In the forests of the Haute-Savoy region of the French Alps, a Swiss biologist forces his way through the snow-covered branches and bushes.
Adrian Aebischer works at the University of Berne and is on one of his frequent field trips to check on a particular bird he is studying. Today he is trying to find Linos, an Eagle owl.
Like many others, this nocturnal bird of prey can easily travel far from its place of birth. Indeed, Linos was born in Switzerland and has migrated to the French side of the border.
For nearly 12 months, the owl has been followed. Last spring it was equipped with a miniature satellite tracking transmitter. The French company CLS operates the Argos system which can locate and collect data from any mobile carrying such a transmitter wherever it may be on the planet's surface.
"Linos is hiding in the bushes somewhere here, he's surely seen us already," whispers Aebischer as he scans the surroundings with a small hand-held antenna and receiver indicating in which direction is the owl. The strength of the beacon's signal gives an indication of the distance.
"The satellite positions, which have a precision of some 200 metres, are given to us via the Internet. When we see the changing position of the beacon we know a bird is alive. We often come to check the natural surroundings in which it is living."
But sometimes the plots on the computer screens do not move for several days. The ornithologists then get worried and a field excursion is necessary to discover what has happened.
The University of Berne has thus been able to gather statistics and evidence on a frequent cause of mortality of the Eagle owl: electrocution. Studies and liaison with the Swiss electricity companies has led to the isolation of a number of pylons in nesting areas and on migration routes.
Adrian Aebischer has been using the Argos beacons for several years. He is today following some 40 birds equipped with the miniature Argos transmitters which weigh only a few grammes. The more complex beacons, powered with solar cells, cost some €2000 and can provide not only a bird's position but also its body temperature and heart rate.
At the Fribourg museum, another bird is being fitted out. "Anipa is a Snowy owl which lives not only in Europe but across North America," says fellow ornithologist Michel Beaud.
Anipa is firmly held, its big bright eyes seeming to say that it does not like the ordeal. "We attach the beacon like a small rucksack on the bird's back. It is held in place with small straps around the head and body." But once correctly in place, the transmitter will not hinder the bird.
"We understand a lot about the life of the Harfang snow owl when it nests in the frozen North," says Adrian Aebischer, showing a display of one bird's movements across Greenland.
"But once winter arrives we know practically nothing. Satellite tracking is the only way to establish migration habits. The Argos system is truly an extremely valuable tool to study the movements and lifestyles of different bird species."
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