lesser scaup vs lake duck

lesser scaup and lake duck both are nouns.

Word	Noun	Adjective	Verb	Adverb
lesser scaup	Yes	No	No	No
lake duck	Yes	No	No	No

As nouns, lesser scaup and lake duck are synonyms defined as:

lesser scaup and lake duck: common scaup of North America; males have purplish heads

Other synonyms of lesser scaup include Aythya affinis, lesser scaup duck.

lesser scaup (noun)	lake duck (noun)
common scaup of North America; males have purplish heads	common scaup of North America; males have purplish heads