blackcap vs Old World warbler

blackcap and Old World warbler both are nouns.

Word	Noun	Adjective	Verb	Adverb
blackcap	Yes	No	No	No
Old World warbler	Yes	No	No	No

As nouns, Old World warbler is a hypernym of blackcap; that is, Old World warbler is a word with a broader meaning than blackcap:

Other hypernyms of blackcap include true warbler.

blackcap (noun)	Old World warbler (noun)
small brownish-grey warbler with a black crown	small active brownish or greyish Old World birds
chickadee having a dark crown
small black-headed European gull
raspberry native to eastern North America having black thimble-shaped fruit