Matthew Geary

and 2 more

Capercaillie in Scotland have declined in number and contracted in range since the 1970s, most remaining in Strathspey on the northwest flank of the Cairngorm mountains. Strathspey, however, is popular for recreation and suffers anthropogenic disturbance from visitors and their use of new forest tracks and remote, off-track areas. Disturbance reduces the area of forest available to Capercaillie. Refuge areas wherein the creation of new tracks is not allowed, and in which recreation is not encouraged, are a management option that might mitigate such effects. We simulate this possibility for the area covered by Forest and Land Scotland’s Strathspey Land Management Plan. Spatially explicit, stage-based matrix models assessed the potential of protecting this population with refuges under ‘optimistic’, ‘central’ and ‘pessimistic’ scenarios based on observed demographic data. Fifteen potential refuges comprised less-disturbed areas of forest still used by Capercaillie. We simulated population growth using combinations of 1, 3, 5, 7, 10, 12 and the full complement of 15 refuge areas. An increasing Capercaillie population could be sustained by a network of refuges, but refuges could not arrest a wider population decline due to causes other than disturbance. This suggests that refuges could play a role in mitigating the increasingly damaging effects of disturbance on Capercaillie in the Strathspey LMP but that the birds’ long-term prospects will depend upon improving their performance more widely.

Robert Moss

and 3 more

Wild vertebrates usually avoid ground disturbed by humans but consequences for their distribution and density are uncertain. The local distribution of capercaillie shifted after an increase in disturbance along woodland tracks adjacent to an expanding Scottish village. We surveyed the birds’ droppings before and after the building of 30 new houses, and model the probability of finding droppings (Pf) in relation to period plus two disturbance gradients – distance to a much disturbed ‘entry zone’ by the village (dE) and ‘distance to nearest track’ (dT). Estimates of Pf are benchmarked to average Pf (Pfav) – a notional scenario in which the birds’ distribution is unaffected by tracks. Change between periods occurred mainly on a strip of ground centred on tracks and averaging 80 m wide, where Pf fell from about 0.5 Pfav before the development to 0.2 Pfav after it. By contrast, Pf on ground 120–260 m from tracks, under a third of the 273 ha main study area, remained at about 3 Pfav throughout the study – indicating a net influx of capercaillie displaced from ground beside tracks in both periods. No capercaillie droppings were found in the entry zone. Beyond this zone, throughout the study, Pf increased as tracks sparsened until dE approached 400 m – whereupon track density and Pf steadied together. Beyond 400 m, Pf remained depressed on ground near tracks (dT ⪅ 100 m). New desire paths after the development caused the proportion of ground where dT < 100 m to increase slightly, from 56% to 60%. Birds on roughly half of a 50 ha refuge should be undisturbed by direct effects of track-based activities – but, if increases in density caused by displaced birds are also deemed disturbance, a refuge would need to be over 3 km2 to keep half of it undisturbed.