ibis vs wading bird

ibis and wading bird both are nouns.

Word	Noun	Adjective	Verb	Adverb
ibis	Yes	No	No	No
wading bird	Yes	No	No	No

As nouns, wading bird is a hypernym of ibis; that is, wading bird is a word with a broader meaning than ibis:

ibis: wading birds of warm regions having long slender down-curved bills
wading bird: any of many long-legged birds that wade in water in search of food

Other hypernyms of ibis include wader.

ibis (noun)	wading bird (noun)
wading birds of warm regions having long slender down-curved bills	any of many long-legged birds that wade in water in search of food