blue tit vs titmouse

blue tit and titmouse both are nouns.

Word	Noun	Adjective	Verb	Adverb
blue tit	Yes	No	No	No
titmouse	Yes	No	No	No

As nouns, titmouse is a hypernym of blue tit; that is, titmouse is a word with a broader meaning than blue tit:

blue tit: widely distributed European titmouse with bright cobalt blue wings and tail and crown of the head
titmouse: small insectivorous birds

Other hypernyms of blue tit include tit.

blue tit (noun)	titmouse (noun)
widely distributed European titmouse with bright cobalt blue wings and tail and crown of the head	small insectivorous birds