For the plains grouse (sharptails/prairie chickens) you need something with alot of kick. Especially with them being so wary. I like 4-6's 3in shells 1 7/8oz. You walk a long ways per shot, so they need to fall or give yourself the best chance.
The forest grouse you can use just low brass dove loads, but I personally will only use #6's or #71/2 high brass from now on.
Went last year and hunted two states, both had blue and ruffed, one state I had some nice high brass 6's and dropping them like flies. I then go to WA and used up all the other shells so had to buy cheap dove loads, was just not very effective and will never make that mistake twice.
Chukars........well..........., I will never forget my first venture after wild Chukars in Nevada
Just need something with some punch, from depending on how your hunting them you should be getting not too far of shots. Just some high velocity 2 3/4 #6s would be my call