Collecting guano halfway up a cliff may not be everyone's idea of fun but it has led to the discovery of the oldest nest of a bird of prey ever recorded.
Kurt Burnham, a DPhil student at Oxford University's Department of Zoology, was part of a team that collected 20 guano samples from 13 different gyrfalcon nest sites in cliffs in central-west and northwest Greenland.
Radiocarbon dating of these samples has found that one of the nests has been in continuous use for the last 2740-2360 years with three other nests likely to be over 1000 years old. The team report their findings in the journal Ibis.
The nests themselves are little more than depressions or scrapes in rock ledges but the guano deposits reveal the long history of the birds' occupation.
'When analysing multiple samples from the same nest it was also possible to detect changes over time in the type of prey consumed, very likely an indicator of changes in the prey composition in the area,' Kurt told us.
'This study provides both information on the likely initial colonization of these areas by gyrfalcons in addition to probable paleoenvironmental conditions at the time and patterns of glacial retreat. '
So what makes the falcons return year after year?
Kurt told BBC News Online: 'Something, be it nest ledge depth, or the amount of cliff overhang above the nest, is so attractive at these locations that gyrfalcons are re-using them for thousands of years.'
But, as he explains, this attachment makes them vulnerable to climate change.
'As a result of a warming and ameliorating climate other bird species, such as peregrine falcons, are moving further north.'
'As peregrine populations continue to increase in density they will likely use more and more of these traditional gyrfalcon nests, forcing gyrfalcons to find alternate locations to nest in which may not offer the same amount of protection from the harsh Arctic environment in Greenland.'
More in this Telegraph article.