On Monday, weather conditions were good and Sacha Dench took to the air over the vast Russian tundra, for the start of her 7000 kilometre journey.
As Dench and her team from the British Wildfowl & Wetland Trust track the Bewick's swans' progress, she'll be stopping along the way to talk to people who live close to the birds' route.
She's hoping they might provide some explanations for a mystery scientists have as yet been unable to fully unravel: the Bewick's swans' decline in Europe.
The number of Bewick's swans that overwinter in Europe has been falling rapidly since 1995. In the Netherlands, the swans are now one of the species that feature on the Natura 2000 list because of the decline.
It's one of the reasons why NIOO-researchers are studying the swans' migration patterns. This winter, the researchers will track dozens of swans using special high-tech transmitters manufactured on 3D-printers.
A number of swans will also be given collars with unique codes that will make it easier to report sightings.
These sightings, explains NIOO-researcher Rascha Nuijten (department of Animal Ecology), could be of vital importance in establishing what has changed compared to twenty years ago. In the Netherlands and elsewhere.
"We use them to make population and distribution models. These models allow us to calculate possible changes in the Bewick's swans annual survival rate, breeding success and winter distribution area."
The researchers are also trying to establish the possible causes of such changes. "Think of climate change and changes in land use, for instance."
Weather permitting, Sacha Dench should make a stop over in the Netherlands some time in November - in the Lauwersmeer, formerly a key area for the swans. On www.flightoftheswans.org, it's possible to track her journey by satellite.
More details about the Bewick's swan research of Rascha Nuijten and her NIOO-colleague Bart Nolet can be found on this page and in this article.