New Zealand is significant in the evolution of crested penguins – four of the world's eight species breed there, three exclusively. A fifth species, the royal penguin, Eudyptes schlegeli, breeds on nearby Macquarie Island. Macquarie Island is in the same geographic group as New Zealand's subantarctic islands, but is administered by Australia.
Crested penguins are distinguished by crests of yellow feathers above the eyes that look like unruly eyebrows. The length and shape of the crest is peculiar to each species.
Two eggs, one chick
These penguins present one of biology’s great unsolved mysteries. They are known as obligate brood reducers – they lay two eggs but only fledge a single chick. Furthermore, the second egg is much bigger than the first, and it is usually from this that the successful chick hatches.
Tracking the penguins with satellites and global positioning systems reveals that they forage offshore, tens and even hundreds of kilometres from the colony. It may require too much energy to transport food for two chicks over such a distance – which could explain why the adults rear only one chick, but not why they lay two eggs.
Fiordland crested penguins
The Fiordland crested penguin or tawaki (Eudyptes pachyrhynchus) is found around the south-western coast of the South Island, Stewart Island and associated offshore islands. Fossil remains show that this species once occurred around the South Island and probably also on the North Island, so some call it the New Zealand crested penguin.
Around 67 centimetres long and weighing about 4 kilograms, they nest in dense rainforest. They eat squid, fish and crustaceans, feeding on the narrow continental shelf out from the western coast during breeding.
Snares crested penguins
This species (Eudyptes robustus) is restricted to the tiny Snares island group. A slightly larger version of the Fiordland crested penguin, at about 65 centimetres and 3 kilograms, it is distinguished by a fleshy margin at the base of its bill.
The erect-crested penguin (Eudyptes sclateri) is largely restricted to the Antipodes Islands and Bounty Islands, with a few isolated pairs breeding on the Auckland Islands. A relatively solid medium-sized penguin at 5.4–6.4 kilograms and 68 centimetres, its crest of yellow plumes is strikingly upright when dry on land.
The eastern rockhopper penguin (Eudyptes filholi) breeds on islands in the subantarctic Pacific and Indian oceans, and the related western rockhopper penguin (Eudyptes chrysocome) on islands in the subantarctic Atlantic Ocean and around Cape Horn. They are the smallest of the crested penguins, at 61 centimetres and 2.5 kilograms. The slightly larger Moseley's rockhopper penguin (Eudyptes moseleyi) breeds further north on islands in the South Atlantic and Indian oceans. Within New Zealand, eastern rockhopper penguins breed on the subantarctic Campbell, Auckland and Antipodes island groups.