Crested penguin

The term crested penguin is the name given to several species of penguin of the genus Eudyptes. The exact number varies between four and seven depending on the authority, and a Chatham Islands species may have become extinct in the 19th century. All are black and white penguins with yellow crests and red bills and eyes, and are found on subantarctic islands in the worlds southern oceans. All lay two eggs but raise only one young per breeding season; the first egg laid is substantially smaller than the second.

Taxonomy
The genus was described by the French ornithologist Louis Jean Pierre Vieillot in 1816; the name is derived from the Ancient Greek words eu "good", and dyptes "diver".

Six extant species have been classically recognised, with the recent splitting of the Rockhopper Penguin increasing it to seven. Conversely, the close relationship of the Macaroni and Royal Penguins, and the Erect-crested and Snares Penguins have led some to propose the two pairs should be regarded as species. ORDER SPHENISCIFORMES The Chatham Islands form is known only from subfossil bones, but may have become extinct as recently as the late 19th century as a bird kept captive at some time between 1867 and 1872 might refer to this taxon. It appears to have been a distinct species, with a thin, slim and low bill.
 * Family Spheniscidae
 * Fiordland Penguin, Eudyptes pachyrhynchus
 * Snares Penguin, Eudyptes robustus – has been considered a subspecies of the Fiordland Penguin.
 * Erect-crested Penguin, Eudyptes sclateri
 * Southern Rockhopper Penguin, Eudyptes chrysocome
 * Eastern Rockhopper Penguin, Eudyptes (chrysocome) filholi
 * Western Rockhopper Penguin, Eudyptes (chrysocome) chrysocome
 * Northern Rockhopper Penguin, Eudyptes moseleyi – traditionally considered a subspecies of Eudyptes chrysocome as the Rockhopper Penguin.
 * Royal Penguin, Eudyptes schlegeli – sometimes considered a morph of E. chrysolophus
 * Macaroni Penguin, Eudyptes chrysolophus
 * Chatham Penguin, Eudyptes chathamensis. (prehistoric?)

Evolution
Mitochondrial and nuclear DNA evidence suggests the Crested Penguins split from ancestors of their closest relative, the Yellow-eyed Penguin, around 15 million years ago, before splitting into separate species around 8 million years ago.

Description
The crested penguins are similar in appearance, having sharply delineated black and white plumage with red beaks and prominent yellow crests. Their calls are more complex than those of other species, with several phrases of differing lengths. The Royal Penguin (mostly) has a white face, while other species have black faces.

Breeding
Crested penguins breed on subantarctic islands in the southern reaches of the world's oceans; the greatest diversity occurring around New Zealand and surrounding islands. Their breeding displays and behaviours are generally more complex than other penguin species. Both male and female parents take shifts incubating eggs and young.

Crested penguins lay two eggs but almost always raise only one young successfully. All species exhibit the odd phenomenon of egg-size dimorphism in breeding; the first egg (or A-egg) laid is substantially smaller than the second egg (B-egg). This is most extreme in the Macaroni Penguin, where the first egg averages only 60% the size of the second. The reason for this is a mystery, although several theories have been proposed, remains unknown. British ornithologist David Lack theorized the genus was evolving toward the laying of a one-egg clutch. Experiments with egg substitution have shown that A-eggs can produce viable chicks which were only 7% lighter at time of fledging.

Recently, brooding Royal and Erect-crested Penguins have been reported to tip the smaller eggs out as the second is laid.

Species photographs
Photographs of adults of the extant (living) species are shown: