Difference between revisions of "Adélie penguin"

The '''Adélie penguin''' (''Pygoscelis adeliae'') is a species of [[penguin]] common along the entire [[Antarctica|Antarctic]] coast, which is their only residence. They are among the most southerly distributed of all seabirds, along with the [[emperor penguin]], the south polar skua, [[Wilson's storm petrel]], the [[snow petrel]], and the [[Antarctic petrel]]. They are named after [[Adélie Land[[, in turn named for Adèle Dumont D'Urville, the wife of French explorer Jules Dumont d'Urville, who discovered these penguins in 1840.

Based on a 2014 analysis of fresh guano-discolored coastal areas, 3.79 million breeding pairs of Adélie penguins are in 251 breeding colonies, a 53% increase over a census completed 20 years earlier. The colonies are distributed around the coastline of the Antarctic land and ocean. Colonies have declined on the [[Antarctic Peninsula]], but those declines have been more than offset by increases in East Antarctica. During the breeding season, they congregate in large breeding colonies, some over a quarter of a million pairs. Individual colonies can vary dramatically in size, and some may be particularly vulnerable to climate fluctuations. The Danger Islands have been identified as an "important bird area" by BirdLife International largely because it supports Adélie penguin colonies, with 751,527 pairs recorded in at least five distinct colonies. In March 2018, a colony of 1.5 million was discovered.

Adélie penguins breed from October to February on shores around the Antarctic continent. Adélies build rough nests of stones. Two eggs are laid; these are incubated for 32 to 34 days by the parents taking turns (shifts typically last for 12 days). The chicks remain in the nest for 22 days before joining crèches. The chicks moult into their juvenile plumage and go out to sea after 50 to 60 days.

Adélie penguins are preyed on by [[leopard seals]], [[skuas]], and occasionally, [[orca|killer whales]].

Specifics of their behaviour were documented extensively by Apsley Cherry-Garrard (a survivor of [[Robert Falcon Scott]]’s fateful final journey to the [[South Pole]]) in his book The Worst Journey in the World. Cherry-Garrard noted: "They are extraordinarily like children, these little people of the Antarctic world, either like children or like old men, full of their own importance." Certain displays of their selfishness were commented upon by George Murray Levick, a Royal Navy surgeon-lieutenant and scientist who also accompanied Scott on his ill-fated British Antarctic Expedition of 1910, during his surveying of penguins in the Antarctic:

<blockquote>"At the place where they most often went in [the water], a long terrace of ice about six feet in height ran for some hundreds of yards along the edge of the water, and here, just as on the sea-ice, crowds would stand near the brink. When they had succeeded in pushing one of their number over, all would crane their necks over the edge, and when they saw the pioneer safe in the water, the rest followed."</blockquote>

Regularly, this attitude led to the demise of an Adélie penguin, "Then the final fatal steps forward are taken and they come within reach. There is a spring, a squawk, a horrid red patch on the snow, and the incident is closed."[15] Others on the mission to the South Pole were more receptive of this element of the Adélies' intrigue. Cherry-Garrard:

The Adélie penguin is known to feed mainly on Antarctic krill, ice krill, [[Antarctic silverfish]], sea krill, and glacial squid (diet varies depending on geographic location) during the chick-rearing season. The stable isotope record of fossil eggshell accumulated in colonies over the last 38,000 years reveals a sudden change from a fish-based diet to [[krill]] that started 200 years ago. This is most likely due to the decline of the [[Antarctic fur seal]] since the late 18th century and baleen whales in the 20th century. The reduction of competition from these predators has resulted in a surplus of krill, which the penguins now exploit as an easier source of food.

Adélie penguins arrive at their breeding grounds in October or November, at the end of winter and the start of spring. Their nests consist of stones piled together. In December, the warmest month in Antarctica (about −2 °C or 28 °F), the parents take turns incubating the egg; one goes to feed and the other stays to warm the egg. The parent that is incubating does not eat. In March, the adults and their young return to the sea. The Adélie penguin lives on sea ice, but needs the ice-free land to breed. With a reduction in sea ice, populations of the Adélie penguin have dropped by 65% over the past 25 years in the [[Antarctic Peninsula]].

Young Adélie penguins which have no experience in social interaction may react to false cues when the penguins gather to breed. They may, for instance, attempt to mate with other males, with young chicks, or with dead females. On account of the birds' relatively human-like appearance and behavior, human observers have interpreted this behavior anthropomorphically as sexual deviance. The first to record such behavior was Dr Levick, in 1911 and 1912, but his notes were deemed too indecent for publication at the time; they were rediscovered and published in 2012.

"The pamphlet, declined for publication with the official Scott expedition reports, commented on the frequency of sexual activity, auto-erotic behaviour, and seemingly aberrant behaviour of young unpaired males and females, including necrophilia, sexual coercion, sexual and physical abuse of chicks and homosexual behaviour," states the analysis written by Douglas Russell and colleagues William Sladen and David Ainley. "His observations were, however, accurate, valid and, with the benefit of hindsight, deserving of publication." Levick observed the Adélie penguins at Cape Adare, the site of the largest Adélie [[penguin rookery]] in the world. As of June 2012, he has been the only one to study this particular colony and he observed it for an entire breeding cycle. The discovery significantly illuminates the behavior of the species that some researchers believe to be an indicator of [[climate change]].

Adélie penguins living in the Ross Sea region in Antarctica migrate an average of about 13,000 kilometers (8,100 mi) during the year as they follow the sun from their breeding colonies to winter foraging grounds and back again. "Follow the sun" means that during the winter the sun does not rise south of the [[Antarctic Circle]], but sea ice grows during the winter months and increases for hundreds of miles from the shoreline, and into more northern latitudes, all around Antarctica, so that as long as the penguins live at the edge of the fast ice, there will be sunlight. As the ice recedes in the spring, they remain on the edge of it, until they are once again on the shoreline during a sunnier season. The longest treks have been recorded at 17,600 kilometers (10,900 mi).