There are only about 900 capercaillie in Scotland

Experts from Dundee University said their findings will indicate the state of the bird's health and also which habitats are most suitable.

Droppings are being collected from four Scottish habitats - an island in Loch Lomond, Abernethy Forest, Glen Tannar and Glen Morangie.

There are only about 900 birds left in Scotland.

Stress or illness

The study will look at the amount of parasite eggs in the faeces of the capercaillies, the world's largest grouse.

Parasites indicate the bird is suffering from stress or illness, which make it less likely to reproduce, the experts said.

The Capercaillie became extinct in Scotland at the end of the 19th century but was reintroduced from Scandinavia.

However since 1970, 95% of its 20,000 population has been lost and only around 900 birds now remain in Scotland, the RSPB estimates.

Unfavourable weather, poor quality ground cover, mortality from flying into deer fences and predators such as foxes and crows have all contributed.

It's easy, inexpensive and provides so much accurate and valuable information for assessing the health of populations and their ultimate habitats. Keith Skene Dundee University

Keith Skene, a lecturer in the division of environmental and applied biology in the university's school of life sciences, praised the new method as "an inspired idea".

He said: "It's easy, inexpensive and provides so much accurate and valuable information for assessing the health of populations and their ultimate habitats.

"We hope to have completed our comparative study of the four habitats by May next year, allowing us to correlate Capercaillie stress with key habitat elements.