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Using
high-tech radio tags costing USD 3,000 apiece, Hungarian biologists follow
imperial eagles by satellite to find the culprits responsible for their
threatened status. — By Greg Spencer
In an explosion of twigs and feathers, the panicked raptor springs from the nest and takes flight over a field of sunflowers. Though just 10 weeks old, this chick appears full grown;its wingspan easily stretches two metres. But despite his energetic flapping, he's a novice at flying and crash lands in the sunflowers about 200 metres away. Two of Demeter's colleagues, sprinting and bushwhacking their way through the bristly, chest-high flowers, quickly locate the grounded eaglet and bundle him up in a t-shirt. As is usual in these cases, the bird is too frightened to put up much of a struggle; he's literally scared stiff. Still, the biologist carrying the eagle, Andras Kovacs, maintains a firm grip on the bird's legs, having heard the horror stories of colleagues who have had hands pierced by a raptor's razor sharp, vise-like talons. Mixed feelings The biologists on today's mission have mixed feelings about such invasive work, particularly considering the delicate status of the imperial eagle (Aquila heliaca), of which fewer than 3, 000 breeding pairs exist in the world. But to preserve the species, scientists need to know where they're being killed and by what. The imperial eagle presents formidable geographic challenges, as it ranges all the way from Hungary and Slovakia, south to the Balkans, and eastward into Central Asia. And although the birds stick close to their breeding grounds as adults, they travel widely as juveniles. Chicks banded in Hungary, for instance, have turned up as juveniles in Greece and Bulgaria. Tracking the routes they take to such distant locales was previously all but impossible. But new satellite technology has enabled biologists to track migratory animals over thousands of kilometres. Demeter and his colleagues at the Hungarian Ornithological and Nature Conservation Society (MME)are conducting a EUR 560, 000, European Union Life project for the preservation of the imperial eagle. Some 70 breeding pairs exist in Hungary and about 35 more live in neighbouring Slovakia;together they make up more than 60 percent of imperial eagles remaining in Europe outside the former Soviet Union, according to MME. The project relies on conventional radio telemetry to map out the habitat of the species as well as newer satellite technology. The Hungarian team began their project in July by tagging two chicks with conventional radio transmitters whose signals can be picked up by a special receiver up to 60 kilometers away. This technology has enabled the researchers to track the birds' movements around their Hungarian nesting sites, most of which lie in the northern part of the country. Juvenile gave clues "We want to compare land-use patterns and the preferences of eagles, so that we can predict how expected land-use changes after joining the EU could influence the imperial eagle population in Hungary," Demeter said. "We haven't managed to capture and tag an adult yet. But thanks to the chicks we have already gained useful information about the parents' territories. Because the juveniles spend several weeks with the adults after they learn to fly, the tagged juveniles on several occasions have led us to the adults." In one case, Demeter explained, a tagged juvenile gave clues as to his parents' hunting grounds, which had until then been a mystery. No one can predict the sum impact of EU accession on regional wildlife, but this seems certain:less land will be devoted to agriculture, and the land that remains under cultivation will be farmed much more intensively. This will take foraging space from hares, hamsters and ground squirrels, the eagles' favourite prey. "If you look at the flora and fauna of Western Europe and the flora and fauna of Eastern Europe, it's clear there's more here," said Marton Horvath, a zoologist working with Demeter on the eagle project. "For instance in Spain, there are fences all over, maybe 20 per kilometre. You can't feel free in an environment like that and it's not good for wildlife, either." Though agriculture is certain to be restructured, EU legislation offers protective land designations that may help mitigate harm to the eagles. MME hopes to use the information gleaned from its radio tracking to put eagle habitat into special protection areas, or SPAs. These sites would be part of the EU's Natura 2000 Network, where human activity is allowed, but restricted in specific ways to safeguard protected species. András Kovacs, a project officer in charge of EU accession matters, admits to doubts about the effectiveness of special protection areas. In Western Europe, he said, enforcement of the Birds and Habitats Directive has been insufficient, prompting the EU to sue several national governments. Nevertheless, Kovacs is pressing forward with documentation to extend several proposed SPAs in Hungary in preparation of the country's entry into the EU. The focused research on the birds' home territory is just one aspect of the eagle project. The other crucial aspect involves mapping the long migrations of juvenile birds to wintering sites and places where they like to congregate for hunting and resting. Some 60 to 90 percent of imperial eagles are believed to die during their first few years, according to MME. Greece is believed a popular wintering site for juvenile birds, but little is known about other sites, or how the birds get to them or where and for how long they stopover along the way. Absent such information, preservationists can't take legal steps or conservation measures to address the hazards that are killing the young eagles. To begin filling the knowledge gap, Demeter and his colleagues recently acquired some state-of-the-art satellite tags which allow them to track the birds wherever they fly in the world. The special transmitters, slightly smaller than a cigarette package and costing USD 3, 000 apiece, send out signals that can be picked up by the Argos satellite system, an international enterprise dedicated to climatic and environmental research. The satellites, which have also been used to track the movements and even heart beats of such creatures as wolves, sea turtles and geese, can pinpoint a transmitter's location within 300 metres. Huge tag The new transmitters slightly exceed two percent of the birds' body weight, whereas one percent is considered ideal. Out in the field, after climbing a tree to return a tagged eagle to its nest, Demeter expressed concern. "The tag is huge," Demeter said. "But that's where satellite technology is at the moment. But at least he'll have time to get used to it in the nest." A month later, results were mixed. MME had collected readings on both the birds that were tagged in August. The first chick was apparently behaving normally, sticking close to its nesting site in northern Hungary with its parents. However, the second eaglet somehow blew off course, first to Romania and later to a spot north of Belgrade, where transmissions ceased. Demeter theorised that it had flown too high and was caught by a strong north-western wind. The fact that the transmissions stopped likely meant it had died. "The fact that he left his parents relatively early reduced his chances," Demeter said. The research is in its early days and doesn't guarantee results. Although the transmitters have battery power for two years, potential pitfalls are many for young eagles. But conventional telemetry done on the Spanish cousin of the imperial eagle, Aquila adalberti, produced results that the Hungarians hope to emulate. In that case, researchers located a site where eagles were being electrocuted by transmission poles. A follow-up conservation project focused on insulating the most hazardous poles, and in the end the mortality of juvenile birds dropped drastically. Like their Spanish colleagues, the Hungarian team would like to improve the chances for eagles during the most vulnerable periods of their lives, including that between the laying of eggs and the fledging of the chicks. "The greatest pleasure is when you see them fly with their parents for the first time," Demeter said. |
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