provided by EG-BAMM, Maud Poisbleau & Laurent Demongin
Southern rockhopper penguins belong to the crested penguins, the largest genus of the Spheniciforms including seven other species of Eudyptes: eastern rockhopper penguin Eudyptes filholi, northern rockhopper penguin Eudyptes moseleyi, macaroni penguin Eudyptes chrysolophus, royal penguin Eudyptes schlegeli, Fiordland penguin Eudyptes pachyrhynchus, Snares penguin Eudyptes robustus and erect-crested penguin Eudyptes sclateri. The three subspecies of rockhopper penguins have recently been elevated to species level although, to date, BirdLife International recognises only two species (the southern rockhopper penguin Eudyptes chrysocome with the two subspecies chrysocome and filholi, and the northern rockhopper penguin Eudyptes moseleyi).
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The distribution of Southern rockhopper penguins is limited to the Falkland Islands/Malvinas (about 35 colonies) and the South American islands around Tierra del Fuego (7 islands in Chile, 2 in Argentina). Vagrant birds have been reported from the Antarctic Peninsula (64°8'S), Brazil (about 30°S), South Africa (about 33°S) and the Snares Islands, south of New Zealand.
Southern rockhopper penguins dive to 20 - 60 meters depth for 1 min on average with a maximum depth of 113 m and 4 min duration.
The timing of the breeding cycle of the southern rockhopper penguin is remarkably constant between years, at least in the Falkland Islands where they are studied in detail. Here, they can breed for the first time when they are only three years old and adults breed every year, except in years of very poor environmental conditions. Nest site and mate fidelity are high. They tend to come back the colony to lay at the same date every year. The populations from South America, which are further from the Antarctic Polar Front than the ones from the Falklands, breed a few weeks earlier.
In the Falkland Islands, southern rockhopper penguins return from their winter migration at the beginning of October, the males arriving a few days before the females. The females start to lay in the last week of October. The laying period is highly synchronous, lasting about 10-14 days within a colony. The clutch size is always two eggs that are laid four days apart. With an average weight of 118 g, the second egg (B-egg) is about 20% bigger than the first one (A-egg) that averages 92 g. The incubation starts only when the B-egg is laid and lasts 32-34 days. The females take on the first incubation shift while the males forage at sea for about two weeks. By the time the males depart, the have fasted for six weeks and, their body mass is about half of their arrival mass. When males return, the females depart the colony (after around 7 weeks of fasting) and usually come back just before hatching. The length of this foraging trip varies individually; some females return every day to the colony. The eggs are always attended. Otherwise, they would be quickly predated. Eggs lost to predation or lost by accident are never replaced.
The males care for the chicks for about three weeks after hatching while the females provision offspring regularly, usually every day. After the chicks have entered the crèches, males make a short trip to regain condition after their second fasting period. Then both parents feed the chicks until they fledge. The chicks moult when they are about 40 days old and the moult lasts about two weeks. At the Falkland Islands, chicks normally fledge at the age of about ten weeks during the first half of February. The adults depart the colonies and go to sea to fatten up before returning to their breeding colonies to moult. Adults fast again during the 3-4 weeks of moult. Between mid-April and mid-May, they return to sea for five months for their winter migration.
Breeding success is highly variable among colonies and between years, ranging from 0.35 to 0.69 in the Falkland but being only 0.23 - 0.31 at Staten Island (Argentina) during two seasons. In the Falklands, the annual survival rate of adults can reach up to 96% and the return rate of juveniles three years after hatching averages 80% during years with good conditions. These rates are almost the highest of any penguin species, which is exceptional for such a small species. However, these rates can be much lower if conditions are bad, especially in case of food shortage prior to moult or during harmful algal blooms.
The main predators of eggs and chicks are brown skuas Catharacta antarctica antarctica and striated caracaras Phalcoboenus australis, and additionally kelp gulls Larus dominicanus. Other scavengers are dolphin gulls Larus scoresbii, turkey vultures Cathartes aura, southern giant petrels Macronectes giganteus, Chilean skuas Catharacta chilensis, crested caracaras Caracara plancus or even cats that take mainly abandoned eggs and dead chicks and adults. At sea, birds can be killed by sea lions, fur seals and maybe by southern giant petrels.
Southern rockhopper penguins breed on islands that were initially free of terrestrial predators, such as cats and rats, before humans introduced them. The breeding colonies range from sea level sites to cliff-tops, and are sometimes located inland. The birds are able to climb steep rocks by small jumps. Their claws leave striations in the rocks on their way to the colony. Nests are very basic and usually comprise only a small cup in the soil, between rocks or under tussock. Nesting material is limited to small stones and some vegetation. At the Falkland Islands, they can nest amongst black-browed albatrosses Thalassarche melanophrys and king shags Phalacrocorax atriceps and may use old nests of black-browed albatrosses that they are forced to abandon if an albatross returns. King shags are also able to chase away the adults and to destroy their nests.
Southern rockhopper penguins are opportunistic feeders, preying on a mixture of fish, crustaceans and cephalopods, with great variations between years and among colonies. For example, at the Falkland Islands during incubation, the diet can consist almost exclusively of Euphausiid krill on one island, and be a mixture of fish larvae and krill on another. There is also evidence that squid is of greater importance in the penguins’ diet at the Falkland Islands than elsewhere. The diving behaviour varies as a function of the physical and biological characteristics of the foraging areas and of the particular stage of the breeding season.
The combination of the Falklands and Humboldt currents carrying cold and nutrient-rich waters northwards and to the continental shelf produces highly productive foraging areas along the South-American coasts. During the breeding season, the foraging trips of southern rockhopper penguins last up to two weeks between the incubation shifts but less than one day during crèche. On the trips during incubation, the adults from the Falklands spent more time over the Patagonian Shelf c. 140 km to the north of the Falklands than the adults from Staten Island (Argentina) that may forage over the shelf break to the east and south-east. The foraging activity of birds from Noir Island (Chile) is probably concentrated over the huge continental shelf in the southeast Pacific Ocean with the colony located 60 km from the shelf slope.
Usually, the second-laid egg (B-egg) hatches one day before the first-laid egg (A-egg). This phenomenon known as "reversed hatching asynchrony" and the fact that the B-egg is bigger than the A-egg are shared by all crested penguins and is unique among birds. Many hypotheses have been suggested and experiments have been conducted to understand these phenomena, but the mechanisms are not yet fully identified. The A-chick is smaller than the B-chick and hatches second. A-chicks therefore have a significant initial handicap, as they cannot compete for food against their older and bigger B-chick siblings. Consequently, A-chicks usually die of starvation or are predated within few days after hatching. However, if an A-chick is alone in the nest (B-egg lost or predated during incubation), it has the same capacity to fledge as a B-chick. Rarely parents are able to raise twins and it seems to happen only at the Falkland Islands.
During the non-breeding season, southern rockhopper penguins migrate mainly along the Patagonian Shelf several hundred km to the north of the Falklands, between the Falklands and the Argentinian coast, over the Burdwood Bank, an isolated extension of the Patagonian Shelf to the south of the Falkland Islands, and around Tierra del Fuego up to 92°W in the Pacific ocean.
The size of the colonies varies from a few dozen nests to several thousands. The nest density ranges from 0.3 to 1.30 nest/m2.
Hybridisation with erect-crested and macaroni penguins is known to occur at the Falkland Islands.
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