This remarkable creature is found in Southern and Eastern Australia, and also in Tasmania. It is not at all uncommon, but is seldom seen, for it spends most of its time in the water, or else in its burrow, which is always made in the bank of a pool or stream. This burrow is generally a long one, running to a distance of forty or even fifty feet, and terminates in a large chamber, which is used as a nursery. And it always has two entrances, one below the surface of the water and one above, so that if the animal is alarmed in any way it can run in by one door and out again by the other. Two eggs are laid by this most curious creature. They measure about three-quarters of an inch in length, and are enclosed in a tough white shell. How they are hatched nobody seems quite to know; but when the little ones first make their appearance they are quite blind and quite naked, and have hardly any beaks at all. When fully grown the duckbill is about eighteen inches long from the end of the snout to the tip of the tail. BIRDS CHAPTER XX BIRDS OF PREY We have now first to think of the great class of the birds, which are distinguished from all other living creatures by having their bodies covered with feathers. These feathers serve a double purpose. [Illustration: TYPICAL BIRDS OF PREY. 1. Red-tailed Buzzard. 2. Sparrow-hawk. 3. Golden Eagle. 4. Great Horned Owl.] In the first place, they help to preserve the warmth of the body. Birds are hot-blooded animals--indeed, their blood is a good deal warmer than ours--and they often have to fly very fast through very cold air. So, you see, it is most important that they should be clothed with some sort of covering which is very warm and at the same time light. And nothing is warmer, and at the same time lighter, than a coat of feathers. And then, in the second place, many of these feathers are most useful in flight. Without them, indeed, a bird could not fly at all. If we want to keep a tame bird from escaping, we have only to clip its wings, and then it can no longer raise itself into the air. But it is not only the feathers of the wings that are used in flight; those of the tail are employed as well, for they assist in flight, especially in checking speed, and serve as a rudder, enabling the bird to steer its way through the air. Now birds are divided into orders and tribes and families, just as the mammals are. But scientific men are not quite sure which of the orders ought to be placed first. Among the birds of prey, however, we find some of the largest and finest and most powerful of all the feathered race; so that we cannot do better than place these at the head of our list.