Capercaillie Disturbance (Scotland)

The Scottish population of Capercaillie (Tetrao urogallus) is thought to have been about 20,000 in the 1970s. This had declined to around 1000 birds in 1998/99. Through conservation measures the population had recovered to c 2000 by the last survey in 2003/04 but breeding success in 2007 and 2008 was very poor and so numbers have probably declined again.

Historically, the bird was a game species but  there was a voluntary ban on shooting it throughout the 1990s. However, the species was eventually afforded legal protection with listing on Annex 1 of the EU Birds Directive and Schedule 1 of the Wildlife and Countryside Act in 2001.

Capercaillie lek site with male
and females.

Capercaillies live in mature conifer forests which have a good understorey of dwarf shrub species. In winter they feed on conifer needles, and during the rest of the year they feed mostly on the ground vegetation, especially blaeberry (Vaccinium myrtillus). Chicks feed on insects for the first few weeks of their lives.

In Scotland, the population is restricted to five core areas: Easter Ross; Moray, Nairn and Speyside; Deeside and Donside; Perthshire; Loch Lomond. The latter two are isolated and very small populations. Easter Ross and Deeside/Donside have small populations (30-35 males at leks monitored in recent years), whilst Speyside, Moray and Nairn remains the stronghold (c 180 males at monitored leks).

Causes of the decline include: climate change; loss and fragmentation of habitat; fence-collision; predation. Disturbance by people, especially during the breeding season, is an increasing threat.

Woodlands are used increasingly by people for recreation and housing. It is thought that disturbance by people, especially those walking dogs, reduces the space available to capercaillies, but the evidence is mostly anecdotal. It is clear that research is needed to understand just what activities disturb capercaillies sufficiently to affect their distribution and population dynamics, and what activities they can tolerate without being disturbed.

In the absence of any useful initiative from relevant organisations, Robert Moss personally instigated research at Anagach Wood in 2006, with the aim of seeing whether the distribution of capercaillie droppings could be used to measure capercaillie distribution in relation to putative sources of disturbance such as tracks and forest entrances. His draft report shows clearly that this simple approach can provide useful information on eg how far the disturbance associated with a track extends and the role of refuge areas (bogs in the case of Anagach). Therefore the study has been extended to include woods at the Boat of Garten and Glenmore and Ballater.

There are two reasons for repeating similar studies in a number of different woods. Firstly, a number of case-histories will make it possible to produce generalisations which will be broadly applicable. Secondly, the results from each wood should be useful in informing management at that wood.

Robert Moss initiated this work at his own expense, with assistance in kind from well-disposed friends and from the RSPB and FCS and SNH. Natural Research’s involvement began in 2008 with input from Fiona Leckie, Amanda Biggins and David Mcleod.  As the study of each wood is completed, a draft report is written so that woodland managers can use the results immediately.

Please click on the following link to view PDF version of a published paper from this project

Photo: C. Knight

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