gray kingbird vs grey kingbird

gray kingbird and grey kingbird both are nouns.

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

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

gray kingbird and grey 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 gray kingbird include petchary, Tyrannus domenicensis domenicensis.

gray kingbird (noun)	grey 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