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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 23

a definite, regular course from which normally there is
little variation. Many birds have a complete molt at the
close of the breeding season. A few, like the swallows and
some birds of prey, have the annual molt during winter.
Some sandpipers and plovers molt from a breeding plum-
age into a fall or winter dress, and then sometime during
the winter change again into another breeding plumage.
Summer and winter plumages may be alike, as in the
swallows, or entirely different, as in the male scarlet
tanager, which exchanges its brilliant red breeding dress
for olive-green in winter, though wings and tail remain
uniformly black throughout the year.
The ducks of the Northern Hemisphere also exhibit a
peculiarity in color variation. Most male ducks wear a
bright-colored breeding dress, well exemplified in the
brilliant-green head and chestnut-brown breast of the
male mallard. In June, at the close of the breeding sea-
son, these males molt and assume a dull plumage called
the "eclipse plumage," very similar to that of the female,
and which they retain during the period of wing molt. In
the fall most species replace the dull plumage with the
bright-colored dress that is carried into the next breeding
season. The ruddy duck and the blue-winged teal, how-
ever, carry the eclipse dress longer. Some have considered
this dull plumage a wise provision of nature to protect the
male during the flightless period, while others have be-
lieved it merely a repetition of an early type of plumage.
Curiously, eclipse plumage is not known in the ducks of the
Southern Hemisphere.
Under unusual circumstances the eclipse plumage may
be omitted. A male mallard which Dr. J. C. Phillips con-
fined in a cold room all summer did not attain the eclipse
plumage but when brought into normal surroundings in
the fall molted directly into the bright-colored dress usual
at that period. I have studied adult male ducks affected
by a sickness from which they recovered but that served
to retard the plumage change so that the summer molt
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