Renewal of Feather Covering o 



habits of the bird." It is thus evident that if a bird were provided with only a 

 single set of feathers, they would ultimately become so worn and frayed as to be 

 useless, either as a covering for the body or for flight. By a wise provision of 

 nature, the entire feathering is renewed at periodic intervals. This renewal 

 known as the moult, takes place normally once a year, usually after the arduous 

 duties of rearing the young are over ; but there are numerous exceptions to this, 

 some birds acquiring two, three, or exceptionally even four, more or less com- 

 plete annual changes of plumage, and further, these moult periods " must not be 

 confounded with occasional new growth at any time and anywhere to replace 

 feathers accidentally torn out." In order that the ordinary activities may not 

 be seriously interfered with during the period of moult, there is a distinct relation 

 between the feather loss and feather gain, most birds at no time being deprived 

 of either the power of flight or the protection afforded the body by the feathers, 

 and furthermore this fall and replacement is more or less synchronous from the 

 Opposite sides of the body. Thus in probably all of the great group of Passerine 

 birds, the moult of the flight feathers begins in the middle of the wings with the 

 practically simultaneous fall of the proximal or innermost primary on each side. 

 As soon as the old feather has fallen, the new-forming feather pushes into view, 

 and grows rapidly, and by the time the expanded portion of the feather itself is 

 . breaking from the apex of the follicle the next primary falls, and so the renewal 

 by pairs proceeds outwards. With the secondaries the renewal proceeds in the 

 opposite direction, that is the outer or distal one on each side falls first, this loss 

 being very nearly coincident with the fall of the fifth or sixth primary, and their 

 replacement by pairs proceeds towards the body. In some cases, as in Ducks, 

 Geese, Swans, and Flamingos, the wing-quills are all shed at once, thus rendering 

 the birds practically helpless for a short time, but this is very exceptional. The 

 feathers of the tail are also normally renewed in pairs, the central pair falling 

 first, followed by the quills next adjacent on either side. The process, however, 

 is much more rapid than in the wings, for by the time the outer pair has fallen 

 the middle ones are often not half grown. The renewal of the body feathering 

 is in less obvious sequence, though " the moult regularly begins at fairly definite 

 points in the feather tracts, radiating from them in such manner that the outer 

 rows of feathers where the tracts are widest, and their extremities are normally 

 the last to be replaced." DWIGHT. 



Renewal of Parts other than Feathers. Although the renewal of the plu- 

 mage is the most important event of this kind, the feathers are by no means the 

 only part of the integument that is periodically changed. Thus in certain Grouse 

 the claws or pectinations along the sides of the toes become greatly lengthened 

 in winter and are partially shed or worn down in spring and summer ; the Puffins 

 and Auklets shed portions at the base of the bill and around the angle of the 

 mouth; the Penguins, or at least the King Penguin, moults the bright orange- 

 colored membrane at the base of the bill; the American White Pelican develops 

 a curious appendage on the upper mandible which is shed at the close of the nest- 

 ing period. These phenomena and others of similar character will be more fully 

 described under various forms exhibiting them. 



