Rockhopper PenguinScientific name: Eudyptes chrysocome
Size: 2.5 kg (m), 2.4 kg (f)
Nest type: in colonies in the open; sometimes in association with other species
Favourite food: krill, fish and squid
Breeding in sometimes-large colonies throughout the sub-Antarctic. Smaller than its congeners, but no less aggressive. There is some evidence that the Northern Rockhopper or Moseley’s Penguin is deserving of separate species status. Whatever, the Northern Rockhopper and Southern Rockhopper are clearly closely related and much of what applies to one probably holds for the other, but actual data are still scarce.
Rockhoppers are distinguished from other crested penguins by their smaller size and by having only a thin yellow superscilium. The feather plumes are yellow, not orange as in Macaroni Penguin, and thinner than in the remaining Eudyptes species. The red eye is distinctive. Southern Rockhopper Penguins differ from their Northern counterparts in having a narrower supercilium and shorter plumes, which reach just over the black throat. Their vocalisations are also different. The Southern Rockhopper actually comprises two subspecies that have been described and can be identified in the field: the nominate form from South America and the Falkland Islands and the eastern subspecies filholi from the New Zealand sub-Antarctic islands. The eastern form mainly differs from the nominate subspecies in having a pink line of fleshy skin along the lower mandible which is black in the nominate subspecies. Immature birds have only a narrow supercilium and a pale mottled grey chin. Identification of juveniles is difficult. Shape of the supercilium, bill shape, body size and underwing pattern can aid identification. Separation of juvenile Southern and Northern Rockhopper Penguins in the field is probably impossible.
Breeding colonies are located on rocky slopes and amongst tussocks, sometimes in small caves and amongst crevices. A small nest is build from tussock, peat and pebbles. Nevertheless, most of the first-laid eggs (A-eggs) are lost during incubation. The few chicks that hatch from A-eggs almost invariably die during the first few days of brooding.
The northern form of the Rockhopper Penguin breeds in cool temperate climates, generally north of the subtropical convergence, with breeding occurring on Tristan da Cunha and Gough Island in the Atlantic Ocean and St. Paul and Amsterdam Islands in the Indian Ocean. The breeding season starts three months earlier (July) than in the southern form. The latter is restricted to the northern sub-Antarctic and has a circumpolar distribution. Breeding colonies are around the Cape Horn area, Falklands, Prince Edward, Marion, Crozet, Kerguelen, Heard, Macquarie, Campbell, Auckland and Antipodes Islands. Campbell Island used to be the eastern stronghold of the species, but the population there has plummeted recently.
Migration and Vagrancy:
The non-breeding pelagic range is poorly known. Moulting birds especially have been found in South Africa, Australia and New Zealand. The western subspecies (nominate form) has been recorded as far as the Snares Islands during moult. Vagrants of the Northern Rockhopper have been recorded on the Chatham Islands.
Crustaceans, in particular euphausids, make up the bulk of food items consumed during most studies of this species. Fish and cephalopods play a minor role, though one study found 53% cephalopods (by weight). Over 90% of the diet (by mass) of Northern Rockhopper Penguins breeding on Gough Island consisted of crustaceans (mainly euphausids). The remaining 10% was made up of fish and, to a very small extent, squid.