[Tweeters] help with Grouse ID

[Gene Beall via Tweeters]

I would really appreciate some help confirming the ID of a grouse I 
photographed this afternoon in Kittitas County on the north slope of 
Lookout Mountain.  I think it's a Sooty Grouse but I'm not certain.  The 
Merlin app suggested both Sooty and Dusky.  The range maps in eBird for 
these two species would suggest it's a Sooty. The photos in eBird 
weren't strongly suggestive of one or the other for me.  Here's a link 
to a half dozen photos: 
https://www.flickr.com/photos/gene-s_photos/albums/72177720320126475/

If you have comments on the ID I'd also appreciate learning what the 
distinguishing features are.

Thank you for your assistance!

Gene Beall
Sammamish, WA
gene.beall at gmail.com