BIRDS 



157 



nestlings and found among the contour feathers of the 

 adult but not showing on the surface ; (4) the pin feathers, 

 which are hair-like, and which are removed from a plucked 

 bird by singeing. The contour feathers are similar in 

 structure to the quill feathers. They protect the body 

 from blows, overlap so as to shed the rain, and, with the 

 aid of the downy feathers retain the heat, thus accounting 

 for the high temperature of the bird. The downy feathers 

 are soft and fluffy, as they possess few or no barbicels ; 

 sometimes they lack the rachis (Fig. 293). The pin feath- 

 ers are delicate horny shafts, greatly resembling hairs, but 

 they may have a tuft of barbs at the ends. 



A feather grows from a small projection (or papilla) found 

 at the bottom of a depression of the skin. The quill is 

 formed by being molded around the papilla. Do you see 

 any opening at the tip of the quill for blood vessels to enter 

 and nourish the feather ? What is in the quill ? (Fig. 291.) 

 The rachis ? A young con- 

 tour or quill feather is in- 

 closed in a delicate sheath 

 which is cast off when the 

 feather has been formed. 

 Have you seen the sheath 

 incasing a young feather in 

 a molting bird ? 



There are considerable 

 areas or tracts on a bird's 

 skin without contour feath- 

 ers. Such bare tracts are 

 found along the ridge of the breast and on the sides of 

 the neck. However, the contour feathers lie so as to over- 

 lap and cover the whole body perfectly (Fig. 294). 



The shedding of the feathers is called molting. Feathers, 



FIG. 294. DORSAL AND VENTRAL 

 VIE\V OF PLUCKED BIRD, showing 

 regions where feathers grow. 



