Nature clicks #125 - Dusky Grouse (?)

Dusky Grouse  

It is not easy to identify a grouse and I'm not 100 percent sure if I'm correct in this matter. According to iBird PRO, a terrific app that I use for bird identification, the Dusky Grouse and the Sooty Grouse were considered to be the same species, called the Blue Grouse. In 2006 the American Ornithologist's Union split them based on DNA evidence. Beside iBird PRO I use several books to identify my bird encounters. However, this time I'm not really sure and if you have a different opinion I like to hear from you and would appreciate any professional advice.

This photo took a lot of efforts to get the shot. This female grouse was not very shy but wandered constantly around between rocks and trees laying on the ground. The light was low and I had to dial in ISO400 in order to get a shutter speed of 1/60s. The D300s was handhold and I tried to stabilize the lens by leaning against a tree. I got several sharp images but my choice to publish this photo was based on the background. The Dusky Grouse rested briefly on a rock in front of some other boulders and no twig or dead branch disturbed the scene...