sawbill vs merganser

sawbill and merganser both are nouns.

Word	Noun	Adjective	Verb	Adverb
sawbill	Yes	No	No	No
merganser	Yes	No	No	No

As nouns, sawbill and merganser are synonyms defined as:

sawbill and merganser: large crested fish-eating diving duck having a slender hooked bill with serrated edges

Other synonyms of sawbill include fish duck, sheldrake.

sawbill (noun)	merganser (noun)
large crested fish-eating diving duck having a slender hooked bill with serrated edges	large crested fish-eating diving duck having a slender hooked bill with serrated edges