Birds at risk

Your report (9 April) that five barnacle geese will be followed by satellite to gauge wind-farm impact. This is supposed to help in the safe siting of wind turbines in the Firth of Forth and elsewhere.

The location of the wind farm in question has been determined already, and is a function of water depth, shipping routes, connections to the grid and other such constraints. There is little margin for change to accommodate migrating birds, and all we may expect as a result of the bird study is the symbolic displacement of a few turbines in the plan. But the study is interesting in that it reveals the shortcomings of the science that deals with wind-farm impacts on wildlife. For migrating birds do not always follow narrow corridors: much depends on the topography, plus wind strength and direction. Over water, they have no reason to stick to corridors, and away at sea, they could not see them if they wanted to. Besides, it saves them energy to not fight the wind, letting it alter their flight instead. Flight paths, as a result, vary from year to year, as influenced by weather systems and the resulting wind direction and speed.

Other factors that render futile any attempts at predicting flight paths are fatigue and visibility.

When their journey over the sea has been long, the birds may reach the coast after dark, or be too exhausted to gain altitude or otherwise avoid a large wind farm lying across the way. This is when we may expect significant mortality from the hundreds of spinning blades. We have evidence of wind turbines killing geese and swans in Germany.

MARK DUCHAMP

President

Save the Eagles International

Caple, Spain