Nest and nest tree characteristics of Great Spotted Woodpeckers Dendrocopos major - a fifteen year survey in Sapporo, Hokkaido.
Nesting Great Spotted Woodpeckers Dendrocopos major were observed for 15 years (1995-2009) in deciduous broad-leaved forests and conifer plantations of Sapporo, Hokkaido, northern Japan. The woodpeckers excavated nest holes in deciduous broad-leaved trees of 23 species and in coniferous trees of 2 species. The most excavated trees were Japanese White Birch Betula platyphylla (23.9% of 301 nesting cases) and Sargent's Cherry Prunus sargentii (20.6%). Nests were most frequently excavated in dead trees (59.5% of nesting cases), but were also made in live trees (36.9%) and dead parts of live trees (3.7%). Nest cavities were in trees without (51.8%) and with (48.2%) stem broken off (stumps). The dimensions of nest trees and nest cavities fell mostly within in the ranges of dimensions in previous studies. The heights of nests in stumps did not differ from those in trees without stems broken off. Nests in planted Japanese Larches Larix leptolepis were significantly lower than those in deciduous broad-leaved trees. The mean orientation of nest entrances was close to the north, although the mean vector length, a measure of concentration, was short (0.18). No change was detected in nest and nest tree characteristics before and after nest hole destruction presumed to have been caused by introduced Northern Raccoons Procyon lotor. On the other hand, the diameters at both breast and nest heights were significantly increased after the damage due to Typhoon T0418 (Songda) in 2004.