The Adélie penguin (Pygoscelis adeliae) is a species of penguin common along the entire coast of the Antarctic continent. This is the only place where it is found. It is the most widespread penguin species, and, along with the Emperor penguin, is the most southerly distributed of all penguins. It is named after Adélie Land, in turn, named for Adèle Dumont d'Urville, who was married to French explorer Jules Dumont d'Urville, who first discovered this penguin in 1840.
Adélie penguins of both sexes look the same but females have shorter wings and beaks and weigh significantly less. Adult birds are black on the head, throat, and upper parts, with snowy white underparts. They have a conspicuous white eye ring around a black iris. The beak is largely covered with black feathers, leaving only the tip exposed; this is primarily black, though it can show indistinct reddish-brown markings. The upper surface of the wing is black with a white trailing edge, while the underside is white with a narrow black leading edge and a small black tip. The legs and feet, which are mostly unfeathered, are pinkish. Upon hatching, the chick is fully covered in down feathers. This coat of feathers is typically silvery-grey (darker on the head), though some birds are much darker overall. Within 10 days, the chick molts into another set of down feathers, this time all dark smoky grey. Once they have molted a third time, 7-9 weeks after hatching, the immature birds are similar to adults in appearance, though they tend to be smaller with a bluer tinge to their upperparts and white (rather than black) chins and throats. They lack the full white eye ring of the adult until they are at least a year old.
The Antarctic region is the only place, where these amazing birds live. Typically, they inhabit rocky beaches along the coastline of Antarctica and offshore islands, preferring areas that are free of ice. However, the highest concentration of these penguins is in the Ross Sea.
Adélie penguins are diurnal birds. They are highly social and communicative animals, gathering into small colonies, where they live, socialize, forage, hunt as well as find protection from predators. When it comes to nesting, these penguins usually display extremely territorial behavior, sometimes even stealing nesting sites from each other. Adélie penguins are migratory animals. Thus, in the winter, the penguin colonies are usually found in coastal areas, on large ice platforms. Then, with the approaching of the breeding season (at the beginning of spring and during summer months), the penguins migrate to the seashore, looking for ice-free areas, where they construct their nests.
Adélie penguins are carnivores (piscivores and molluscivore). Their diet primarily consists of krill. They will also consume other aquatic species, including silverfish, squid as well as crustaceans.
Adélie penguins form monogamous pairs, remaining together throughout their lives. During October-November, the birds travel to their breeding grounds, constructing nests from stones and loose pieces of grass. Typically, the female lays 2 eggs at an interval of 2 days, after which both parents incubate the eggs for around 36 days. During the incubation period, the parents usually go out to sea to forage, leaving the nest one by one and taking turns with the eggs. Then, when the chicks are hatched, they again take turns to forage and feed the hatchlings, which are born semi-precocial and are not able to feed themselves. The hatchlings are born with their down feathers. By the age of 4 weeks, they join a creche or group of other chicks, where they find protection. However, during this period the parents still continue feeding the chicks for about 56 days, after which the young are independent.
Industrial fishing is among the notable threats to the species, reducing the numbers of fish and krill populations and causing food shortages in some areas of their range. However, the primary threat is environmental changes: populations in the northernmost part of their range are exposed to air and water warming, which reduces the area of sea ice, destructing their habitat. If the temperature continues increasing throughout the Antarctic, it will eventually lead to a serious danger to the Adélie penguin populations.
According to IUCN Red List, the total population size of the Adélie penguin is 7,580,000 mature individuals. Currently, this species is classified as Least Concern (LC) on the IUCN Red List, and its numbers today are increasing.
Feeding upon krill and Antarctic silverfish, Adélie penguins thus control their numbers.
