BIRD 



729 



BIRD 



"iRD, an animal with feathers that 

 is the briefest description that can be given, 

 and at the same time one which will enable a 

 person to recognize a bird wherever seen. Of 

 course many more facts must be known if one 

 is to have even the most general knowledge of 

 birds that they are warm-blooded, that each 

 has a backbone and but two legs, and that most 

 of them can fly. This last feature might at first 

 seem the truly distinguishing one, but a little 

 thought brings to mind the fact that some 

 birds, as the ostrich, the penguin and the 

 curious apteryx, cannot fly, while bats, which 

 are not birds, flying squirrels and flying fishes 

 do have the power of flight. 



That birds have backbones show that they 

 belong in the great class of vertebrates, for 

 vertebrate means backboned. But it is very 

 curious to an untrained person to learn that 

 they are much more closely related to the 

 reptiles than to any other living animals. 

 There seems to be absolutely no resemblance 

 between the brilliantly-colored bird, with its 

 exquisite song, poised lightly on tree or bush, 

 and the venomous snake which slips stealthily 

 through the underbrush, perhaps intent on 

 robbing the nest of that very bird. One is 

 perhaps the most dearly-loved by man of all 

 the animal world; the other the most hated 

 and feared. Yet scientists discover resem- 

 blances in their structure, and students of fossil 

 forms can state positively that ages ago there 

 were bird-reptiles or reptile-birds from which 

 existing birds developed. 



Framework of the Body. The most natural 

 thing in the world is to think, "Since a bird 

 can fly, its body must be light," and so indeed 

 it is. For the bones are thin and hollow, and 

 in the thorax and abdomen are air cavities 

 which can be inflated when the bird wants to 

 fly. Everyone who has watched a housewife 

 prepare a fowl for the table knows the shape 

 of the breastbone, which is really a keel to 

 which are fastened the strong wing-muscles. 

 All birds that fly have this keel-like breast- 

 bone, and the lowest classes of birds, as the 

 ostrich, which do not have it, are called ratitae, 

 meaning keelless or flat-bottomed boat. 



Flight. It is the modification of the fore 

 limbs or "arms" of birds into wings which gives 

 them their most wonderful distinction the 

 power of flight. From the "arms and hands" 

 as they may be called, grow strong heavy 

 feathers, making a broad surface with which 

 the bird can beat the air; while above and 

 below these heavy quills there are short feath- 

 ers which prevent the air from passing through. 

 The great condor has a wing-stretch of from 

 ten to twelve feet, while that of the humming 

 bird is from two to about five inches, but 

 each is perfectly adapted to bearing up the 

 body which it must support. The tail does not 

 help much in flight, but is rather a rudder by 

 which the bird steers itself and holds its body 

 level. 



And the power of flight to which all these 

 special structures contribute is marvelous 

 indeed. The grace of a bird in soaring, hover- 

 ing, sailing and swooping, everyone has 

 remarked, and poets have often found in it 

 their inspirations. Thus Leland has 



Great albatross ! the meanest birds 



Spring up and flit away, 

 While thou must toil to gain a flight, 



And spread those pinions gray ; 

 But when they once are fairly poised, 

 Far o'er each chirping thing 

 Thou sailest wide to other lands, 



E'en sleeping on the wing ; 



and Shelley sings 



Around, around, in ceaseless circles wheeling 

 With clang of wings and scream, the Eagle sailed 

 Incessantly. 



The flight of smaller birds, too, has had its 

 strain of praise, for Riley tells of 



. . . the humming-bird that hung 



Like a jewel up among 



The tilted honeysuckle horns. 



and Christina Rossetti sings to the skylark 



O happy skylark springing 

 Up to the broad, blue sky, 

 Too fearless in thy winging. 



It does not seem strange that the giant birds 

 that seem to hang motionless for hours in the 

 upper air should be able to take long, swift 

 journeys in search of food or a new abiding 



