Peculiarities of Birds 107 



carrion. Singing birds devour an innumerable multitude 

 of caterpillars and insects. 



Birds in proportion to their size require much more food 

 than mammiferous animals, and thus become much more 

 useful. Many species of birds serve mankind for food ; 

 and their eggs are both nutritious and pleasant. Their 

 plumage serves partly for warmth and partly for orna- 

 ment. Many delight us with the exquisite modulation of 

 their notes ; nor is our admiration less excited by the skill 

 displayed in the construction of their nests. 



The migratory habits of various birds are also highly 

 deserving of our notice. Some are only partially migra- 

 tory, removing from one district or locality to another, as 

 from the borders of the sea into the interior of the country, 

 or from the mountains to the plains or vice versa. Others 

 remove to a distant country, like the stork, which is found 

 in Holland in the summer, but makes its winter abode in 

 Egypt and Barbary. The swallow tribe quit this country 

 and other parts of Europe in the autumn, and pass in 

 large troops over to Africa ; they arrive in Senegal early 

 in October. 



But many birds, which among us are birds of passage, 

 are stationary in the milder climate of Palestine, and 

 never leave the place of their birth, unless for a very short 

 time. The number of species of birds is much greater 

 than that of quadrupeds ; many of them also are very 

 long lived. The swan is said to attain the age of a hun- 

 dred years. 



The organs of breathing in birds are admirably con- 

 structed for the purpose of enabling them to fly with 

 greater ease. The air passes through their lungs into air- 

 cells, which either surround or are joined to the heart and 

 liver, and other internal parts ; there are even air-cells in 

 the bones, which are supplied in the same way. In the 

 Wild Swan (Cygnus ferus) the wind-pipe, after passing 

 down the long neck of the bird, is curiously coiled up 

 withiu the breast-bone for the same purpose. Naturalists 

 state that in the Tame Swan (Cygnus olor) the trachea does 

 not make this convolution. 



There is a closer resemblance than appears at first sight 



