EXTERNAL PARTS OF BIRDS. — FEATHERS. 91 



between these two sets of feathers has already been fully shown. Down is scanty, leaving 

 much or all of the body naked, in most altricial birds, or such as are reared by the parents 

 in the nest (Lat. alirix, female nourisher) ; but thick and puffy in some Altrices, and in all 

 Prcccoces (Tiat. prcecox, precocious), which run about at birth. Since many birds which re- 

 quire to be reared in the nest also hatch clothed, or very speedily become downy, a more 

 exact distinction may be drawn by using the terms ptilopccdic and psUopcedic (Gr. irriXov, ptilon, 

 a feather; -^CKoi, psilos, bare ; and Trals, pais, a child) respectively for those birds which hatch 

 feathered or naked; a chicken and a canary-bird are familiar examples. Ptilopaedic birds are 

 also called dasypasdic (Gr. baavs, dasus, hairy), which means the same thing. It is the rule, 

 that the higher birds are born helpless and naked or nearly so, requiring to be reared in the 

 nest till their true feathers grow ; the reverse with lower birds, as the walking, wading, and 

 swimming tribes; and a primary division of birds has even been proposed upon this physio- 

 logical distinction. It offers, however, too many exceptions ; thus, no birds are more naked 

 and helpless at birth than young Cormorants. Probably all prsecocial birds are also ptilopa3dic 

 and all psilopaedic birds altricial ; but the converse is far from holding good, many Altrices, as 

 Hawks and Owls, being also ptilopsedic. In other words, psilopsedic birds are always altricial, 

 but ptilopadic birds may be either altricial or praecocial. In view of this distinction which 

 does not always distinguish, it has been proposed to drop the terms, and substitute nidicolous 

 (Lat. nidus, nest, and colere, to inhabit) for those birds which stay some time in the nest, those 

 which leave it at once being termed nidifugous (Lat. nidus, nest, and fugere, to flee). Thus, 

 all Altrices are NidicolcB, and all PrcBCOces are Nidifugce ; in either case without prejudice to 

 the question whether the former are psilopsedic or ptiloptedic. 



In any ease, true feathers are soon gained, in some days or weeks, those of wings and tail 

 being usually the first to sprout. The acquisition of plumage is called endysis (eudva-is, endusis, 

 putting on). The renewal of plumage is a process familiar to all, in its generalities, under the 

 term " moult," or ecdgsis (Gr. €k8v(tis, ekdusis, putting off), though the details of the process 

 have been worked out satisfactorily for comparatively few species of birds, and M'e have to be 

 cautious in making statements concerning this subject; for unexpected exceptions may be un- 

 provided for unless our language is guarded. Feathers are of such rapid growth, and make 

 such a drain upon vital energies, that we easily understand how critical are periods of moult. 

 The first plumage is usually worn but a short time ; then another more or less complete change 

 commonly occurs. The moult is annual, as a rule ; and in many cases more than one moult is 

 required before a mature bird attains the perfection of its feathering. It is well known how dif- 

 ferent many birds are the first year in their coloration from that afterward acquired; sometimes 

 changes progress for several years ; and some birds appear to have a period of senile decline. 

 All such changes are necessarily connected, if not with actual moult, as is the rule, then at any 

 rate with wear and tear and repair of the plumage. The first plumage having been gained, 

 under whatever conditions peculiar to the species, it is the general rule, that birds are there- 

 after subject to single, or annual, moult ; possibly there is no exception to the rule that a 

 healthy adult bird renews its plumage at least once a year. This change commonly occurs 

 when the duties of incubation are concluded, and the well-worn plumage most needs renewal, 

 as happens in late summer and early autumn months in our latitudes ; though some of our 

 l)irds, as Swallows and Hawks, may put off tlie process till winter. Many birds, however, 

 moult twice a year, the additional moult usually occurring in spring, when a fresh nuptial suit 

 is acquired ; in such cases, the moult is said to be dotible, or semi-annual. Such additional 

 moult is generally incomplete; that is, all the feathers are not shed and renewed, but more or 

 fewer new ones are gained, with more or less loss of old ones, if any. The most striking orna- 

 ments donned for the breeding season, as the elegant plumes of many Herons, are usually worn 

 but a brief time, being doffed in advance of the general fall moult; and males of very many 

 birds which put on special nuptial ornaments make room for these by doffing feathers from the 



