[tehjoker]

If a bird gets overweight and/or doesn't have enough different surfaces to grip, it will develop pressure sores on its feet just to add some nuance.

[Swizec]

Our parrot came with a crooked toe (probably dislocated when he was a baby) and he has a permanent pressure sore in his foot, to add even more nuance. It’s the foot he preferences when standing or sleeping so I don’t think it’s a big problem.