lake duck vs lesser scaup duck

lake duck and lesser scaup duck both are nouns.

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

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

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

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

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