Because the bird _lives by suction_, dipping its broad bill in search of aquatic worms, mollusks, insects and the roots of weeds. The bill forms _a natural spoon_, and the muscular points enable the bird to _filter the mud_, and to retain the nourishment which it finds. 1046. _Why has the spoon-bill long legs?_ Because it _wades in marshy places_ to find its food. Its legs are therefore long, for the purpose of keeping its body out of the water, and above the smaller aquatic plants, while it searches for its prey. 1047. _Why have the parrots, &c., crooked and hard bills?_ Because they live upon nuts, the stones of fruit, and hard seeds. The shape of the bill, therefore, enables them to _hold the nut or seed firmly_, and the sharp point enables them to _split or remove the husks_. 1048. _Why can a parrot move its upper as well as its lower bill?_ Because by that means it is enabled to bring the nut or seed nearer the fulcrum, or joint of the jaw. It, therefore, acquires greater power, just as with a pair of nut-crackers we obtain increased power by _setting the nut near to the joint_. 1049. _Why have animals with long necks large throats?_ Animals that graze, or feed from the ground, generally have a more powerful muscular formation of the throat than those which feed in other positions, because a greater effort is required to _force the food upward, than would be needed to convey it down_. 1050. _Why are the bones of birds hollow?_ Because they are thereby rendered _lighter_, and do not interfere with the flight of the bird _as they would do if they were solid_. Greater strength is also obtained by the _cylindrical form of the bone_, and a larger surface afforded for the _attachment of powerful muscles_. [Verse: "And my hand hath found, as a nest, the riches of the people; and as one gathereth eggs that are left, have I gathered all the earth; and there was none that moved the whip, or opened the mouth, or peeped."--ISAIAH X.] 1051. _Why do all birds lay eggs?_ Because, to bear their young in any other manner, would _encumber the body_, and materially interfere with their powers of flight. As soon as an egg becomes large and heavy enough to be cumbersome to the bird, it is removed from the body. A shell, impervious to air, protects the germ of life within, until from two to twenty eggs have accumulated, and then, although laid at different intervals, their incubation commences together, and the young birds are hatched at the same time. CHAPTER LIII. 1052. _Why have birds with long legs short tails?_ Because the tails of birds are used to guide them through the air, by a _kind of steerage_. When birds with long legs take to flight, they throw their legs behind, and they then _serve the same purpose as a tail_. [Illustration: Fig. 68.--PERCH.] 1053. _Why have fishes fins?_