Pinguino macaroni

Identificazione

The macaroni penguin is a large, crested penguin, similar in appearance to other members of the genus Eudyptes. An adult bird has an average length of around 70 cm (28 in); the weight varies markedly depending on time of year and sex. Males average from 3.3 kg (7 lb) after incubating, or 3.7 kg (8 lb) after moult to 6.4 kg (14 lb) before moult, while females average 3.2 kg (7 lb) after to 5.7 kg (13 lb) before moult. Among standard measurements, the thick bill (from the gape) measures 7 to 8 cm (2.8 to 3.1 in), the culmen being around a centimetre less. The wing, from the shoulder to the tip, is around 20.4 cm (8.0 in) and the tail is 9–10 cm (3.5–3.9 in) long. The head, chin, throat, and upper parts are black and sharply demarcated against the white under parts. The black plumage has a bluish sheen when new and brownish when old. The most striking feature is the yellow crest that arises from a patch on the centre of the forehead, and extends horizontally backwards to the nape. The flippers are blue-black on the upper surface with a white trailing edge, and mainly white underneath with a black tip and leading edge. The large, bulbous bill is orange-brown. The iris is red and a patch of pinkish bare skin is found from the base of the bill to the eye. The legs and feet are pink. The male and female are similar in appearance; males tend to be slightly larger. Males also bear relatively larger bills, which average around 6.1 cm (2.4 in) compared to 5.4 cm (2.1 in) in females; this feature has been used to tell the sexes apart.<p>Immature birds are distinguished by their smaller size, smaller, duller-brown bill, dark grey chin and throat, and absent or underdeveloped head plumes, often just a scattering of yellow feathers. The crest is fully developed in birds aged three to four years, a year or two before breeding age.<p>Macaroni penguins moult once a year, a process in which they replace all of their old feathers. They spend around two weeks accumulating fat before moulting because they do not feed during the moult, as they cannot enter the water to forage for food without feathers. The process typically takes three to four weeks, which they spend sitting ashore. Once finished, they go back to sea and return to their colonies to mate in the spring. Overall survival rates are poorly known; the successful return of breeding adults at South Georgia Island varied between 49% and 78% over three years, and around 10% of those that did return did not breed the following year.

Tassonomia

The macaroni penguin was described from the Falkland Islands in 1837 by German naturalist Johann Friedrich von Brandt. It is one of six or so species in the genus Eudyptes, collectively known as crested penguins. The genus name is derived from the Ancient Greek words eu "good", and dyptes "diver". The specific name chrysolophus is derived from the Greek words chryse "golden", and lophos "crest".<p>The common name was recorded from the early 19th century in the Falkland Islands. English sailors apparently named the species for its conspicuous yellow crest. It is similar to the then fashionable Macaroni.<p>Molecular clock evidence using DNA suggests the macaroni penguin diverged from its closest relative, the royal penguin (Eudyptes schlegeli), around 1.5 million years ago. The two have generally been considered different species, but the close similarities of their DNA sequences has led some, such as Australian ornithologists Les Christidis and Walter Boles, to treat the royal penguin as a subspecies of the macaroni penguin. The two species are very similar in appearance; the royal penguin has a white face instead of the usually black face of the macaroni penguin. Interbreeding with the Indo-Pacific subspecies of the southern rockhopper penguin (E. chrysocome filholi) has been reported at Heard and Marion Islands, with three hybrid subspecies recorded there by a 1987–88 Australian National Antarctic Research Expedition.

Nome scientifico

Eudyptes chrysolophus

Autorità

(Brandt, JF, 1837)

Ordine

Sfenisciformi

Famiglia

Spheniscidae

Genere

Eudyptes

Areale e habitat

A 1993 review estimated that the macaroni was the most abundant species of penguin, with a minimum of 11,841,600 pairs worldwide. Macaroni penguins range from the Subantarctic to the Antarctic Peninsula; at least 216 breeding colonies at 50 sites have been recorded. In South America, macaroni penguins are found in southern Chile, the Falkland Islands, South Georgia and the South Sandwich Islands, and South Orkney Islands. They also occupy much of Antarctica and the Antarctic Peninsula, including the northern South Shetland Islands, Bouvet Island, the Prince Edward and Marion islands, the Crozet Islands, the Kerguelen Islands, and the Heard and McDonald Islands. While foraging for food, groups will range north to the islands off Australia, New Zealand, southern Brazil, Tristan da Cunha, and South Africa.

Migrazione

Complete migrants

Comportamento

The diet of the macaroni penguin consists of a variety of crustaceans, squid and fish; the proportions that each makes up vary with locality and season. Krill, particularly Antarctic krill (Euphausia superba), account for over 90% of food during breeding season. Cephalopods and small fish such as the marbled rockcod (Notothenia rossii), painted notie (Lepidonotothen larseni), Champsocephalus gunneri, the lanternfish species Krefftichthys anderssoni, Protomyctophum tenisoni and P. normani become more important during chick-rearing. Like several other penguin species, the macaroni penguin sometimes deliberately swallows small (10– to 30-mm-diameter) stones; this behaviour has been speculated to aid in providing ballast for deep-sea diving, or to help grind food, especially the exoskeletons of crustaceans which are a significant part of its diet.<p>Foraging for food is generally conducted on a daily basis, from dawn to dusk when they have chicks to feed. Overnight trips are sometimes made, especially as the chicks grow older; a 2008 study that used surgically implanted data loggers to track the movement of the birds showed the foraging trips become longer once the chick-rearing period is over. Birds venture out for 10–20 days during incubation and before the moult. Macaroni penguins are known to be the largest single consumer of marine resources among all of the seabirds, with an estimated take of 9.2 million tonnes of krill a year. Outside the breeding season, macaroni penguins tend to dive deeper, longer, and more efficiently during their winter migration than during the summer breeding season. Year round, foraging dives usually occur during daylight hours, but winter dives are more constrained by daylight due to the shorter days.<p>Foraging distance from colonies has been measured at around 50 km (31 mi) at South Georgia, offshore over the continental shelf, and anywhere from 59 to 303 kilometres (37 to 188 mi) at Marion Island. Macaroni penguins normally forage at depths of 15 to 70 m (49 to 230 ft), but have been recorded diving down to 100 m (330 ft) on occasions. Some night foraging does occur, but these dives are much shallower, ranging from only 3 to 6 m (9.8 to 19.7 ft) in depth. Dives rarely exceed two minutes in duration. All dives are V-shaped, and no time is spent at the sea bottom; about half the time on a foraging trip is spent diving. Birds have been calculated as catching from 4 to 16 krill or 40 to 50 amphipods per dive.<p>The macaroni penguin's predators consist of birds and aquatic mammals. The leopard seal (Hydrurga leptonyx), Antarctic fur seal (Arctocephalus gazella), Subantarctic fur seal (A. tropicalis), and killer whale (Orcinus orca) hunt adult macaroni penguins in the water. Macaroni colonies suffer comparatively low rates of predation if undisturbed; predators generally only take eggs and chicks that have been left unattended or abandoned. Skua species, the snowy sheathbill (Chionis alba), and kelp gull (Larus dominicanus) prey on eggs, and skuas and giant petrels also take chicks and sick or injured adult birds.

Conservazione

The population of macaroni penguins is estimated at around 18 million mature individuals; a substantial decline has been recorded in several locations. This includes a 50% reduction in the South Georgia population between the mid-1970s to mid-1990s, and the disappearance of the species from Isla Recalada in Southern Chile. This decline of the overall population in the last 30 years has resulted in the classification of the species as globally Vulnerable by the IUCN Red List of Threatened Species. Long-term monitoring programs are underway at a number of breeding colonies, and many of the islands that support breeding populations of this penguin are protected reserves. The Heard Islands and McDonald Islands are World Heritage Sites for the macaroni penguin. The macaroni penguin may be being impacted by commercial fishing and marine pollution. A 2008 study suggests the abilities of female penguins to reproduce may be negatively affected by climate- and fishing-induced reductions in krill density.

Tendenza della popolazione

declining