water bird vs screamer

water bird and screamer both are nouns.

Word	Noun	Adjective	Verb	Adverb
water bird	Yes	No	No	No
screamer	Yes	No	No	No

As nouns, screamer is a hyponym of water bird; that is, screamer is a word with a more specific, narrower meaning than water bird:

water bird: freshwater aquatic bird
screamer: gooselike aquatic bird of South America having a harsh trumpeting call

Other hyponyms of water bird include anseriform bird.

water bird (noun)	screamer (noun)
freshwater aquatic bird	a very hard hit ball
	gooselike aquatic bird of South America having a harsh trumpeting call
	a sensational newspaper headline
	someone who communicates vocally in a very loud voice