foot vs bird's foot

foot and bird's foot both are nouns.

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

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

Other hyponyms of foot include fossorial foot, hoof, webfoot, trotter, forefoot, hindfoot, paw.

foot (noun)	bird's foot (noun)
travel by walking	the foot of a bird
any of various organs of locomotion or attachment in invertebrates
the pedal extremity of vertebrates other than human beings
lowest support of a structure
a support resembling a pedal extremity
the part of the leg of a human being below the ankle joint
(prosody) a group of 2 or 3 syllables forming the basic unit of poetic rhythm
an army unit consisting of soldiers who fight on foot
the lower part of anything
a member of a surveillance team who works on foot or rides as a passenger
a linear unit of length equal to 12 inches or a third of a yard