The importance of habitat diversity and plant species richness for hazel grouse occurrence in the mixed mountain forests of the Western Carpathians

Abstract

Hazel grouse habitat requirements are relatively well known in coniferous forests, and less known in mixed or deciduous forests. We studied habitat differences between sites occupied by hazel grouse Tetrastes bonasia and control plots in mixed mountain forests of the Western Carpathians in 2009 and 2010. Hazel grouse presence at sites was determined in April and May. The habitat variables (n = 21) and the proportion of tree and shrub species (n = 22) were collected both in sites of hazel grouse presence and control plots within a radius of 100 m. Greater numbers of tree species and greater proportions of deciduous trees (mainly birch Betula sp.) were found in sites where hazel grouse was present. Lower canopy cover was an important variable for hazel grouse occurrence, and sites with hazel grouse had a greater proportion of young trees (< 40 years). Sites were also characterized by a higher proportion of overgrown glades and dead woods in comparison with control plots. Sites occupied by hazel grouse were characterized by a greater number of tree species in the undergrowth (minimum of five species) in comparison with control plots. GLM models revealed that the most important environmental factors for hazel grouse occurrence in mixed mountain forests were open habitats (overgrown glades), good hiding opportunities (fallen trees and dead woods) and good conditions for foraging (trees cover in undergrowth). Poplar (Populus sp.) and willow (Salix sp.) were the most important tree species for hazel grouse occurrence. The presence of habitat structures and the vegetations richness provides good shelter or food for the hazel grouse. Extensive forest management should be proposed to increase the number of hazel grouse. Large areas covered by herbs and light-seeded tree species of low economical value for forestry are recommended to support hazel grouse population.