What I have heard, at least to me, doesn't sound like grouse either, I mentioned it because I'm fully aware that the immediate BF assumption leads nowhere very quickly and to be honest, I have no idea what was making those sounds. All I know is that under the circumstances that I heard these sounds
BFF makes me think this was something other than a grouse but then again, I didn't see anything so I'm once again left to the same conclusions everyone else is...who knows?
When you heard whatever it was appear to be getting closer, I'll bet the adrenalin was kicking in on high! I really wish that I wasn't alone during my experience, I'm pretty sure I would have been able to sit down and wait it out as well but with all that was going on, my only concern was getting the hell out of there!
Cheers