"But it is best for Bird People," replied the Doctor, "that the mother bird, who has to keep house and tend to the little ones, should not be too conspicuous. She is best protected from enemies when her colors are plain, and especially when they match the foliage in which she sits on her nest. If her mate has only himself to look out for, it does not so much matter how bright his plumage may be. The colors of some birds are so exactly like their surroundings, that you might look long before you could find the sober, quiet female, whose mate is flashing his gay plumage and singing his finest song, perhaps for the very purpose of attracting your attention away from his home. 'Protective coloration,'

is what the Wise Men call it."

"What makes all the different colors of birds, Doctor?" asked Rap.

"That is a hard question to answer. It is natural for birds to have particular colors, just as some people have black eyes and hair, while others have blue eyes and yellow hair. But I can tell you one thing about that. Look at this Sparrow. All the colors it shows are _in_ the feathers, whose various markings are due to certain substances called 'pigments,' which filter into the feathers, and there set in various patterns. The feathers are painted inside by Nature, and the colors show through. You see none of these colors are shiny like polished metal. But I could show you some birds whose plumage glitters with all the hues of the rainbow. That glittering is called 'iridescence.' It does not depend upon any pigment in the substance of the feathers, but upon the way the light strikes them. It is the same with the beautiful tints we see on a soap-bubble. The film of water itself is colorless, but it becomes iridescent. You might divide all the colors of birds into two cla.s.ses--those that depend upon pigments in the feathers, and those that depend upon the play of light on the feathers."

"That's pretty hard to remember," said Nat; "but I know how a soap-bubble looks, though I never saw any birds look that way. Please show us one."

"I will show you two," answered the Doctor, who then went to his gla.s.s case, and took out a Wild Pigeon and a Hummingbird. "Look at the shining tints on the neck of this Pigeon, and see how the throat of this Hummingbird glitters when I turn it to the light."

"That's the prettiest color I ever saw," said Nat, "and I can remember about it now. But," he added, thinking of the way he had seen hens mope when they were moulting, "does it hurt birds to lose their feathers, uncle?"

"It is probably not as comfortable as being nicely dressed, and sometimes they seem quite miserable, especially if they shed old feathers faster than new ones can grow to replace the lost ones. Some birds, like Ducks, lose their wing-feathers all at once, and cannot fly for quite a while. But Heart of Nature is kind to his children, as a rule. Most birds shed their rowing feathers one at a time in each wing, so that they never lose their power of flight. Now this will do for wings, tails, and feathers. Come! what is the next thing you notice about this Sparrow? Is it entirely covered with feathers?"

"Of course it isn't," said Dodo; "it hasn't any feathers on its beak or on its feet, else how could it eat and hop about?"

"That is right. These parts of a Sparrow are bare; they never have any feathers; and the skin on them is hard and h.o.r.n.y, as different from soft thin skin as finger-nails. Now look at the beak, and think how many things a Sparrow has to do with it. He has no hands or paws, and so he must pick up everything he eats with his beak. He has no teeth, and so he must bite his food with his beak. He feeds on seeds like a Canary bird; so his beak comes to a sharp point, because seeds are small things to pick up; and it is very strong and h.o.r.n.y, because seeds are hard to crack, to get at the kernel. Notice, too, children, that his beak is in two halves, an upper half and a lower half; when these halves are held apart his mouth is open, so that you can see the tongue inside; and when the two halves are closed together the mouth is shut. These halves are called the _upper mandible_ and the _lower mandible_."

"Why, it's just like people's mouths," said Nat, "only people have lips and teeth."

"Certainly it is like our mouths. Birds are built like ourselves in a great many things, and live as we do in a great many ways. Bird People and House People are animals, and all animals must eat to live. A bird's beak is its mouth, and the under mandible moves up and down, like our chins when we eat or talk. Birds can talk as well as sing with their beaks. This Sparrow can say 'Peabody,' and some kinds of Parrots can repeat whole sentences so as to be understood. That is another thing in which birds' beaks are like our mouths. Now look again--can you see anything else about the Sparrow's beak?"

"I see a pair of little holes at the root of the upper mandible," said Rap.

"Well, those are the nostrils!" said the Doctor. "Birds must breathe, like ourselves, and when the beak is shut they breathe through the nostrils."

"So do I," said Dodo; and then she pursed up her pretty red lips tightly, breathing quite hard through her nose. "I do think," she said, when she had finished this performance, "birds have faces, with all the things in them that we have--there are the eyes, too, on each side, like people's eyes, only they look sideways and not in front. But I don't see their ears. Have birds any ears, Uncle Roy?"

"I can show you this Sparrow's ears. See here," said the Doctor, who had run the point of his penknife under a little package of feathers on one side of the back of the Sparrow's head, and lifted them up; "what does that look like?"

"It's a hole in the skin that runs into the head," said Nat. "Can birds hear through that?"

"Of course they can. Ears of all animals are made to hear with. This Sparrow can hear quite as well as you can, Nat. Now think, children, how many things we have found about this Sparrow's head that are quite like our own,--ears, eyes, nose, mouth, and tongue,--only there are no lips or teeth, because the h.o.r.n.y beak, with its hard edges and sharp point, answers both for lips and teeth. I want you to learn from this how many things are really alike in Bird People and House People, though they look so different at first sight. When we come to the bird stories, you will find that birds differ very much among themselves in all these things. I will show you all sorts of beaks, of different sizes and shapes. Here are pictures of several kinds of beaks--see how much they differ in shape! But they are all beaks, and all beaks are mouths. They all answer the same purposes in birds' lives, and the purposes are the same as those of our mouths. But now, what do you notice about this Sparrow's feet?"

"They are not a bit like my feet," said Dodo; "they are so long and slim and hard, and the toes stick out so all around. I think mine are nicer."

"But they would not be so useful as this Sparrow's if you had to live in a bush and hop about on the twigs," said the Doctor. "The bird's feet are fixed as nicely for that, as yours are for walking on the ground. I can show you, too, little girl, that a Sparrow's feet are a great deal more like yours than you think. Come, Rap! Tell me what you see about this bird's feet."

"Why, they are the ends of its legs, and there is a long slim part beyond the feathers, hard and h.o.r.n.y like the beak, and at the end of this are four toes, three in front and one behind, and they've all sharp claws on their ends."

"Very well said, my boy! Now I will show you that such feet as the Sparrow has are as much like Dodo's as a Sparrow's beak is like her mouth. Begin with the claws--"

[Ill.u.s.tration: 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 Woodp.e.c.k.e.r; 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.]

[Ill.u.s.tration: 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 h.o.r.n.y part stands up--I've noticed that in Canaries."

"But all this h.o.r.n.y 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?"

[Ill.u.s.tration: FIG. 1. Ordinary foot of perching birds; 2. Foot of Nighthawk, with a comb on claw of middle toe; 3. Climbing foot of Woodp.e.c.k.e.r, with two hind toes; 4. Grasping foot of Osprey, for holding prey.]

[Ill.u.s.tration: 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.]

"It's the heel in people, but I should think the hind toe of a bird was its heel," said Nat doubtfully, and beginning to think he did not understand.

"You might think so," said the Doctor; "but you would be wrong. All this h.o.r.n.y part that a bird stands up on is its foot. And the top of it, nearest to the feathers, is the heel. Don't you see, when I bend the foot _so_," continued the Doctor, as he bent the Sparrow's foot forward, "that the top of the h.o.r.n.y part makes a joint that stands out backward, in the same position your heel always has? All this slender h.o.r.n.y part of the foot, above the roots of the toes, corresponds to the instep of your foot, and of course the heel comes next. You must remember the name of it--the Wise Men call it the _tarsus_."

"Then hasn't a bird got any legs, Uncle Roy, only just feet?" asked Dodo.

"Oh! yes; legs too, with a knee-joint and a hip-joint, like ours. But all these parts are up closer to the body, and hidden by the feathers, so that you cannot see them."

As the Doctor said this there was a great commotion. Quick, who had been watching the mouse hole all the while, gave a sharp bark and pounced on something. There was a feeble squeak, and it was all over with a mouse which had ventured too far from its hole.

"Poor little mousey!" said the Doctor, as he took the limp body from the terrier's mouth. "It is quite dead. I am sorry, but it might have nibbled some of my birds. Besides, this is exactly what I wanted to teach you something about. Who can tell me the difference between a mouse and a Sparrow?"

"I can!" said Dodo; "it's all difference; a mouse hasn't any feathers, or any wings, and it has four feet, and a long tail and whiskers and teeth--"

"That will do, little girl, for differences; do you see anything alike between a Sparrow and a mouse, Rap?"

"I think the fur is something like feathers, Doctor," answered Rap; "and you told us how a beak was like a mouth without any teeth or lips; then a mouse has four feet and legs; but a bird has only two feet, and two wings instead of four legs and feet like a mouse."

"That is just what I want you all to think about," said the Doctor. "Now listen. If a Sparrow has a pair of feet that correspond to a mouse's hind feet, what do you think a Sparrow's wings correspond to in a mouse?"

"I should think they would be something like a mouse's fore feet,"

answered Rap, after thinking a moment.

"That is exactly right. Birds and beasts are alike in many respects.

They have heads, necks, and bodies; they have tails; and they have limbs. Beasts have two pairs of limbs. We call them fore legs and hind legs. People have two pairs also. We call them arms and legs. So you see our arms correspond to the fore legs of beasts, though we never use them for moving about, except when we go on our hands and knees, or climb trees, or swim in the water. And as for birds--why, their fore limbs are turned into wings, to fly with, so that they walk or hop on their hind limbs only, just as we do. Animals that go on all fours are called _quadrupeds_. Animals that go on their two hind limbs only, like Bird People and House People, are called _bipeds_. A Sparrow's wings are just as much like a mouse's fore legs, as a Sparrow's feathers are like a mouse's fur."

"How funny!" said Dodo. "But how are a bird's wings like fore legs, when they haven't got any paws or toes--or fingers--or claws--only just long feathers?"

"They have fingers, and some birds' wings have claws; only you cannot see them, because they are all wrapped up in the skin and covered over with the feathers. Some day--not to-day, because you have had a long lesson already--I will show you a bird's wing with only its bones. Then you will see that it has finger-bones at the end, then hand-bones next, then bones that run from the wrist to the elbow, and then one bone that runs from the elbow to the shoulder--almost the same bones that people have in their fingers, hands, wrists, and arms. So you see wings are the same to a bird that fore legs are to a mouse or arms are to us.

"I could go through all the inside parts of birds, and show you something like the same parts in people,--stomach and bowels, to take care of the food they eat and turn it into blood to nourish them; lungs to breathe with, and keep the blood pure; heart to beat and thus pump the warm blood into all parts of the body; brain and nerves, which are what birds think and feel with, just as we do with ours; and all their bones, which together make what we call the _skeleton_, or framework of the body, to keep the flesh in shape and support the other organs."

"Dear me!" sighed Dodo; "there must be ever so many more things inside of birds that we can't see, than there are outside."

"Of course there are!" said the Doctor. "It won't be very hard for you to remember the outside parts, and learn the names of them all. I have told you most of them that you need to remember, to understand the stories I am going to tell you about birds. See here! What do you think of this?"