grey kingbird vs gray kingbird

grey kingbird and gray kingbird both are nouns.

Word	Noun	Adjective	Verb	Adverb
grey kingbird	Yes	No	No	No
gray kingbird	Yes	No	No	No

As nouns, grey kingbird and gray kingbird are synonyms defined as:

grey kingbird and gray kingbird: a kingbird that breeds in the southeastern United States and winters in tropical America; similar to but larger than the eastern kingbird

Other synonyms of grey kingbird include petchary, Tyrannus domenicensis domenicensis.

grey kingbird (noun)	gray kingbird (noun)
a kingbird that breeds in the southeastern United States and winters in tropical America; similar to but larger than the eastern kingbird	a kingbird that breeds in the southeastern United States and winters in tropical America; similar to but larger than the eastern kingbird