game bird vs grouse

game bird and grouse both are nouns.

Word	Noun	Adjective	Verb	Adverb
game bird	Yes	No	No	No
grouse	Yes	No	Yes	No

As nouns, grouse is a hyponym of game bird; that is, grouse is a word with a more specific, narrower meaning than game bird:

Other hyponyms of game bird include phasianid, partridge, tinamou.

game bird (noun)	grouse (noun)
any bird (as grouse or pheasant) that is hunted for sport	popular game bird having a plump body and feathered legs and feet
	flesh of any of various grouse of the family Tetraonidae; usually roasted; flesh too dry to broil

game bird (verb)	grouse (verb)
	complain
	hunt grouse