These birds are the smallest yellow-crested penguins. The Rockhopper penguin has yellow crest on its head, consisting of two separate parts and made up of long, thin, yellow feathers, forming eyebrows that stretch behind each eye of the animal. The crest is black on the back of the head. The head, neck, tail, flippers and the upper parts are black, whereas the under parts are white. The legs are short and the feet are webbed, colored in pale pink and equipped with black claws. The underside of their flippers is white and fringed with black. The Rockhopper penguins have red eyes. The beak is thick, colored in pinkish-red to reddish-horn. Chicks of this species are identified by grey head and upper parts and white under parts. Juveniles, on the other hand, exhibit duller bare parts and shorter crest, compared to that of adult penguins. Both sexes look alike, though males are noticeably larger than females, having thicker beaks.
Although the area of their distribution depends on species, these birds are usually found in the sub-Antarctic as well as parts of the southern Indian and Pacific Oceans. Breeding areas of the Northern rockhoppers are Amsterdam and St Paul Islands, and islands of Tristan da Cunha. Southern rockhoppers occur at the tip of the South America, breeding in Pacific Ocean and on sub-Antarctic islands of the Indian Ocean. These penguins live on rocky shorelines, nesting and constructing their burrows in tall grasses known as tussocks.
These penguins are highly sociable animals, nearly always seen in colonies. In fact, the rockhopper penguin is the most aggressive and most numerous penguin species in the world. By the end of the summer to the beginning of the autumn, the penguins leave their breeding colonies, going out to sea, where they live and feed for 3 - 5 months. Rockhopper penguins are diurnal animals. When on land, they move by jumping over rocks, boulders and rocky cracks instead of sliding on their belly, as most penguins do. When resting, these animals usually hide their head under their wing. When the penguin shakes its head, the yellow crest takes shape of a “halo”, which attracts mates. These birds use various forms of communication, including head shaking, head and flippers weaving, bowing, gesturing and preening.
Rockhopper penguins are carnivorous. The diet of these penguins primarily consists of fish, octopus, cuttlefish, krill, squid, mollusks, planktons as well as crustaceans.
Rockhopper penguins have monogamous mating system, forming lifelong pairs. Mating season occurs in the beginning of spring or by the end of summer. Every year, they return to the same nesting grounds. Their nests are holes, scratched in the ground and defined by dried grasses. Two eggs are laid and incubated for 32 - 34 days by both parents, which take turns every 7 - 17 days. As a general rule, the male is responsible for rearing the chicks, whereas the female forages to provide the offspring with food. By 3 weeks old, the hatchling joins a crèche of other chicks, where it finds protection. Reaching the age of 65 - 72 days, the chick molts, leaving the nest and going out to sea.
One of the serious concerns, threatening the population of these birds is human: people occasionally hunt the Rockhopper penguins and collect their eggs, which is particularly common in southern Chile. Commercial fisheries significantly decrease the amount of prey items throughout the area of their range. In addition, these animals presently suffer from oil spills. On the other hand, the animals are exposed to environmental changes, which negatively affect the productivity among these penguins and reduce numbers of prey in their main foraging areas. In fact, climate change is considered to be the primary reason of a sharp decline of their population on the Falkland Islands.
The exact number of these penguins’ population is presently unknown though decreasing. The population of Southern rockhopper is considered to be more than 1.5 million breeding pairs, being classified as Vulnerable on the IUCN Red List; Northern rockhoppers are estimated at approximately 240,300 pairs, and are listed as Endangered species.