Sphenisciformes (continued)
By this time, the sea ice has melted back close to the site of the
nesting colony.
Habitat
Penguins are found primarily in the cold southern oceans, on
the Antarctic continent and its surrounding islands, as well
as northward to Australia, New Zealand, South America, and
Africa. One species, comprising the Galápagos penguins
(Spheniscus mendiculus), is found in the Galápagos Islands,
which are on the Equator, but are surrounded by the cold
Humboldt Current.
Fossil record
The fossil record of the penguins begins in the late Eocene and
continues throughout the Tertiary. Fossils have been found
in Antarctica, Australia, and South Africa, approximating the
range of present-day penguins. The earliest fossil penguins
were already well specialized as flightless, wing-propelled
swimming birds, and their fossil history provides little new
information about the evolutionary history and distribution
of the group. Some fossil penguins were much larger than the
emperor penguin [which can reach 120 cm (48") in height and
is the largest living species]. Some Eocene species were gigan-
tic (possibly reaching 180 cm (72") in height] and had a long
spearlike bill.
Fig. 2: Adélie penguin (Pygoscelis
adeliae) incubating eggs. (Credit: iSTOCK )
Penguins are gregarious, breeding in large colonies along
coastal areas. The emperor penguin (Aptenodytes forsteri) also
breeds on ice packs along the Antarctic coasts during the fall.
The males and females, which are identical, form strong pair
bonds and share in the incubation and care of the downy
nestlings. The older young of some species are kept in large
groups, or crèches. Incubation of the one egg is the responsi-
bility of the male (Fig. 2), which remains on the nest for over
2 months in the winter without eating. The females leave the
breeding colony during this period to feed, and return fat and
laden with food for the young. Males then leave for the ocean
and return with food to relieve the females. This alternation
continues until the young are old enough to enter the water.
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