lake duck vs broadbill

lake duck and broadbill both are nouns.

Word	Noun	Adjective	Verb	Adverb
lake duck	Yes	No	No	No
broadbill	Yes	No	No	No

As nouns, broadbill is a hypernym of lake duck; that is, broadbill is a word with a broader meaning than lake duck:

Other hypernyms of lake duck include bluebill, scaup, scaup duck.

lake duck (noun)	broadbill (noun)
common scaup of North America; males have purplish heads	small birds of the Old World tropics having bright plumage and short wide bills
	freshwater duck of the Northern Hemisphere having a broad flat bill
	diving ducks of North America having a bluish-grey bill
	tropical American heron related to night herons