Satellite tags have told us a lot about osprey migration.
After making the return journey from their wintering grounds in Africa, ospreys start to arrive back in the UK from late March onwards.
Male ospreys get here first and start to set up their breeding territory, near lakes where they can catch a supply of fish to eat, while waiting for a female to arrive. The pair then makes its nest in a tall tree, and by late April the female has usually laid 2–4 eggs.
The young can fly about 50 days after hatching, but they depend on their parents for another month or so.
Females start the return migration, followed by males and then young. After crossing the English Channel, they travel down through France and Spain into North Africa. Some then cross the Sahara Desert directly, while others follow the West African coastline. Most of our ospreys spend the winter in West African countries such as Senegal, though ospreys from Eastern Europe may travel as far as South Africa.
Ospreys travel by day, using thermals to gain height over land. They migrate more slowly than many birds, stopping at favourite feeding sites along the way – sometimes for a week or so. Each bird travels alone and follows its own route.
Scientists who satellite-tracked ospreys from Sweden found that some reached Africa through Spain, others crossed the central Mediterranean via Italy and one went east via the Red Sea. These birds travelled an average distance of 6,7000 km (4,200 miles) at a rate of roughly 260 km (162 miles) per day, taking an average of 45 days to complete their journeys.