Aythya marila vs bluebill

Aythya marila and bluebill both are nouns.

Word	Noun	Adjective	Verb	Adverb
Aythya marila	Yes	No	No	No
bluebill	Yes	No	No	No

As nouns, bluebill is a hypernym of Aythya marila; that is, bluebill is a word with a broader meaning than Aythya marila:

Aythya marila: large scaup of North America having a greenish iridescence on the head of the male
bluebill: diving ducks of North America having a bluish-grey bill

Other hypernyms of Aythya marila include broadbill, scaup, scaup duck.

Aythya marila (noun)	bluebill (noun)
large scaup of North America having a greenish iridescence on the head of the male	diving ducks of North America having a bluish-grey bill