Unless in flight, birds are their feet 24/7. Actually the bird cage grate is best surface for a parrot's foot. Water birds like seagulls have web or flat feet which is why you'll see seagulls on the top of street lamps not on phone wires. Birds like parrots or say pigeons need to wrap they feet "around" branches perches or cage grates (or phone lines) so as to get a beter grip.

Birds have very few nerves in their feet enabling the to stand on them except when they are in flight. A tendon on the side of a bird leg locks a birds foot around a perch enabling them to sleep standing up. Because of the lack of nerves in their feet, they feel no pain.