight, the number of deaths has been puzzling, But University of Birmingham researchers have found that vultures scavenging for carrion are almost blind in the direction of travel. They have heavy brows that shade their eyes from the sun but at the same time prevent them seeing ahead.

Vultures evolved their foraging strategies in a world without

man-made obstacles intruding into their airspace. As they glide along, scanning the ground below them, they expect the way ahead to be clear. They are just not equipped for the challenge posed by huge turbine installations.

The researchers believe that attempting to make turbines more conspicuous will have little effect. They suggest luring the raptors away from turbines by developing feeding stations (“vulture restaurants”) in safer areas.

But collisions with man-made objects are not the only risk faced by Europe’s griffon vultures. EU measures to prevent the spread of bovine spongiform encephalopathy (mad cow disease) have included bans on leaving cattle carcasses lying out in the open. In the Pyrenees, this ruling has critically reduced the availability of food for vultures. Although they normally feed only on carrion, starving vultures have begun attacking young or weak living animals.