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Wetmore, Alexander, 1886-, et al. / Warm-blooded vertebrates

Chapter II: adaptations for progression by flying ,   pp. 13-24 ff. PDF (4.7 MB)

Page 22

In the ordinary form of molt, feathers fall a few at a
time and new ones begin immediately to appear in their
places. As these new feathers grow, other old plumes fall
and are in turn renewed. Thus the molt continues from
four to six or more weeks, during which the bird may pre-
sent an extremely ragged appearance, though at no time
is its body predominantly bare. The wing illustrates ef-
fectively this regular sequence of shedding and regrowth,
there being at no time any large gap in the feathers, so that
the ability to fly is maintained throughout the entire
molting period-a matter of great importance to a creature
largely dependent upon its wings for transportation and
for escape from its enemies.
Ducks and geese, however, as well as rails, flamingos,
and grebes, have an entirely different wing molt from that
just described. In these birds all the wing quills, with
even the smaller feathers known as wing coverts, fall at
practically the same time, so that the wing is almost bare,
leaving the bird for a month or more entirely flightless
(Plate 9). During this period, ducks, geese, grebes, and
rails resort for safety to marshes, where they hide in rushes
or other dense growth; in the northern tundras, where
many ducks and geese breed, they retreat to small open
ponds or lakes where they may hope to remain unnoticed.
In this flightless state these birds are known as "flappers,"
a word that describes their condition accurately, since
when alarmed they dash off across the water with rapidly
beating wings, traveling so fast that they are usually
hidden in the rushes before one realizes their true condi-
tion. Molting takes place in ducks and geese from July
to September, during which flappers are only rarely seen.
After five weeks or so of seclusion they appear once more
in the open. In Canada geese the wing molt in the parents
comes soon after the young hatch, so that both young and
old mature their wing feathers and gain the power of
flight at the same time in late summer.
The progress -of the molt in each species of bird follows
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