Habitat requirements of Black Grouse.
Black Grouse Tetrao tetrix are found in a wide variety of habitats throughout their range and probably have the broadest habitat requirements of the three Eurasian forest grouse species. Typically, they are regarded as birds of early stage succession forest, either coniferous or birch Betula spp. and forest edge habitats, particularly in boreal zones. Outside the boreal regions, Black Grouse are found in structurally similar habitats comprised of mosaics of moorland or heathland, coniferous plantations, rough grazing fields and meadows (Degn 1973, Ellison 1979, Parr and Watson 1988, Baines 1994). In many of these habitats, their association with woodland is not strong, with preferred tree crown cover 0.3 - 12% (Beichle 1987). Open canopied coniferous woodlands of pine, spruce or larch allow sufficient sunlight to reach the forest floor and create a field layer rich in herbs, bilberry Vaccinium myrtillus and rhododendron Rhododendron ferrugineum attractive to Black Grouse. Closed canopy woods have no such field layer and tend to be avoided.
By having such a wide range of habitat preferences, identifying particular habitat requirements pertinent to all populations across the species' range is difficult. Black Grouse feed selectively according to the nutritive quality, availability and digestibility of the food items. I suggest that there are three potentially limiting dietary stages for Black Grouse; these are a protein and energy rich food source for females in the pre-Iaying period, adequate invertebrates preferred by chicks, and a reliable winter food source.
This review attempts to concentrate on similarities over how these requirements are met by different Black Grouse populations. Current knowledge is discussed under the headings of winter food, spring food, breeding requirements and spatial or landscape ecology. Research recommendations aimed at filling gaps in our understanding of the wider requirements of Black Grouse are suggested.