genus Silvia vs bird genus

genus Silvia and bird genus both are nouns.

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

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

genus Silvia (noun)	bird genus (noun)
type genus of the Sylviidae: warblers	a genus of birds