webbed foot vs bird's foot

webbed foot and bird's foot both are nouns.

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

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

webbed foot (noun)	bird's foot (noun)
a bird's foot with folds of skin between the toes	the foot of a bird