Factors affecting anvils utilization by great spotted woodpecker Dendrocopos major

Three factors which are assumed to influence the frequency of anvil utilization by Great Spotted Woodpecker were studied. They were: (1) microhabitat characteristic, (2) seasonal changes in the cones' availability and (3) size of hammered cones. Anvil location and number of pines Pinus silvestris in 10 m radius (as food resource availability) were described. Hammered cones were collected, counted and measured (length, width). Number of pines didn't influence the intensity of anvil utilization. Particular groups of anvils (main, secondary and ancillary) were exploited throughout the winter in similar way, although in main and secondary anvils there was decrease in the average length of the hammered cones. In particular anvils cones in different sizes were hammered, and intensity of utilization was correlated with the average length and range of length of opened cones. We argue that ancillary anvils are used for opening the cones of specific shape.