moa vs ratite bird

moa and ratite bird both are nouns.

Word	Noun	Adjective	Verb	Adverb
moa	Yes	No	No	No
ratite bird	Yes	No	No	No

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

moa: extinct flightless bird of New Zealand
ratite bird: flightless birds having flat breastbones lacking a keel for attachment of flight muscles: ostriches, cassowaries, emus, moas, rheas, kiwis, elephant birds

Other hypernyms of moa include flightless bird, ratite.

moa (noun)	ratite bird (noun)
extinct flightless bird of New Zealand	flightless birds having flat breastbones lacking a keel for attachment of flight muscles: ostriches, cassowaries, emus, moas, rheas, kiwis, elephant birds