THE increasingly popularity of outdoor winter sports such as skiing, hill-walking and snow-shoeing could be putting capercaillie populations under threat, according to a new study.
Researchers have found the disturbance caused by winter sports puts the birds under stress, affecting their fitness and ability to breed.
The capercaillie is Scotland's rarest bird, according to the Royal Society for the Protection of Birds (RSPB)
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Just over 1,000 breeding pairs can be found in the UK, mostly north of the Border, compared with 20,000 pairs 30 years ago.
In recent years, their numbers have also declined rapidly in central Europe. They are found in mature coniferous forests.
Researchers are now recommending that areas of forest should be kept undisturbed for the bird, which is the largest member of the grouse family and has a distinctive, rumbling call.
Working in the southern Black Forest in Germany, staff from the Swiss Ornithological Institute collected the birds' droppings before and after the ski season and found significantly higher levels of corticosterone, a stress hormone, in areas with moderate or high levels of outdoor sports tourism.
The study's author, Dr Lukas Jenni, said: "Ski tourism affects both habitat use and stress-hormone levels in capercaillie, and this could adversely affect their body condition and overall fitness.
"Because of this, we recommend that managers keep forests inhabited by capercaillie free from tourism infrastructure and retain undisturbed forest patches within skiing areas." Levels of winter sports activities had increased dramatically in the last ten years, she added, which also affected other birds, such as black grouse.
A spokesman for the RSPB agreed that the birds – which were reintroduced to Scotland in the 19th century after becoming extinct in 1785 – were very sensitive to disturbance by humans.
"Our own research has shown that they tend to nest away from paths," he added. "There are Alpine forests where you do get capercaillie in the same areas as skiers.
"But our advice to people who are interested in capercaillie is to see them in the autumn and avoid them when they're nesting."
Under the Wildlife and Countryside Act, it is an offence to deliberately disturb capercaillie.
The researchers' findings, which it is hoped will help inform conservation-management programmes, are published in British Ecological Society this week.
The full article contains 386 words and appears in The Scotsman newspaper.
