Although after they have grown to a third

Although
penguins go through molting, usually annually, there is exception. Galápagos penguin,
which usually goes through two molts per
year. The adult emperor penguins can be recognized by deep dorsal black
feathers and parts of flippers and tail. The ventral wings and belly are white
and the upper breast is yellow. The upper mandible is about three inches long.
The lower mandible is pink (Williams, Tony D. 1995). In juveniles, the auricular patches, chin and throat are
white, while its bill is black. 

The emperor penguin’s
dark plumage fades to brown from November until February (the Antarctic
summer), before the yearly molt in January and February.  Molting is
rapid in this species compared with other birds, taking only around
34 days. Emperor penguin feathers emerge from the skin after they have
grown to a third of their total length, and before old feathers are lost, to
help reduce heat loss. New feathers then push out the old ones before finishing
their growth.

Emperor penguin feathers emerge from the skin
after they have grown to a third of their total length, and before old feathers
are lost, to help reduce heat loss. Fresh feathers emerge out and the old ones
move out, and thus completes its formation.

The month
of November and February are months of Antarctic summer. During this time, the
feathers changes its color, from dark to brown to yellow. However, January and
February, the molt happen completely. Molting is not just a simple feather-shedding
phenomenon, it can cause severe strain to the penguins.  During the process of molting, the emperor
penguin refrain from eating, not only they fast, their usual walk in the cage
in a single line and occasionally swimming and other usual
activities are stopped. The shedding of feathers begins on the postero-ventral
portion of the body, and progresses in an irregular manner over the body of the
bird.

When breeding during the Antarctic winter, male emperor penguins fasts
about 115 days (pairing, egg brooding, beginning of feeding chicks with
esophageal secretion). Similarly, breeding females fast during 45 days from
pairing to egg laying. Moreover, both sexes fast for about 1 month during
summer molt. Natural starvation did not seem to self-induce marked changes in
plasma lipids (total lipids, triglycerides, phospholipids, total cholesterol),
but experimental forced fasting induced a drop-in plasma lipids, because of fat
store exhaustion. In males, plasma triglyceride was increased by 100% at the
time of copulation; all plasma lipids were minimum during mid-incubation, and
markedly increased at the time of egg hatching. In breeding females, plasma
total lipid and triglyceride increased tremendously and peaked at the time of
copulation, i.e., 10-15 days before laying. In molting birds, all plasma lipids
were depressed during feather synthesis and bypassed basal values at the end of
molt. Breeding (egg, esophageal secretion) and molting (new feathers)
productions, probably through endocrine influences, therefore markedly affect
plasma lipids in emperor penguins. (Rene Groscolas. (1982).

Emperor and other
penguins in general, shed their worn – out feathers and grow new ones each
year. The rigors of breeding and constant preening (straighten and clean
its feathers with its beak), subject a bird’s plumage to considerable wear and tear. Feather
must be replaced each year – usually after the nesting season. This process is
called molting. For many birds, molting happens slowly. It may even be hard to
notice that they are molting.

Molting
is a necessity for penguins, however, when they lose their feathers, they lose
their waterproof protection. They cannot go in the chilly water to feed until
new feathers have grown in. Before molting, penguins swim out to sea and eat as
much as they can. Then they wait. The old feathers start falling out in clumps.
Molting take place gradually over several weeks so that the bird retains
sufficient feathering to keep warm. However, penguins lose their waterproofing
so they must stay ashore until the molt is complete. During that time, the
penguins do not eat at all. By the time their new feathers have grown in, the
birds have lost half their body weight.

During
the year the feathers become badly worn by so much swimming and diving in the
salt sea water, by countless leaps ashore and back into the water, by sliding
games on the ice, by wind and sun, rain and snow. Before nest winter comes, the
plumage must be warm, thick and smooth again. So now, in summertime, the old
feathers fall out in bunches, and underneath, the spotless, shining new feather
suit is already growing. In this feather- growing period, which takes two to
three weeks, the “non – breeders’ simply stand around, doing nothing. They
cannot go out in search of food until their new coats are watertight, or they
would freeze to death in the icy water.

From
early November, chicks begin molting into juvenile plumage, which takes up to
two months and is often not completed by the time they leave the colony; adults
cease feeding them during this time. All birds make the considerably shorter
trek to the sea in December or January and spend the rest of the summer feeding
there. (Kooyman
GL et al, 1990).

Spontaneous
fasting during reproduction (sometimes with a full stomach) and molt is a major
characteristic of the annual cycle of penguins. Long-term fasting (up to four
months in male emperor penguins) is anticipated by the accumulation of fat
(incubation fast) and of fat and protein (molt fast). During most of the
incubation fast, birds rely almost entirely on lipids as an energy source, body
proteins being spared. (Groscolas R and Robin JP,  2001).

Increased oxygen storage is essential to the diving capacities
of marine mammals and seabirds. Myoglobin (Mb) and Mb mRNA concentrations were
analyzed in emperor penguin (Aptenodytes forsteri)
adults and chicks with spectrophotometric and RNase protection assays to
evaluate production of their large Mb-bound O2stores. Significant
Mb and Mb mRNA production occurred in chicks and young juveniles (Ponganis, P.J, et al, 2010).

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