A natural spectacle is underway in Switzerland. Birds are migrating south for the winter and many cross the Swiss Alps on their way to wintering grounds around the Mediterranean and in sub-Saharan Africa.
It's a beautiful clear day on Lake Sempach and a woman has just arrived at the Swiss Ornithological Institute, cradling a large songbird. It's injured. She shows it to a woman working at the institute, who takes it to the bird hospital located in the basement.
A few kilometres to the east, biologist Felix Liechti sits in a makeshift hut set up behind an old military vehicle. He uses the vehicle's radar to track birds as part of a migration study.
The ornithological institute is involved in a variety of projects; from migration research, population monitoring and ecological studies, to running a small clinic for injured birds.
In the clinic, Barbara Troesch is helping nurse a buzzard back to health. It has suffered extreme weight loss, limiting its ability to fly.
"You can see that it doesn't have enough fat on its breast so it needs a few days here before it can be released," she says. "It has excellent reflexes, it responds properly. So it's fine. It just needs to put on a bit of weight."
In the makeshift hut, Liechti follows the flight of another bird of prey on his computer screen: "I guess it's a raptor from the fluctuation of the echo. The fluctuation is related to the wing beat pattern of the bird. It's gliding now, which is a typical trait of raptors. There are rarely any single wing flaps in between."
Liechti is in his element at this time of year. He has devoted his life to the study of migratory patterns, and has notched up some impressive achievements.
A year ago, he completed groundbreaking research in Israel's Negev desert, showing that migratory birds regularly fly up to heights of 9,000 metres above sea level. He discovered that they catch lower jet streams at this altitude enabling them to fly at close to 200 kilometres an hour.
He's now testing a new method to make tracking more precise. He hopes to put a combined radar and infrared system to use in the Sahara desert to fill in the missing link in migration research.
"It's one of the big mysteries of bird migrations. We know that birds fly across the Sahara but we don't know how they do it," Liechti says. "We don't know whether they fly along the coast to avoid the dry parts of the desert, or whether they fly non-stop or if they pause at the oases."
Switzerland is an ideal location for testing his new method, lying as it does at the heart of Europe's north-south migrations.
For ornithologists, the Klingnauer reservoir in canton Aargau is a particularly special place. More than 270 species have been spotted here, including various kinds of birds of prey and oyster catchers and sandpipers.
Most migratory birds pass over Switzerland in a southwesterly direction. An important resting area is the Fanel/Chablais de Cudrefin reserve on the northeast shore of Lake Neuchatel. The reserve is part of the largest marshland in the country, and offers numerous bird species a wide variety of habitats - from islands and sandbanks to ponds and meadows.
Often birds of prey like the buzzard in the clinic or the one sighted on Liechti's radar screen prefer the favourable autumn winds passing over the Gurnigel watershed near the town of Thun to take them south.
Large numbers of raptors take advantage of the thermals there to carry them over the mountain ridges to the southern side of the Alps. Concentrations of small birds including finches and thrushes can be seen following the same route, filling the sky at daybreak.
The ornithological institute tries to lead conservation efforts by example. Visitors to the centre can follow an outdoor trail that the institute has tried to return to a natural state.
Felix Tobler of the institute points with pride to an area of the Sempach shoreline replanted with reeds. "We started it two years ago. We're trying to bring new life back to the lake shore," he says.
The water quality of the lake deteriorated dramatically in the second half of the 20th century, causing the disappearance of plant life. There's new hope now that the water has improved. "It's a pioneer project," Tobler says. "We have to see what's going to happen. There's no data available on how the water quality affects these plants."
The effort has at least paid off in persuading two colonies of grey herons to breed on the shore. Swiss conservationists have been fighting a long battle to preserve wetlands, with some success.
Tobler says they're also trying to work with farmers to attract species back to rural areas. The institute has launched a pilot project to convince farmers to plant indigenous crops no longer in fashion. Tobler says the results are encouraging so far. In canton Schaffhausen, some converted fields provide nesting areas and food for the endangered partridge.
Inside the institute, a group of school children carry out their own study by identifying a number of migratory species. One boy holds a piece of paper and a pencil in his hand. He writes "bird of prey" above a picture of a bird's head.
Tobler helps him with his project, and points to a glass case where a stuffed buzzard reveals its impressive wingspan.
A few kilometres away, biologist Felix Liechti continues the institute's research.
"We don't really know which species we're tracking. The radar gives us the wing beat pattern and with this we can estimate the species of bird. The higher the frequency, the smaller the bird..."
Which just goes to show that the job of identifying birds, and discovering the secrets of migration, is anything but child's play.
by Dale Bechtel