Blue grouse Dendragapus obscurus are now considered to be two species: dusky grouse (Dendragapus obscurus) and sooty grouse (Dendragapus fuliginosus)

The American Ornithologists' Union (AOU) has split the blue grouse Dendragapus obscrurus into two separate species: dusky grouse D. obscurus and sooty grouse D. fuliginosus (AOU 2006). This split is actually a reversion to the previous designation during the early 1900's when dusky and sooty grouse were considered distinct. The current reclassification was justified by the AOU on the basis of mitochondrial DNA research by Barrowclough et al. (2004), but also on early research by Brooks (1929) where he described differences in the tail, cervical apteria, and volume of the hooting display.