Grouse have been adopting survival techniques used by mountaineers to cope with the continuing cold snap in the Scottish highlands, a bird charity has revealed.

RSPB Scotland says that grouse at its Abernethy nature reserve in Strathspey have been digging snow holes to get through the recent winter weather.

Reserve manager Desmond Dugan, who reported the phenomenon, said:  "All four species of grouse at Abernethy have been seen using snow holes during the recent snowy periods.

"Sometimes this is just a shallow depression to allow the bird to get out of the worst of the wind chill, other times it is a mini-cave where the birds spend the night under the snow and free from the biting winds and spindrift."

He added: "Up until last year we had not seen much of this behaviour.  Perhaps like our UK transport systems, our grouse have become soft and have not needed this survival technique during milder winters.

"However with the recent run of severe temperatures and snowy winters, grouse behaviour has had to adapt to the Arctic conditions. It just shows how amazingly resilient our birds can be."

Abernethy is the RSPB's second largest reserve in the UK and all four British species of grouse can be found there -  red grouse, black grouse, ptarmigan and capercaillie - as well as a wide range of other rare Scottish birds including the crested tit, Scottish crossbill, dotterel and golden eagle.

Ptarmigan, which live high up in the mountains, are well known for their ability to keep stomping in their snow holes to prevent them being snowed in during severe snow storms.

Snow holes are easily recognised by the piles of droppings left overnight or by the angel-like wing patterns formed in soft powder snow as birds take off in the morning.

Bird watchers say what makes the Abernethy reports interesting is that the ptarmigan's behaviour has been seen so widely during the cold snap in other types of grouse.