BIRDS 293 



hand and wrist, the third and fourth fingors are absent while the wrist bones 

 and fingers of the fowl have grown together, thus giving greater strength 

 and support. This is evidently an adaptation for fliglit. 



Feathers. — Few people realize that the body of a bird is not com- 

 pletely covered with feathers. Look for featherless areas on the body of 

 the bird you are working with. Notice that feathers are of several shapes. 

 Soft down feathers cover the body, serving for bodily warmth. In the 

 wings we find quill feathers; these are adapted for service in flight. Let us 

 examine a single quill feather more closely. The main axis of the feather, 

 called the shaft, is hollow, light, and strong. Ywrnx the shaft, lateral 

 branches, called barbs, are given off". The barbs give rise to still smaller 

 lateral structures, the barbules, the latter just visible to the naked eye. Each 

 barbule is interlocked with its neighbor by means of many microscopic hooks, 

 the barbicels. If you attempt to pull apart the barbs of a feather, you 

 will find that they stick together. What is the reason for this? Slight 

 this arrangement be of use in flight, and if so, how? 



Draw a quill feather and show all the parts visible to the naked eye. 



Feathers. — Feathers are developed from the under layer of 

 the skin. At first they appear to be tiny, pimplelike projections. 

 They are formed in almost exactly the same manner as are the 

 scales of a fish or a lizard. The first feathers developed on the 

 body are evidently for protection against cold and wet. In 

 aquatic birds the feathers are oiled constantly, and thus shed 

 water. The feathers of most male birds are brightly colored. 

 This seems to make them attractive to the females of the species; 

 thus the male may win its mate. 



Perching. — The habit of perching is an interesting one. In 

 many perching birds the tendons of the leg and foot, which regu- 

 late the toes, are self locking ; thus while asleep such birds 

 balance themselves perfectly. A certain part of the ear, known 

 as the semicircular canals, has to do with the function of balanc- 

 ing. In the flamingoes, which do not perch, balancing appears to 

 be automatic and self-regulating; thus the bird is able to go to 

 sleep when in an upright position. 



Tail. — The tail is sometimes used in balancing; its chief func- 

 tion, however, appears to be that of a rudder during flight. Note 

 that the tail is merely a small protuberance of the body, the 

 feathers which grow there give it the shape. In many birds, under 

 the skin of the tail is located a large oil gland, whence comes 

 the supply of oil that is used in waterproofing the feathers. 



Adaptation in the Lower Limbs. — In the leg identify the thigh, the shin, 

 and foot. The ankle of the bu-d is extremely long, the seven bones found 



