lesser scaup duck vs lake duck

lesser scaup duck and lake duck both are nouns.

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

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

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

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

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