Capers are a beleaguered species and need all the help they can get during the breeding season

RSPB warden Richard Thaxton

The male birds select a clearing in the woods know as a "lek", bristle their feathers and emit a special mating song.

The Royal Society for the Protection of Birds, supported by Scottish Natural Heritage and wildlife tour operators, have drawn up a new code of conduct to give the aggressive birds a wide berth.

Instead of creeping into the morning pine forests to try to see the birds, twitchers are being urged to visit the RSPB osprey visitor centre at Loch Garten, near Aviemore.

The elusive capercaillies can sometimes be seen from the special hide and CCTV cameras.

A capercaillie in full voice

For the next four weeks the centre will open specially early from 0500BST-0800BST.

Loch Garten RSPB warden, Richard Thaxton, said: "At this time of year capercaillies can sometimes be seen lekking from our Osprey Centre and picked up on our cameras in place to watch the ospreys.

"We hope that birdwatchers visiting the area will exercise restraint and instead of looking for capercaillie elsewhere, will try the Osprey Centre instead.

"Capers are a beleaguered species and need all the help they can get during the breeding season.

"Unfortunately there are some things such as wet weather that we have no control over, but giving them as much peace and quiet as possible when they are lekking or mating is something that we can all help with."

Loch Garten, where the osprey hide is located

Part of the forest around the osprey centre has been sealed off with a temporary barrier during the early hours of the morning.

The capercaillie is big enough to be nicknamed the "horse of the woods" and was hunted to extinction in the late 18th century.

It was re-established in 1837 when the Marquis of Dunblane brought 50 birds from Sweden, but now it is confined to central and north-east Scotland.

However it is now in dramatic decline, with loss of pine forest habitat being blamed along with high deer fences that the low flying birds collide with.

The mating song of the male has been described as beginning with a resonant rattle, continuing with a pop-like a cork being pulled from a wine bottle, followed by the pouring of a liquid out of a narrow-necked bottle and ending with the sound of knife grinding.

The males can be very aggressive and have been known to attack deer, dogs, sheep and even humans if they are disturbed.