办事指南

The eagles have landed - Satellite tracking is helping to save one of Spain's rarest birds

点击量:   时间:2017-05-17 07:02:08

By Luis Miguel Ariza Madrid SPANISH scientists have solved a long-standing mystery about the fate of the country’s endangered imperial eagles. By working out where the young eagles go after leaving the nest, they have managed to dramatically reduce the number of birds killed before they can breed. Ornithologists knew that the young abandoned their nesting areas within a year of being born, only to return several years later. But no one knew where they went during that time—or why so many died before they could breed. A team of researchers led by Javier Oria, an engineer and expert on imperial eagles (Aquila adalberti) based in Extremadura, has now completed a two-year survey in which eight eagles were tracked from their nesting areas in central Spain via satellite transmitters attached to the birds’ backs. In a separate three-year survey, they tracked 40 birds using VHF radio transmitters. After leaving their nests, the team discovered, young eagles fly hundreds of kilometres south to “dispersion zones”, where they stay until they reach sexual maturity up to five years later. When they are ready to breed, the eagles return to their nesting areas to look for a mate. “The young can travel up to 400 kilometres from the nests to live in these zones,” says Oria. In one case, the satellite picked up an eagle in Senegal. Many eagles did not return to breed, the team found, because they were killed when they flew into or landed on electricity wires in the dispersion zones. “Before the surveys, 60 per cent of the young eagles died after being electrocuted,” says Oria. Now, however, the mortality rate has dropped to 10 per cent after the local authorities moved the electricity wires out of the eagles’ flight paths. In one area, outside the Doñana National Park,