The Snares penguin (Eudyptes robustus; ), also known as the Snares crested penguin and the Snares Islands penguin, is a penguin from New Zealand. The species breeds on the Snares Islands, a group of islands off the southern coast of the South Island. It is a yellow-crested penguin, with a size of and a weight of . It has dark blue-black upper parts and white underparts. It has a bright yellow eyebrow-stripe which extends over the eye to form a drooping, bushy crest. It has bare pink skin at the base of its large red-brown bill.
The species nests in colonies ranging in size from around 10 nests to around 1200, under forest cover or the open. The main colonies are located on North East Island; other colonies are established on Broughton Island as well as the rocky Western Chain.
The Snares penguin's main prey is krill, supplemented by squid and small fish. The species is rated as vulnerable by the International Union for Conservation of Nature (IUCN) as its breeding range is restricted to one small island group. The population is estimated at around 25,000 breeding pairs.
Taxonomy
Snares penguins were originally collected in 1874 and named atrata by Frederick Hutton. However, Hutton lost his sample at sea whilst drawing the bird before a full speciation could be identified. A description written by Hutton and an illustration done by Keulemans in Buller's A History of the Birds of New Zealand are evidence that this is the same penguin previously identified by Hutton.
However, there is some debate over the classification of this penguin, and Oliver was able to successfully propose that a few slight anatomical differences did exist between the Snares penguins and the early description and illustration, leading the Snares penguin to be called robustus instead of atratus.
Distribution and habitat
The Snares penguin is named after the place in which it breeds
—the Snares Islands. The Snares Islands are a small group of islands off the coast of southern New Zealand. Although little is known of their range and migration outside of the breeding season, it is not thought that they migrate far in the winters. Occasional sightings have occurred on the coasts of Tasmania, southern Australia, the Chatham Islands, Stewart Island, and the southern New Zealand mainland.
Snares penguins nest in dense colonies under the tree cover of the Olearia forests or on coastal rocks. The Snares penguin is similarly coloured to other species of penguins, having a black head, back and flippers with a white belly. A bright-yellow crest, beginning at the base of the bill, runs along the upper part of the head on both sides and ends at the back of the head. It has a thick reddish-brown beak, traced with light pink skin at the base.
The penguin can make a large variety of vocal noises. It is difficult to verbally describe these noises, but they range from hisses and explosive cries when threatened to rhythmical braying and trumpeting sounds that can be heard from long distances at sea. One study found that about 60 percent of the mass of stomach contents from Snares penguins consisted of krill, 30 percent was fish, and about 10 percent was cephalopods. The researchers concluded that the number of fish otoliths and cephalopod beaks indicated the importance of these types of prey to adult penguins while at sea. Another study reports the diet consisting of about 55 percent krill, 24 percent fish, and 21 percent cephalopods, also suggesting that fish and cephalopods are more important prey types than the percentages of stomach composition indicate.
Foraging ecology
thumb|Diving Snares penguins
thumb|With crest standing erect, [[North East Island, New Zealand|North East Island]]
The foraging patterns of breeding Snares penguins are well defined. After shared incubation of eggs, males leave on two-week-long foraging trips, which has been found to be synchronised with spring plankton blooms, as they are reliable predictors of food sources. Snares penguins begin reproducing in the age range of 5 to 9 years old.
Egg incubation does not occur until both eggs have been laid, and they are usually incubated one in front of the other. The smaller, first-laid egg is often placed in the anterior position for incubation, which is thought to be the less favourable location since they have lower and more variable temperatures during incubation. Although the smaller, first egg receives less favourable incubation, it was found that egg-size dimorphism affects the hatching pattern in Snares penguins instead of egg incubation position. Both parents incubate the eggs. For the first ten days, they alternate. Then the male leaves for an extended period (about 12 days) to forage for food, while the mother stays with the eggs. When he returns, the roles are reversed. Also, upon his return, the pair engages in a display of bowing and trumpeting, which further strengthens their bond.
For the first three weeks after hatching, the male guards the chicks from predators while the female searches for food, returning each day to feed her offspring. The parents provide food for their young each day until it has moulted and can forage for its own food. The New Zealand government has taken action to protect the Snares Islands habitats and marine feeding grounds.