genus Pterocnemia vs bird genus

genus Pterocnemia and bird genus both are nouns.

Word	Noun	Adjective	Verb	Adverb
genus Pterocnemia	Yes	No	No	No
bird genus	Yes	No	No	No

As nouns, bird genus is a hypernym of genus Pterocnemia; that is, bird genus is a word with a broader meaning than genus Pterocnemia:

genus Pterocnemia (noun)	bird genus (noun)
a genus of birds of the family Rheidae	a genus of birds