Aythya americana vs redhead

Aythya americana and redhead both are nouns.

Word	Noun	Adjective	Verb	Adverb
Aythya americana	Yes	No	No	No
redhead	Yes	No	No	No

As nouns, Aythya americana and redhead are synonyms defined as:

Aythya americana and redhead: North American diving duck with a grey-and-black body and reddish-brown head

Aythya americana (noun)	redhead (noun)
North American diving duck with a grey-and-black body and reddish-brown head	black-and-white North American woodpecker having a red head and neck
	North American diving duck with a grey-and-black body and reddish-brown head
	someone who has red hair