We all know that penguins are flightless, aquatic birds; and they are mostly found in the southern hemisphere, especially the Antarctic Islands. Even though their taxonomical classification is still a much-debated topic; as of date, there are around 17 to 20 species of extant (existing) penguins that are divided into six genera, and all of them belong to the family Spheniscidae. The members of the genus Eudyptes are characterized by an ornamental tuft on their heads, and hence they are called crested penguins. Rockhopper penguins belong to this genus, and are so named due to their hopping habit. They hop between rocks, with their feet held together. Interesting Facts So, rockhoppers belong to the genus Eudyptes in the family Spheniscidae. They are one among the crested penguin species, with an ornamental tuft on their heads. In fact, they are the smallest among the crested penguins. Earlier, these penguins were classified as a single species (Eudyptes chrysocome); but now, they are divided into three different species that are closely related. They include the western rockhopper penguin (Eudyptes (chrysocome) chrysocome), eastern rockhopper penguin (Eudyptes (chrysocome) filholi) and northern rockhopper penguin (Eudyptes moseleyi). Even though, rockhopper penguins are now classified into three different species, they share similar characteristics, which are listed below.

• Being a crested penguin, the rockhopper has yellow tufts above the eyes, a red-colored beak, and a black and white plumage. Their eyes are also blood red in color.
• The tuft on the head of rockhopper penguins have spiky yellow and black feathers. The yellow spiky feathers that look like eyebrows, project on either side of the head. They have black spiky feathers on top of their head.
• The top of the head, the back, and the flippers are covered with bluish black plumage; and the rest of the body is white. Their feet are pink and webbed. Rockhopper penguins too molt and lose the feathers during some seasons.
• Being the smallest crested penguins, rockhoppers have a height of around 45 to 60 centimeters, and a body weight of two to three kilograms. A rockhopper penguin has a big head, short and thick neck, a wedge-shaped tail, and strong flippers. The body of this penguin has a streamlined shape.
• These penguins are sub-Antarctic species that are mainly found in and around the Antarctica. They are found in regions, like Macquarie Island of Australia, Campbell Island (Newzealand), Falklands, Antipodes, and Tristan da Cunha. Rockhopper penguin habitat includes grasses on the rocky coastlines of these regions.
• Unlike other penguin species, rockhoppers are aggressive and bad-tempered. They are found to fight for food, territory, nesting materials, and mating partners. They make loud noises, especially during the breeding season. Usually, these penguins feed on krill, squid and small fish. In case of scarcity of food, they may consume anything that is found in water.
• These penguins attract their mates with loud cries and other complex behavior. Apart from these noises, their communication involves lots of actions, like shaking head and moving flippers.
• Mating of rockhopper penguins takes place during the summers. The mating partners dig a hole in the ground and line it with dried grass. The female lays two eggs, one smaller than the other. Only the bigger egg hatches, and the incubation time is around 35 days.
• Once hatched, the young one is guarded by both the male as well as the female. It has been observed that the males are capable of regurgitating milk from their digestive systems, so as to feed the offspring, when the female is away. This feature is found in certain other penguin species too.

These interesting aquatic birds have a lifespan of around 10 years. Even though they are found in large numbers, rockhopper penguin population is now facing decline. They are now declared 'vulnerable', by the IUCN. Rising pollution levels and predator attacks are cited as the main reasons for their dwindling population.