Rockhopper penguin

Taxonomy and classification

Rockhopper penguins were long treated as a single species, but modern studies of morphology, behavior and genetics have led most authorities to divide them into two or three taxa. There remains some disagreement among experts about how to rank these groups.

• Western rockhopper (Eudyptes chrysocome chrysocome)
• Eastern rockhopper (Eudyptes chrysocome filholi)
• Northern rockhopper (Eudyptes moseleyi)

Some researchers treat the western and eastern forms as subspecies of a single southern rockhopper, while others elevate all three to full species. These taxonomic differences reflect variation in plumage, vocalizations and breeding locations.

Appearance and behavior

Rockhoppers are relatively small penguins with sharply contrasting black-and-white plumage, pronounced yellow crest feathers over the eyes, and stout, orange to reddish bills. They walk awkwardly on land but compensate by hopping between rocks, keeping both feet together to spring upward — sometimes more than a metre — to clear boulders or reach nest sites. In the water they are agile and pursue prey with rapid wing-propelled dives.

Breeding, diet and life cycle

These penguins nest in dense colonies on rocky slopes and cliffs of subantarctic and temperate islands. Nests are shallow scrapes or cups lined with stones and vegetation. Pairs typically lay two eggs; the first-laid egg is often smaller and less likely to survive, a pattern known as brood reduction. Adults feed primarily on small schooling fish, krill, and squid, foraging close to shore during the breeding season and sometimes traveling farther in the nonbreeding months. Like other penguins, rockhoppers undergo a yearly moult during which they remain ashore and fast while replacing worn feathers.

Distribution and conservation

Rockhoppers occur on subantarctic islands and isolated oceanic islands in the southern Atlantic, Indian and Pacific Oceans — for example, colonies are known from the Falkland Islands, Tristan da Cunha group, Gough Island and several island groups in the southern Indian Ocean. Despite once being among the most numerous penguins, many rockhopper populations have declined sharply in the 20th and 21st centuries. Observed declines in some colonies have approached or exceeded large percentages of historical numbers.

• Primary threats include competition with commercial fisheries for prey, oil spills and other marine contamination, and introduced predators at breeding sites.
• Climate change may alter the distribution and abundance of their prey, further stressing populations.
• Human disturbance, egg collecting in the past, and disease have also affected some colonies.

Scientists link some of these pressures to overfishing and to marine contamination such as pollution, although the relative importance of different factors varies by island and colony. International conservation assessments list some rockhopper taxa at elevated risk of extinction, and local measures — protected breeding sites, fishing regulations and invasive predator control — are used to reduce threats.

Notable facts and distinctions

Rockhoppers are notable for their vivid head plumes and their noisy, braying calls in colonies. Their breeding strategy, which often yields one surviving chick from two eggs, is a well-studied example of parental investment and brood reduction in seabirds. Because the group shows regional differences in appearance and behavior, rockhoppers are an active subject of research into speciation, migration and the effects of changing ocean ecosystems.

Further reading and resources on rockhopper biology and conservation are available from specialist seabird organizations and regional conservation agencies. For general information about crested penguins see related resources on crested penguins, and for historical treatment of the group consult summaries that discuss their former status as a single species. The distinctive head feathers that give these birds their common name are often described simply as a crest, and are used in displays and identifications in the field.