THE MOLT 
85 
form they fit the bird for locomotion (see beyond, under Uses of the 
Wing and Tail) or in color adapt it* to the special needs of its haunts 
and habits. In the first place, however, the field student should have 
some knowledge of the laws of feather change included under the general 
term of molt. 
The Molt . — When hatched, a Passerine bird is naked except for a 
scanty growth of filmy down on the feather tracts of the upper half of 
the body. This is the ‘natal down’ of Dwight COO) whose terminology 
I adopt. The natal down is quickly succeeded by the ‘juvenal’ or nest- 
ling plumage, which is sufficiently grown in from eight to fourteen days 
to enable the bird to leave the nest. The tail is still only about half- 
grown and the wings, as a rule, barely large enough to permit of short, 
uncertain flight. 
Some birds (e. g. Sharp-tailed and Seaside Sparrows) wear this juvenal 
or nestling plumage between two and three months, but most species 
lose it shortly after leaving the nest. In either case, it is followed by 
the first winter plumage, which is acquired by molt (post juvenal) 
of all the body feathers, most of those of the wings and tail usually 
being retained. If the young bird now resembles its parent, their 
plumage changes are thenceforth the same. 
In the fall all birds molt, but in the spring there is no regularity 
as to feather renewal, even among closely related species. The Bobo- 
link and the Sharp-tailed Sparrow have a complete spring molt (pre- 
nuptial), even to the wings and tail; the Scarlet Tanager and Gold- 
finch molt only the body feathers; other species acquire some new 
feathers about the head and chin, and with many there is no feather 
growth at this season, the differences between the winter and breeding 
plumages being due to wear or fading. 
After the breeding season, all adult birds pass through a complete 
molt (postnuptial), and the bird is again in winter plumage. 
In its simplest form, and ignoring the comparatively few cases in 
which an essentially adult plumage is not acquired at or before the first 
prenuptial (spring) molt, the molt among the Passeres may be summar- 
ized as follows: (1) Natal down, lost by postnatal molt which brings 
the (2) juvenal or nestling plumage; lost by post juvenal molt which 
brings the (3) first winter plumage; lost to a greater or less extent in 
some species by prenuptial molt which brings the (4) nuptial plumage; 
lost by postnuptial molt which brings the (5) second and subsequent 
winter plumages. 
With some minor variations this is the general order of molt among 
other than Passerine birds. Except the Ducks and Ptarmigan all birds 
have a complete postnuptial molt, and with many Snipe the spring or 
prenuptial molt is complete. Some Snipe wear the juvenal plumage 
until winter or even until the prenuptial molt, the post juvenal molt 
being omitted. 
Among the praecocial Gulls, Terns, Ducks, Shore-birds and Galli- 
naceous birds the natal down thickly covers the body and the chick 
