Seasonal changes of the Hazel Grouse Tetrastes bonasia habitat requirements in managed mountain forests (Western Carpathians)

We studied the differences between spring and winter sites of Hazel Grouse Tetrastes bonasia in a managed, temperate forest in the Beskid Mountains (Western Carpathians, Poland). The study of seasonal requirements of this species in this type of habitat was innovatory. Spring territories must provide birds with appropriate conditions for breeding and winter ones must give good habitat for wintering. The environmental variables of spring and winter sites were collected in three layers in a 100 m radius from the place of recording of the Hazel Grouse: canopy, understory and undergrowth. According to our study, the proportion of deciduous trees was greater in spring territories in comparison to winter territories in all studied layers. Conversely, greater species richness in the undergrowth and understory in spring sites of Hazel Grouse was found in comparison to winter sites. Moreover, a greater proportion of birch, poplar, willow, wild cherry and bird cherry were found in the spring sites of Hazel Grouse in comparison to winter sites. Generalized Linear Model models showed that the occurrence of overgrown clearings, clearfellings with deadwood and higher richness of grass and herbs and their cover in the forest were important habitat factors for Hazel Grouse in both spring and winter sites. Sites of Hazel Grouse were strongly affected by the proportions of beech, sycamore, fir, spruce and larch in the canopy layer in both seasons. Moreover, a greater proportion of tree species producing nuts, drupes or winged seeds was important in both spring and winter sites. Bush cover was important for winter sites of the Hazel Grouse. Food resources, mainly in winter sites are important factors for habitat selection. Summarizing, we found habitat differences between spring territory and winter sites of Hazel Grouse. In both seasons, higher habitat heterogeneity was an important factor for occurrence of this species.