The Macaroni penguin (Eudyptes chrysolophus) is a species of penguin found from the Subantarctic to the Antarctic Peninsula. It is very closely related to the Royal penguin, and some authorities consider the two to be a single species. Numbering up to 100,000 individuals, the breeding colonies of the Macaroni penguin are among the largest and densest of all penguin species. After spending the summer breeding, they disperse into the oceans for six months.
The head, chin, throat, and upper parts of the Macaroni penguin are black and sharply demarcated against the white under parts. The black plumage has a bluish sheen when new and brownish when old. The most striking feature is the yellow crest that arises from a patch on the center of the forehead and extends horizontally backward to the nape. The flippers are blue-black on the upper surface with a white trailing edge and mainly white underneath with a black tip and leading edge. The large, bulbous bill is orange-brown. The iris is red and a patch of pinkish bare skin is found from the base of the bill to the eye. The legs and feet are pink. The males and females are similar in appearance; males tend to be slightly larger. Males also bear relatively larger bills, which average around 6.1 cm (2.4 in) compared to 5.4 cm (2.1 in) in females; this feature has been used to tell the sexes apart. Immature birds are distinguished by their smaller size, smaller, duller-brown bill, dark grey chin and throat, and absent or underdeveloped head plumes, often just a scattering of yellow feathers. The crest is fully developed in birds aged three to four years, a year or two before breeding age.
Macaroni penguins inhabit rocky and water-bound terrains, being found on cliffs and rocks. In South America, their range stretches from southern Chile to the Falkland Islands, South Georgia, the South Sandwich Islands, and the South Orkney Islands. The Macaroni penguins are widely distributed across Antarctica, the Sub Antarctic, and the Antarctic Peninsula, found on the northern South Shetland Islands, Bouvet Island, Prince Edward and Marion Islands, the Crozet Islands, the Kerguelen Islands, and the Heard and McDonald Islands. They also make long-distance foraging trips, reaching as far as southern Brazil, Tristan da Cunha, South Africa, and the offshore islands of Australia, and New Zealand.
Macaroni penguins are highly social animals, gathering into large colonies, which generally consist of breeding pairs and contain up to 2.5 million individuals. When on land, they are extremely noisy, giving out harsh braying sounds; when at sea, they tend to bark. They communicate with each other through ritual behavior, accompanying their calls by moving, waving their heads and flippers, bowing, and preening. Being both diurnal and crepuscular, Macaroni penguins are active throughout the day. They forage by day, often remaining in water from dawn to dusk. During the daytime hours, they can dive at a depth of 20-80 meters (65-262 ft), remaining emerged for 2-3 minutes, whereas during the night, they dive no deeper than 20 meters (65 ft). Macaroni penguins molt once a year, a process in which they replace all of their old feathers. They spend around two weeks accumulating fat before molting because they do not feed during the molt, as they cannot enter the water to forage for food without feathers. The process typically takes 3-4 weeks, which they spend sitting ashore. Once finished, they go back to sea and return to their colonies to mate in the spring.
Macaroni penguins are carnivores (piscivores). Their diet generally consists of krill, about 5% squid as well as a small amount of fish and amphipod crustaceans.
Macaroni penguins have a monogamous mating system, forming lifelong pairs. During the breeding season, they gather into large colonies. Usually, males arrive before females to establish territories. The female lays two eggs, the first of which is smaller and is not incubated. The eggs are typically laid in a shallow scrape, made in the ground. The second, larger egg is incubated by both parents for about 34 days. For the first 3-4 weeks after hatching, the male remains with the chick, caring for the hatchling, whereas the female forages to provide them both with food. After a while, the hatchling joins a crèche of other young penguins while both parents forage to feed the chick. By the age of 10 weeks, the youngster attains its adult plumage and can go out to sea.
One of the major threats is overfishing, which considerably reduces populations of krill and other small invertebrates that are the main source of food for these penguins. At their breeding grounds, the birds are exposed to oil pollution, fishing, and global warming. On the other hand, the breeding population on Marion Island has sharply reduced due to disease outbreaks.
According to IUCN Red List, the total population size of the Macaroni penguin is 6.3 million breeding pairs. Currently, this species is classified as Vulnerable (VU) on the IUCN Red List, and its numbers today are decreasing.