SCOTLAND The survival of capercaillies is threatened by the stress the birds suffer when they see people.

Measurements of chemicals produced in birds under stress have shown that capercaillies suffer when approached by people even if their behaviour betrays nothing untoward.

The bird, the world’s largest species of grouse, has already been wiped out in Britain once and needs protection from human disturbance. Birds assessed by the researchers were in Germany and Switzerland but the problem will be the same for capercaillies in Scotland, the only part of Britain where they cling on.

— The capercaillie is the largest member of the grouse family

— Capercaillies are thought once to have been widespread in Britain and to have survived in England until medieval times

— Because of hunting and habitat loss the last disappeared from Scotland in 1785. The species was reintroduced in the 19th century

— Numbers have crashed in Scotland from 20,000 in the 1970s to about 2,000 today. In 1999 just 1,000 were left but conservation led to a recent recovery

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