corncrake vs Crex crex

corncrake and Crex crex both are nouns.

Word	Noun	Adjective	Verb	Adverb
corncrake	Yes	No	No	No
Crex crex	Yes	No	No	No

As nouns, corncrake and Crex crex are synonyms defined as:

corncrake and Crex crex: common Eurasian rail that frequents grain fields

Other synonyms of corncrake include land rail.

corncrake (noun)	Crex crex (noun)
common Eurasian rail that frequents grain fields	common Eurasian rail that frequents grain fields