front, and the other one pointing backward. 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. How could toes grow from legs
without any feet between? They never do! There has to be a foot in
every animal between the toes and the legs. Now what do you call the end
of your foot which is opposite the end on which the toes grow?"

[Illustration: FIG. 1. Ordinary foot of perching birds; 2. Foot of
Nighthawk, with a comb on claw of middle toe; 3. Climbing foot of
Woodpecker, with two hind toes; 4. Grasping foot of Osprey, for holding
prey.]

[Illustration: FIG. 5. Scratching foot of Ruffed Grouse; 6. Wading foot
of Golden Plover, with only three toes; 7. Wading foot of Snipe, with
short hind toe; 8. Wading foot of Green Heron, with long hind toe; 9.