The Macaroni penguin is one of six crested penguins with the identifying crest on its forehead, formed by long orange-yellow and black feathers, extending to the ear coverts on either side of the animal's head. The head, upper-parts, tail and upper flippers are black, while the under-parts are white. The animal has black chin and throat. The eyes are deep red and the beak is pinkish-red, consisting of horny plates. The webbed feet and short, sturdy legs of the animal are pink in color. Both males and females exhibit similar plumage while females are a bit smaller than males. Unlike adults, juvenile penguins have grey throat and chin. In addition, the crest on their head is shorter than that of adult individuals. Chicks have dark grey plumage, grey eyes, brownish-black beak, lacking the head crest.
These 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 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, the 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, the offshore islands of Australia and New Zealand.
These 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, these birds 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 animals, these birds 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, remaining emerged for 2 - 3 minutes, whereas during the night, they dive no deeper than 20 meters. Looking for feeding areas, Macaroni penguins can travel up to 400 km along the polar front. At the mating season, the birds typically fast for up to 40 days.
Macaroni penguins are carnivores. Their diet generally consists of krill, about 5% squid as well as small amount of fish and amphipod crustaceans.
Macaroni penguins have 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, 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 in 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, breeding population on Marion Island has sharply reduced due to disease outbreaks.
The overall population of this species is currently decreasing, being estimated to about 6.300.000 breeding pairs. On the IUCN Red List, the Macaroni Penguin is classified as Vulnerable (VU).