elephant bird vs ratite

elephant bird and ratite both are nouns.

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

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

elephant bird: huge (to 9 ft.) extinct flightless bird of Madagascar
ratite: flightless birds having flat breastbones lacking a keel for attachment of flight muscles: ostriches, cassowaries, emus, moas, rheas, kiwis, elephant birds

Other hypernyms of elephant bird include flightless bird, ratite bird.

elephant bird (noun)	ratite (noun)
huge (to 9 ft.) extinct flightless bird of Madagascar	flightless birds having flat breastbones lacking a keel for attachment of flight muscles: ostriches, cassowaries, emus, moas, rheas, kiwis, elephant birds