Q: Why don’t birds fall off their...

Q: Why don’t birds fall off their perch when they are sleeping?

A: According to ornithologist David Rimlinger, curator of birds at the San Diego Zoo, tendons in a bird’s feet, called flexor tendons, respond to pressure from the perch and automatically lock the feet around it when the bird lands. The feet grip until the bird consciously releases the grasp to fly away. Rimlinger speculates that evolution favored this technique, at least in part because birds do not see well at night and are thus much safer when they remain on a perch.