zygodactyl foot vs bird's foot

zygodactyl foot and bird's foot both are nouns.

Word	Noun	Adjective	Verb	Adverb
zygodactyl foot	Yes	No	No	No
bird's foot	Yes	No	No	No

As nouns, bird's foot is a hypernym of zygodactyl foot; that is, bird's foot is a word with a broader meaning than zygodactyl foot:

zygodactyl foot: a bird's foot having the first and fourth toes of each foot directed backward and the second and third forward
bird's foot: the foot of a bird

zygodactyl foot (noun)	bird's foot (noun)
a bird's foot having the first and fourth toes of each foot directed backward and the second and third forward	the foot of a bird