In the UK capercaillie are only found in Scotland. They are part of a global population extending from Russia to Scandinavia and across Europe from the Black Forest to the Pyrenees.
Capable of reaching a grand old age of six, male capercaillie can hold huge territories in the forest. Each spring they attend lek sites; used by capercaillie for generations, to perform a display of pops, whistles and flutter jumps to attract the attention of females.
If successful at the lek, females will lay around eight eggs in May, in a nest on the forest floor and visit forest bogs to feed on protein-rich cotton grass, to stay strong and healthy whilst breeding.
Chicks will hatch from late May and be fed on a diet of insects by their mother. If we experience a wet spring insects can be in short supply. This can lead chicks to starve. Others may die of cold or be eaten by predators; typically only one chick per brood will make it to adulthood.
Making it off the forest floor and into the branches is a big step towards relative safety for chicks, who are able to fly within two to three weeks of hatching.
By September they're independent of their mother and in order not to compete for food and avoid inbreeding, they'll disperse from where they were born. Females will often travel further than males; if habitat is available they'll make a new start up to 30km away.
The State of Nature Report 2019 provides the best available insight into Scotland’s biodiversity and clearly sets out the grave threats to Scotland’s wildlife. The report confirms that one in nine species, including capercaillie, are now threatened with extinction.
Consequently one of the highest nature conservation priorities in the UK, capercaillie are also an IUCN Red List species of Conservation Concern and an Annex I species in the EU Birds Directive.
Causes of decline
Capercaillie numbers have fallen for lots of reasons including lack of habitat, low productivity, predation, collisions with unmarked fences and disturbance.
Capercaillie are a specialist species, only able to survive in a narrow range of conditions. They require extensive areas of Scots Pine dominated woodland, which is only available in Scotland, and a varied forest structure including open areas to feed and dense areas for cover.
These specific habitat needs make capercaillie particularly vulnerable to habitat fragmentation and unfavourable forest management. Limited and fragmented habitat is a recognised cause of population decline, and can lead capercaillie populations to become isolated. This can increase the likelihood of inbreeding. Less habitat means capercaillie may also be more prone to the impacts of predation and human disturbance.
New genetic research
Capercaillie numbers in the UK are now so low that the population is likely to be experiencing a genetic bottleneck. This will limit the genetic diversity of the species and in the face of climate change, this could affect the birds’ ability to adapt and survive.
To investigate this issue over 1,000 capercaillie feathers have been collected by the project from across the National Park. By analysing the DNA from the feathers, and comparing it with other capercaillie populations in Europe and Scandinavia, we can identify what we need to do to help the birds and develop an action plan in response. This may involve exploring the reintroduction of birds from abroad to help expand the gene pool.
Read the full research report about how the DNA was extracted from capercaillie feathers and what we learnt.