Northern rockhopper penguin  (Eudyptes moseleyi)

Classified as Endangered (EN) on the IUCN Red List (1).

Previously classed as a single species, the rockhopper penguin has now been split into a northern (Eudyptes moseleyi) and southern species (Eudyptes chrysocome) (3). Although both species are similar in appearance, the distinctive yellowish plumes extending from the yellow line above the eye are significantly longer and denser in the northern rockhopper penguin (2) (3). The body is small but robust, with slate-grey upperparts and white underparts, the bill is short and reddish-brown and the eyes are red. Juveniles can be identified by the lack of adult yellow markings (2).

The northern rockhopper penguin breeds on a number of Southern Ocean islands, with the largest populations found on the islands of Tristan da Cunha and Gough, and additional, smaller populations on the islands of Amsterdam and St Paul (4).

Nesting occurs on cliffs and rocky gullies, and chosen sites are usually situated near to freshwater, either natural springs or puddles (2).

A gregarious species, the northern rockhopper penguin breeds in large colonies that may comprise over a hundred thousand nests. Breeding pairs are monogamous, and usually return to the same nest every year (2). Egg-laying commences around August (3), with the female usually producing a clutch of two eggs of unequal size (2). Usually only the chick from the larger egg survives to maturity. Incubation takes around 33 days, with both parent birds taking it in turns to sit on the eggs for extended periods of a time, whilst the other forages for food. Incubation is aided by a bare patch of skin on the lower abdomen (known as a 'brood pouch') that allows greater heat transfer to the egg. Once hatched, the male will remain to brood the chick for the first 25 days, whilst the female regularly brings food back to the nest. After this time, the chick is able to leave the nest, and will congregate with other chicks in small groups known as 'crèches' whilst the parent birds forage (2).

In order to maintain its waterproof coat, the northern rockhopper penguin engages in frequent grooming, which helps to flatten the feathers and to spread a waxy substance that is secreted just below the tail. Grooming is also an important social bond between pairs. After breeding the northern rockhopper penguin forages extensively in order to build up fat reserves in preparation for its annual moult. It takes around 25 days for the penguin’s coat to be fully replaced, at which point it leaves the land and spends the winter months foraging at sea, before returning to shore to breed in the following spring (2). The diet of the northern rockhopper penguin is composed of a variety of oceanic species, such as crustaceans, squid, octopus and fish (4). Groups may often feed together and dives may be to depths of up to 100 metres (2).

A recent study of the northern rockhopper penguin population (published in 2009), has shown that well over one million birds have been lost from the breeding colonies on the islands of Tristan da Cunha and Gough. While this equates to declines of over 90 percent on both islands, on Gough this loss has occurred in just 45 years, whereas on the main island of Tristan, it has taken almost three times longer. The reasons for the swift decline on Gough are currently unknown, but the penguin may be suffering increased levels of predation, as well as competition for food, from the rapidly rising population of Subantarctic Fur Seals Arctocephalus tropicalis (5). Other factors may include increasing disturbance and pollution, introduced predators, reduced food supplies due to overfishing, and climate change (4).

While the northern rockhopper penguin population is being regularly monitored, in order to safeguard against further declines, it is imperative that the causes of the population crash be determined (4) (5). This should be targeted at all possible factors, including studies of interactions with commercial fisheries, the impact of the introduced predatory house mouse on chick survival on Gough Island (4), and the effects of fur seal predation and competition (5). Without the implementation of appropriate conservation measures, this charismatic species will continue to nose dive towards extinction (5).

To learn more about penguin conservation visit:

• International Penguin Conservation:
  http://www.penguins.cl
• Organisation for the Conservation of Penguins: English:
  http://www.seabirds.org Spanish:
  http://seabirds.org/chile.htm

For more information on this and other bird species please see:

• BirdLife International:
  http://www.birdlife.org