[Illustration: FIG. 1. Insect-eating bill of Robin; 2. Seed-crushing bill of a Sparrow; 3. Snapping bill of Whip-poor-will; 4. Needle bill of Hummingbird; 5. Chiselling bill of Woodpecker; 6. Climbing bill of Paroquet; 7. Tearing bill of Falcon; 8. Grooved drinking bill of Dove; 9. Gleaning bill of Ruffed Grouse; 10. Wedge bill of Plover; 11. Straight probing bill of Snipe.] [Illustration: FIG 12: Curved probing bill of Curlew; 13. Spearing bill of Green Heron; 14. Strainer bill of Duck; 15. Hooked bill of Gull; 16. Ornamental bill of male Puffin in breeding season.] "I know!" exclaimed Dodo, "toe-nails! Only I think they need cutting!" "Of course they are toe-nails," said the Doctor. "Don't nails grow on the ends of toes? All kinds of claws, on the ends of birds' and other animals' toes, are the same as nails. Some are long, sharp, and curved, like a cat's or a Sparrow's, and some are flat and blunt, like ours. I could show you some birds with claws that look just like our finger-nails. Toes, too, are pretty much the same; only this Sparrow, like most other birds, has but four, with three of them in a line in 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. Swimming foot of Coot, with lobed toes; 10. Swimming foot of Canada Goose, with three toes webbed; 11. Swimming foot of Cormorant, with all four toes webbed.]