sedge warbler vs true warbler

sedge warbler and true warbler both are nouns.

Word	Noun	Adjective	Verb	Adverb
sedge warbler	Yes	No	No	No
true warbler	Yes	No	No	No

As nouns, true warbler is a hypernym of sedge warbler; that is, true warbler is a word with a broader meaning than sedge warbler:

sedge warbler: small European warbler that breeds among reeds and wedges and winters in Africa
true warbler: small active brownish or greyish Old World birds

Other hypernyms of sedge warbler include Old World warbler.

sedge warbler (noun)	true warbler (noun)
small European warbler that breeds among reeds and wedges and winters in Africa	small active brownish or greyish Old World birds