172 



REPTILES AND BIRDS. 



more elongated than the others. The row of feathers bordering the 

 wing behind is known as the alar quills, or wing quills, and those 

 terminating the extremity of the tail, as caudal quills. From the 

 head, backwards to the tail, the body feathers increase in strength 

 and size, also alter in form ; those on the face, or round the base of 

 the bill, being smallest (Fig. 53), the tail-coverts longest (Fig. 54). 

 Immediately covering the base of the wing quills are a row of feathers 

 on both surfaces of the wing ; these are the quill coverts. 



The most brilliant feathers are found in Birds of warm climates. 

 In many species the brilliant plumage is confined to the males, while 

 that of the females is dark and sombre. In other cases it is the 



Fig. 52.— Plumule. 



Fig. 53- — Neck covert. 



Fig. 54. — Tail covert. 



same in both sexes. The young of some species attain the adult 

 appearance after the first moult ; others take several years to acquire 

 their full splendour. 



Birds cast their feathers at least once a year. This is called 

 moulting, and usually occurs in the autumn, but sometimes both in 

 spring and autumn. During the moulting season Birds are dull, 

 retiring, and silent ; but when they emerge from this state they 

 proudly display their brilliant plumage, which sometimes rivals the 

 gayest flowers. 



Among the Gallinaceous Birds, and especially among the aquatic 

 species, there exist over the coccyx certain receptacles which distil 

 the oily substance with which they lubricate their plumage. These 

 receptacles are known as the uropygial glands. On its lower surface 



