grass finch vs weaver finch

grass finch and weaver finch both are nouns.

Word	Noun	Adjective	Verb	Adverb
grass finch	Yes	No	No	No
weaver finch	Yes	No	No	No

As nouns, weaver finch is a hypernym of grass finch; that is, weaver finch is a word with a broader meaning than grass finch:

grass finch: usually brightly-colored Australian weaverbirds; often kept as cage birds
weaver finch: finch-like African and Asian colonial birds noted for their elaborately woven nests

Other hypernyms of grass finch include weaver, weaverbird.

grass finch (noun)	weaver finch (noun)
usually brightly-colored Australian weaverbirds; often kept as cage birds	finch-like African and Asian colonial birds noted for their elaborately woven nests
common North American finch noted for its evening song