black-necked grebe vs eared grebe

black-necked grebe and eared grebe both are nouns.

Word	Noun	Adjective	Verb	Adverb
black-necked grebe	Yes	No	No	No
eared grebe	Yes	No	No	No

As nouns, black-necked grebe and eared grebe are synonyms defined as:

black-necked grebe and eared grebe: small grebe with yellow ear tufts and a black neck; found in Eurasia and southern Africa as well as western United States

Other synonyms of black-necked grebe include Podiceps nigricollis.

black-necked grebe (noun)	eared grebe (noun)
small grebe with yellow ear tufts and a black neck; found in Eurasia and southern Africa as well as western United States	small grebe with yellow ear tufts and a black neck; found in Eurasia and southern Africa as well as western United States