bird vs protoavis

bird and protoavis both are nouns.

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

bird: warm-blooded egg-laying vertebrates characterized by feathers and forelimbs modified as wings
protoavis: most primitive avian type known; extinct bird of the Triassic having bird-like jaw and hollow limbs and breastbone with dinosaur-like tail and hind limbs

Other hyponyms of bird include dickey-bird, dickeybird, dicky-bird, dickybird, cock, hen, nester, night bird, bird of passage, Archaeopteryx lithographica, archaeopteryx, archeopteryx, Sinornis, Ibero-mesornis, archaeornis, ratite, ratite bird, flightless bird, carinate, carinate bird, flying bird, passeriform bird, passerine, nonpasserine bird, raptor, raptorial bird, bird of prey, gallinacean, gallinaceous bird, parrot, cuculiform bird, coraciiform bird, apodiform bird, caprimulgiform bird, piciform bird, trogon, aquatic bird, twitterer.

bird (noun)	protoavis (noun)
warm-blooded egg-laying vertebrates characterized by feathers and forelimbs modified as wings	most primitive avian type known; extinct bird of the Triassic having bird-like jaw and hollow limbs and breastbone with dinosaur-like tail and hind limbs
the flesh of a bird or fowl (wild or domestic) used as food
informal terms for a (young) woman
a cry or noise made to express displeasure or contempt
badminton equipment consisting of a ball of cork or rubber with a crown of feathers

bird (verb)	protoavis (verb)
watch and study birds in their natural habitat