A 2,500-year-old bird’s nest has been discovered on a cliff in Greenland.
The nesting site is still continually used by gyrfalcons, the world’s largest species of falcon, and is the oldest raptor nest ever recorded.
Three other nests, each over 1,000 years old, have also been found, one of which contains feathers from a bird that lived more than 600 years ago.
However, ornithologists fear climate change may soon drive the birds from these ancient nesting sites.
Gyrfalcons live circumpolar to the Arctic. The birds range in colour from being almost exclusively white in Greenland to usually black in Labrador in Canada.
Like many falcons, they do not build nests out of sticks and twigs, but typically lay eggs in bowl-shaped depressions they scrape into existing ledges or old nests made by other birds such as ravens.
But while stick nests are often frequently damaged, preventing their repeated use, gyrfalcons will often revisit some ledges and potholes from year to year.
To find out just how long the birds return to the same site, ornithologist Kurt Burnham of the University of Oxford, UK and colleagues decided to carbon date the guano and other debris that birds leave at various nest sites around Greenland.
The cold dry climate of Greenland slows the decay of the falcons’ droppings and various nest sites had built up levels of guano almost 2m deep.
But Burnham was still surprised to find out just how old these nests are.
Carbon dating revealed that one nest in Kangerlussuaq in central-west Greenland is between 2,360 and 2,740 years old, the researchers report in Ibis.