Rockhopper Penguins are among the smallest of the world’s penguins averaging 52 centimeters in length and 3 kilograms in weight. The word Penguin first appears in the 16th century as a synonym for the now extinct Great Auk. When European explorers discovered what are today known as Penguins in the Southern Hemisphere, they noticed their similar appearance to the Great Auk of the Northern Hemisphere and named them after this bird, although they are not closely related. Due to the harsh rocky environment, they cannot slide on their bellies like most penguins, so they hop to get from one place to another. Biologists left little ambiguity about this species’ preferred habitat when assigning its name. Rockhoppers are seen bounding rather than waddling among the craggy, windswept shorelines of the islands north of Antarctica, from Chile to New Zealand. Their distinct yellow stripe above each eye extends upward into a yellow crest on top of their head. Behind their head they have a black occipital (back of the head) crest. They have red eyes, short red-brown bulbous bills and pink feet and legs. Females are often slightly smaller than males. In spite of their small size, Rockhoppers are known to be quite aggressive. They are not intimidated by humans or by other birds and animals, even larger ones. Those incubating their eggs will peck at intruders that come too close. In spite of their fierce countenance with intruders however, Rockhoppers are very gentle with their partners and are often observed preening one another, a behavior known as allopreening. They prefer to nest among steep, rocky slopes that near the water’s edge. Breeding sites may be covered by grasses or shrubs, however older colonies typically include a worn path between the rocky breeding ground and the water. Breeding sites of Rockhopper Penguins are often close to sources of fresh water that this species is known to use for bathing and drinking.
The Rockhopper Penguin can dive up to 100 meters in depth, but typically dive in shallower waters. They often feed in groups. Rockhopper Penguins are opportunistic feeders and feed on crustaceans, squid and small fish. Rockhoppers often have enormous breeding colonies of up to 100,000 nests at a single site with nesting densities ranging from 1.5 to 3 nests per square meter. They often share colonies with nesting Albatrosses and Cormorants. Rockhopper Penguins return to the same breeding site each year and even use the same nest when possible, with minor touch ups with nesting material if necessary. Breeding begins in early October when males arrive at the breeding site a few days before females. Breeding takes place as soon as the females arrive and 2 eggs are laid 4-5 days apart in in early November. The first egg laid is typically smaller than the second (80 grams vs. 110 grams) and is the first to hatch. Incubation lasts about 33 days. The eggs are incubated by the parents as a pair for the first 10 days, then males leave to feed while the female incubates during the second shift. The male Rockhopper Penguin returns to take on the third shift and he generally remains for the duration of incubation and afterward to brood the chicks while the female leaves to forage and returns to feed the chicks. The chicks lack the yellow crest and red-brown bill of adult birds. When Rockhopper Penguin chicks begin to molt into adult plumage, sexually immature juveniles join the colony to molt. These young penguins can be distinguished from the newly fledged chicks by a faint yellow stripe above their eye the red-brown bill of adult Rockhoppers. Juveniles reach sexual maturity at about 4 years of age.