Why don't birds fall off branches? Birds don't fall because they are locked into place when they land on branches.
Long tendons run all the way down the inside of a bird's legs to its toes.
A bird bends its legs when it settles on a branch. Bending pulls the tendons. The tendons pull on the toes, making them curl around the branch.
As long as the bird is perched on the branch, its legs are bent, and as long as its legs are bent, its toes are locked in place, so it will not fall, even if it's asleep.
What causes tides? Tide refers to the daily rise and fall of sea level in oceans and other large bodies of water. These changes are caused mainly by the gravitational attraction of the moon.
If the moon attracted every point on the Earth with equal force, there would be no tides. But according to Newton's law of gravitation, the gravitational force decreases as the distance increases.