T HE BIRDS 405 



Some hawks catch chickens, although the great majority are beneficial 

 because they destroy harmful rodents, and we should kill only those 

 known to be harmful. Some birds, like the English sparrows, live a 

 little too intimately associated with man and may be a general nuisance 

 and cause quite a mess around the place. 



As a whole, however, we must consider the birds great friends of man 

 and give them protection. Excessive clearing of the land will remove 

 the trees and protected places on the ground where birds may build their 

 nests and, thereby, reduce their numbers. Reforestation and protection 

 of existing forests conserve our birds as well as our timber. Game laws 

 are set up to help protect our game birds and should be rigidly respected. 



Characteristics of Birds 



Feathers are the most distinguishing feature of birds ; all birds have 

 feathers and no animals except birds have feathers. There are three 

 kinds. Those seen from the outside are the large contour feathers, which 

 consist of a central shaft with parallel barbs to the sides. These give 

 shape to a bird's body and those on the wing are spread to offer re- 

 sistance to the air, while those on the tail form a rudder by means of 

 which the bird controls the direction of its flight. The down feathers 

 consist of a central shaft with the barbs coming out irregularly so as to 

 form a soft fluffy tangle. They are found under the contour feathers 

 and help hold the warmth of the body. There is no material known that 

 is more efficient for holding heat than down. We take advantage of this 

 by making quilts of down, which may be very light yet cozy and warm 

 on the coldest nights. The down feathers are very abundant in the 

 ventral posterior region of the body and are not covered with contour 

 feathers in this region because this part of the body covers the eggs and 

 keeps them warm when a bird is sitting on a nest. Some duck hunters 

 say that it is best to let a duck fly over you and shoot him from the rear, 

 for the bullets can penetrate this soft downy region much better than the 

 tough contour feathers at the front of the body. Some feathers may be 

 a mixture of the two, downy near the body and contour in type on the 

 outside, and, thus, serve a dual function. The filoplumes are little hair- 

 like projections from the skin that seem to have no particular purpose, 

 but make it harder to pick a chicken. 



Birds are warm-blooded animals. These are the first of the animal 

 groups studied that have this characteristic. Those up to this point are 

 called cold-blooded. This term is confusing because it does not mean 

 that they have cold blood necessarily. It simply means that the tem- 

 perature of the body, including the blood, varies according to the sur- 



