These are large grouse that inhabit highland regions of North America and Eurasia. The sooty grouse is found in the Pacific Coast Ranges and Sierra Nevada, and the dusky grouse in the Rocky Mountains. These two taxa were originally regarded as separate species, but were considered conspecific for much of the twentieth century. However, in 2006 the American Ornithologists' Union re-split them, following the DNA-based work of Barrowclough et al. (2004). whose results supported the earlier work of Brooks (1929) who regarded the two taxa as separate species based on morphology, behavior and vocalizations. The precise ranges of the two species are well-defined in the south, separated by extensive areas of unsuitable forest-free habitat, but somewhat uncertain in the north of the range of the genus where there is no separation; Barrowclough et al. 's study did not include these northern populations.