Outdoors: The Cairngorms region is the stronghold of the Scottish ptarmigan

In winter, icy winds whip across the land like a piercing blade, and while the climate is more forgiving in summer, it can still be a bitterly cold place and snowfall is not uncommon.

On this stark landscape lives a highly specialised community of plants and animals and none is more remarkable than the ptarmigan. It is a truly special bird living in a sub-arctic environment, its plumage changing with the seasons, merging and matching with the surroundings.

The ptarmigan is a relic of the last Ice Age and is one of our few birds that can be classed a real specialist of the arctic-alpine zone. It is also a bird that is prone to giving the unsuspecting hillwalker something approaching a heart attack: sitting tight and invisible until the last second before exploding airborne at the walker's feet in a clatter of wings.

It also makes itself known to the dedicated Munro bagger in other ways. In the thick swirling mist that shrouds the high tops so frequently, many hillwalkers will be familiar with the rather eerie experience of the enveloping blanket of grey silence being broken by a hoarse, frog-like croaking. Is it one bird, or two or three? It is hard to tell, but the call of the cock ptarmigan appears to be all around and is always difficult to pinpoint.

The Cairngorms region, with the largest single area of ground above 2,500ft in Scotland is the stronghold of the Scottish ptarmigan, a member of the grouse family. The high ground here favours the growth of heath plants which are the ptarmigan's main food. In the more oceanic climate of Sutherland, it is found at altitudes of only 600ft where the strong prevailing winds on exposed lower ground create suitable habitat.

The ptarmigan eats the leaves and shoots of arctic-alpine plants, as well as insects in the summer. The crowberry is important and ptarmigan feast on their glossy black fruits in late summer. Blaeberry is another favoured food plant as is heather.

In winter the ptarmigan turns almost completely white, but its spring and summer plumage is a more cryptic mottled grey, brown and white. The feet of the bird are completely feathered, which not only prevents heat loss, but acts as a handy pair of snow-shoes in winter.

Given its very specialised habitat requirements, the ptarmigan is seen by many as a flagship indicator for change in the health of our fragile mountain environment. The bird is certainly vulnerable to the threat of over-grazing by sheep in some areas, reducing the food plants that it depends upon.

Recently, the ptarmigan disappeared from its most southerly outlier on Goatfell in Arran, with some blaming climate change.

However, the scientist Dr Adam Watson, who has studied the ptarmigan since 1943 and is a foremost authority on the bird, says it is extremely doubtful that climate change is to blame.

"The loss of birds on Goatfell has attracted attention but this was a small isolated population. Small groups on isolated small hilltops are vulnerable to extinction from time to time due to natural cyclical fluctuation," he says.

Human activity has caused localised losses, especially at Cairn Gorm since the late 1960s when an influx of crows to the high ground attracted by the food scraps left by summer tourists resulted in increased robbing of ptarmigan eggs. This was exacerbated by losses when birds died after flying into ski-lift cables.

Watson says: "These are all local impacts, but there is no evidence from field work or scientific publications that Scottish ptarmigan have been affected adversely by global warming during the last few decades."

This article was first published in The Scotsman on Saturday, 21 August, 2010b