catbird vs grey catbird

catbird and grey catbird both are nouns.

Word	Noun	Adjective	Verb	Adverb
catbird	Yes	No	No	No
grey catbird	Yes	No	No	No

As nouns, catbird and grey catbird are synonyms defined as:

catbird and grey catbird: North American songbird whose call resembles a cat's mewing

Other synonyms of catbird include Dumetella carolinensis, gray catbird.

catbird (noun)	grey catbird (noun)
North American songbird whose call resembles a cat's mewing	North American songbird whose call resembles a cat's mewing
any of various birds of the Australian region whose males build ornamented structures resembling bowers in order to attract females