Regulus regulus vs goldcrest

Regulus regulus and goldcrest both are nouns.

Word	Noun	Adjective	Verb	Adverb
Regulus regulus	Yes	No	No	No
goldcrest	Yes	No	No	No

As nouns, Regulus regulus and goldcrest are synonyms defined as:

Regulus regulus and goldcrest: European kinglet with a black-bordered yellow crown patch

Other synonyms of Regulus regulus include golden-crested kinglet.

Regulus regulus (noun)	goldcrest (noun)
European kinglet with a black-bordered yellow crown patch	European kinglet with a black-bordered yellow crown patch