The sleeping birds do not fall because they are ‘locked’ in the place or branches. Two thin tendons, called ‘flexor tendons’, extend from the leg muscles down the back of the tarsus bone and attach to the toes. When a bird lands on a perch, these tendons tighten and so the toes lock around the perch. This involuntary reflex keeps a sleeping bird from falling off a perch as long as it keeps sitting on it.
Why do sleeping birds not fall from trees?
