Habitat selection by Cantabrian capercaillie Tetrao urogallus cantabricus at the edge of the species' distribution

Abstract

We studied the patterns of habitat availability and use by the Cantabrian capercaillie Tetrao urogallus cantabricus, an isolated and endangered population at the southwestern edge of the species distribution. We combined field surveys and GIS analyses to show that this population differs from its conifer-specialist conspecifics in that it inhabits beech Fagus sylvatica and oak Quercus petraea forests, without specialisation as regards the tree species as long as enough forest cover remains. The habitat of Cantabrian capercaillie is highly fragmented, and smaller forest patches have been abandoned during the last few decades; the display areas that remain occupied are now located farther from forest edges. Lower tree density and more widespread distribution of bilberry Vaccinium myrtillus characterised the occupied display grounds. However, even abandoned areas showed tree densities well within the optimum range for capercaillie and bilberry in other populations, a result that should be taken into account before any habitat management action is considered. We found that some non-forested habitats were also used by capercaillie, especially during the autumn and winter. We suggest that the protection of Cantabrian capercaillie should be tightly coupled with an effective, strict protection of the few remaining large forest fragments in the range, and that information about nesting and brood rearing habitat should be obtained. Conditions for understory development should be favoured, preventing overgrazing by ungulates. The natural, non-forested matrix should also be considered in management plans, as a direct source of food and shelter and an important feature determining connectivity among patches.