American redstart vs redstart

American redstart and redstart both are nouns.

Word	Noun	Adjective	Verb	Adverb
American redstart	Yes	No	No	No
redstart	Yes	No	No	No

As nouns, American redstart and redstart are synonyms defined as:

American redstart and redstart: flycatching warbler of eastern North America the male having bright orange on sides and wings and tail

Other synonyms of American redstart include Setophaga ruticilla.

American redstart (noun)	redstart (noun)
flycatching warbler of eastern North America the male having bright orange on sides and wings and tail	European songbird with a reddish breast and tail; related to Old World robins
	flycatching warbler of eastern North America the male having bright orange on sides and wings and tail