574 Animal Biology 



Class Aves (Birds) (Fig. 154) 



Plumes and feathers are used for millinery purposes. Feathers are 

 also used in manufacturing pillows. The flesh and eggs of domestic 

 and game birds are used as food. Poultry products are valued at mil- 

 lions of dollars annually in the United States. Excretions and ejecta of 

 certain species of birds are known as guano, which is used as fertilizer 

 because of its high content of nitrogen and phosphoric acid. Game 

 birds are a source of a great amount of sport. The equipment necessary 

 for hunting them requires quite an expenditure of money when the en- 

 tire country is taken into consideration. Certain birds are beneficial 

 by destroying injurious animals, such as field mice, rabbits, ground 

 squirrels, and insects, as well as the seeds of weeds. Other birds are 

 detrimental because they destroy valuable animals as well as important 

 plant and grains in large numbers. 



Class Mammalia (Mammals) (Fig. 156) 



The relations of mammals in general to man are so complex and 

 varied that only a general account and a few suggestions can be given. 

 More detailed books are suggested for reference studies. 



Domestic animals are used extensively and for a variety of purposes. 

 Cattle supply milk, meat, skins, hair, and hoofs. The cattle industry is 

 one of the most important animal industries in this country. Sheep 

 supply meat and wool for the manufacture of woolen garments. Goats 

 serve as draft animals and as a source of meat and milk. Camels serve 

 as draft animals and supply hair for the manufacture of fabrics and 

 brushes. The llama is used for transportation in South America. The 

 elephant is used for transportation and general labor. It supplies us 

 with ivory. The dogs serve a great variety of purposes from the useful 

 to the ridiculous. The dog was probably one of the first animals to be 

 domesticated. Could man have selected a more faithful companion and 

 ser\^ant? 



Leather is made by "tanning" the hides of a number of animals, par- 

 ticularlv those of cattle. Manv animals are utilized in the manufacture 

 of fertilizers. The horns and hoofs of animals are used in making glue. 

 The skins of such animals as the otter, mink, weasel, marten, badger, 

 wolverine, muskrat, skunk, fox, lynx, raccoon, and rabbit are used as 

 sources of the various kinds of furs. 



The destructive habits of such animals as rats, mice, and rabbits are 

 well known and need not be discussed. 



