That is what makes its foot as good as a hand to hold on with when it perches on slender twigs.
Almost all birds have their toes fixed that way.

Some, that do not perch, have no hind toe; and birds that swim have broad webs stretched between their front toes, like Ducks.

All the different kinds of feet birds have are fitted for the ways they move about on the ground, or water, or among the branches of trees and bushes, just as all their shapes of beaks are fitted for the kind of food they eat and the way they pick it up.

Here are two pictures that will show you several different kinds of feet.

Now you must answer the next question, Nat; what do toes grow on ?" "Feet!" said Nat promptly, then adding: "But this Sparrow hasn't any feet except its toes; they grow on its legs, because the rest of the horny part stands up--I've noticed that in Canaries." "But all this horny part is the foot, not the leg," answered the Doctor, "though it does stand up, as you say.