Nest-site selection by crossbills Loxia spp. in ancient native pinewoods at Abernethy Forest, Strathspey, Highland

Capsule Birds preferred stands with a particular density of trees, perhaps to avoid predation, and they selected aspects sheltered from prevailing winds. Aim To describe the nesting habitat and tree selection by crossbills in a restricted pinewood habitat in Scotland. Methods Scots Pines used by nesting crossbills were described and compared with randomly selected pines. Nest aspect was related to wind strength and direction. Results The crossbills selected trees at a density of 50–60 trees/ha. Such stands may be sufficiently dense to provide cover, yet occur at a low enough density to minimize being visited by potential arboreal predators, such as Red Squirrels and Pine Martens. Crossbills tended to nest on lateral branches on the northeast side of crowns. Tree crown development was not asymmetric, so the birds may choose the northeast side to shelter from the prevailing southerly to westerly winds. Conclusion Stands of pines at a low density need to be maintained for the benefit of crossbills.