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PENGUIN,
common name for flightless, aquatic birds of the southern
hemisphere, constituting the order Sphenisciformes. The name penguin
originally was applied to the now extinct great auk of the North
Atlantic, a large flightless, black and white bird with an upright
stance. Similar flightless birds were discovered subsequently in
the southern hemisphere, and they were also called penguins, a name
that is now restricted exclusively to these birds.
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Most penguins have a white breast and a black back and head.
Several species exhibit red, orange, or yellow patches on the head
and neck. Because their short legs are placed far back on their
bodies, penguins assume an upright posture.
Penguins are grouped into 18 species and 6 genera, most of
which are found in Antarctica and on subantarctic islands. Others
are native to the coasts of Australia, South Africa, and South America,
and the Galápagos Islands.
The largest species are the king penguin, Aptenodytes
patagonica, from 91 to 97 cm (36 to 38 in) in height, and
the emperor penguin, A. forsteri, which may attain
a height of more than 120 cm (48 in). Both species of the Aptenodytes genus
are found on the Antarctic ice barrier. The king penguin is also
found in Tierra del Fuego and on eight islands in the southern hemisphere.
The smallest penguin is the little blue penguin, Eudyptula
minor, of Australia and New Zealand; its height is 41 cm
(16 in) or less. Unlike most species, the king, emperor, and little
penguins have blue-gray backs. Another distinguishing feature of
the king and emperor penguins is the presence of bright reddish
or pinkish shields on the sides of their mandibles and large orange
or yellow patches on the sides of their necks.
The yellow-eyed penguin, Megadyptes antipodes, and
the 6 species of the genus Eudyptes have yellowish
feather crests on the sides of their heads. Members of the Eudyptes genus
inhabit the Antarctic waters south of New Zealand and Tasmania and
range northward along the east coast of South America and to Tristan
da Cunha, an island in the South Atlantic. The gentoo penguin, Pygoscelis
papua, and the Adélie penguin, P. adeliae, are
representative of the genus found in Antarctica and in the South
Shetland, South Orkney, and South Sandwich islands. The jackass
penguin, Spheniscus demersus, is found off the
coasts of South Africa. The cold Humboldt Current along the west
side of South America permits two species to breed in what are otherwise
tropical latitudes: the Galápagos penguin, S. mendiculus, on
the Galápagos Islands and the Humboldt penguin, S.
humboldti, on the South American coast and offshore islets.
Although descended from flying ancestors, penguins have become
highly specialized for swimming; their stiffly held wings resemble
the paddles of other swimming vertebrates. Penguins do not have
specific feather tracts, as do most birds, but are covered almost
uniformly with small, scalelike feathers. Whereas most birds shed
their feathers and grow new ones during a relatively long period
of the year, penguins molt all of their feathers and, in some species,
even shed the shields from the beak within a short space of time.
A molting penguin has a swollen, disheveled appearance; it loses
its feathers in huge patches as new feathers appear. During the
molting period, which may last several weeks, the penguin does not
enter the water to feed.
The ability to withstand intense cold is one of the penguin’s
greatest assets. Most penguins have rather small feet, wings, and
heads; the relatively little surface area in comparison to the bird’s
volume results in excellent heat conservation. In addition, many
penguins have a thick insulating layer of fat under the skin. Some
species are better equipped for cold weather than others. The emperor
penguin, which may weigh 27 to 32 kg (60 to 70 lb), appears to be
the best equipped of all.
Penguins usually walk or hop and toboggan along on their breasts,
pushing with wings and feet. They swim with great speed and agility.
The flippers are their sole means of propulsion; the feet are trailed
behind or used in steering. Some species progress by porpoising,
which is swimming underwater some distance, emerging in a graceful
arc to take a fresh breath, and submerging again. Penguins feed
on fish, cuttlefish, crustaceans, and other small sea animals. In
captivity the king and emperor penguins normally do not learn to
pick up their own food, and after they have been taught to feed
by strenuous forced feeding they must be fed by hand each day.
Penguins are gregarious birds and are found in flocks even
at sea. On land the colonies often number in the hundreds of thousands.
Although the birds have suffered greatly at the hands of humans,
who have slaughtered great numbers for their blubber and, more recently,
for their skins, the inaccessibility of the Antarctic region has
helped preserve the group. Natural enemies of the penguin include
leopard seals, killer whales, and, in the case of young chicks and
eggs, skuas.
The greatest concentrations of penguins are seen in rookeries
where the birds gather to breed. Several species of penguin may
be found nesting in a single rookery, but usually the species are
well segregated. At the mating season the penguins of the Antarctic
region appear along desolate, ice-bound, or rocky coasts and hop,
jump, waddle, and toboggan toward favored breeding sites. In many
of these areas smooth paths have been worn over hard rock formations
by countless generations; the birds use precisely the same paths
as their antecedents to approach the rookery. Often the paths seem
to be the most circuitous and difficult routes to the rookery, and
in some cases the sites are located many kilometers from the ocean.
More northern species may be resident in the area of the rookery.
The emperor penguin breeds in one of the world’s most inhospitable
regions during one of the coldest periods of the year, laying and
incubating its eggs in temperatures as low as −62° C
(–80° F).
Penguins indulge in strange postural displays and calls in
the process of finding mates within their own species. The gentoo
penguin raises its flippers and calls or bows in a manner peculiar
to the gentoo; the jackass penguin bows, shakes his head, and brays
in a characteristic jackasslike call; and the courtship display and
clear trumpeting of the king penguin are specific to that species;
members of the genus Spheniscus, which do not meet
in the wild, will readily hybridize in zoos.
Penguins vary in their nesting methods, and some species build
no nests at all. The Humboldt and jackass penguins prefer a sheltered
retreat, such as a burrow, and utilize sticks and other debris to
form the nest. Others, such as the Adélies, incubate their
eggs in the open on nests formed of stones or sticks. King and emperor
penguins build no nests; in these species the bird holds its single
egg in the top of its feet, hunching down over it so that a fold
of abdominal skin covers and warms the egg.
Most species of penguin lay a clutch of two eggs, which are
white or greenish in color. Incubation periods vary according to
species. King penguin eggs require more than 50 days of incubation
before hatching, whereas jackass eggs hatch in 32 to 36 days.
In general, both sexes incubate the eggs and feed the young. The
male Adélie penguin usually incubates the eggs for the
first two weeks, fasting, while the female returns to the sea to
feed and bathe. The male has been known to fast during the entire
time that the nesting territory is established and defended, courtship
takes place, and the eggs are laid and incubated. When the female takes
its turn at the brooding, the male goes to the distant sea to feed
and, within an amazingly short period, restores its reservoir of
fat and returns to the rookery with food for the young soon due
to hatch. Both parents share responsibility for feeding the young
penguins. Not all species of penguin undergo such strenuous fast periods
during the breeding period as do the Adélies; many nest
in areas where the birds can make several trips daily to the sea
for food.
Most penguin chicks are covered with a sooty-gray down at
hatching, although some have a pattern of soft grays and whites.
Chicks of certain species remain confined to the burrow or nest
through the entire nesting period, during which they are fed by
their parents. Among other species the chicks, after reaching a stage
of development in which they do not require constant care from the
parents, are grouped in areas called nurseries. There they wait
until the parents hunt for food. On their parents’ return
parents and chicks recognize each other in a group often numbering
thousands. In some cases there ensues a feeding chase in which the
chick leaves the nursery to chase one of its food-laden parents.
The parent finally stops and regurgitates partially digested food
for the chick. After a young penguin has shed the last of its down
and acquires its first plumage, it enters the sea to fend for itself.