The consumption of mountain pine seeds by small vertebrates before their dispersal in eastern Pyrénées

The consumption of Mountainpine seeds (Pinus uncinata) by small vertebeates before their dispersal was studied in a forest of the Eastern Pyrénées (Osséja, 42° 23' N, 2° E). Seed production was estimated, and predation signs (expl oited cones, seed wings) convertible into numbers of seeds eaten by each identified consumer, were counted. The field work was carried out between Autumn 1981 and Autumn 1982, in five areas with d ifferent tree densities. The Common Crossbill (Loxia curvirostra), which was responsible for the largest consumption (15 to 31 % of the 1981 production) and is almost exclusively granivorous, adapted its movements to the spatial and temporal variability of the seed supply, and had a major impact on seed production in the forest clearings. The Spotted woodpecker (Dendrocopos major) and the Red squirrel (Sciurus vulgaris), which are exclusively granivorous only during the snowy season, were more sedentary and tended to occupy and exploit fairly thick or heavy-leaved timbers. Their respective i mpact only affected 1 t o 4 % of the production. The Coal tit (Parus ater) and the Crested tit (Parus cristalus) had a negligible impact. The total rate of predation on the 1981 production ranged from 20 % in the densest areas to 32 % in the clearings. Seed resources were utilized most equitably in winter time in the habitats most favoured by the Spotted woodpecker and the Squirre