Penguins are flightless birds found only in the Southern Hemisphere (excepting the Galapagos penguin which lives on the Equator and could therefore claim to ‘visit’ the Northern Hemisphere from time to time!) and live in the oceans, coming ashore to breed along remote costs and islands, or fast ice (in the case of Emperor penguins).
Penguins are medium to large birds (1-40 kg; 40-115 cm) with a thick layer of fat beneath the skin. They walk on short legs with an often comical, upright posture. Their stiff wings are modified as flippers and cannot be folded against the body. Penguins dive well and use their flippers to swim underwater in pursuit of prey items. Prey items include anchovies, pilchards, cuttlefish, squid, and krill. Adult plumage is blue-black or gray dorsally (back) and white ventrally (front), sometimes with distinctive feathered plumes or colouring around the head and neck.
The largest species is the Emperor penguin: with a height up to about 1.1 m tall and weight of 35 kg or more. The smallest is the Little penguin (sometimes known as the Blue or Fairy penguin), which stands only around 40 cm tall and weighs about 1 kg.
Most penguins breed in large colonies, one of the largest being the Macaroni penguin colony in South Georgia, which is estimated to be five million pairs. Antarctic, sub-Arctic and cold temperate penguins breed in either spring or summer, whereas species in warmer climes have more continuous breeding seasons. Penguin nests range from shallow dishes of pebbles and vegetation, to holes dug in soft soil, to rocky depressions, to the space between the top of the feet and the pouch-like fold of abdominal skin. Nesting areas are diverse and include small caves, burrows, coastal forests, and pack ice. Females lay one to two whitish eggs per clutch, with two to four days between egg laying.
Often the younger of two chicks will not survive. Young chicks are quite undeveloped and need care and warmth from the parents. In some species chicks remain with and are regularly fed by adults until fledged at 10-52 weeks. In other species the chicks may be fed till nearly adult size, then fast for several months while huddling with other chicks for warmth in a nursery. The average age of sexual maturity differs between species, ranging from two to five years old and life expectancy is up to 20 years. Penguins are considered monogamous and individuals often nest at the same nest site, with the same partner from the previous year. In some species, up to 13 year pairings have been observed. Courtship displays are varied and complex, and may include loud raucous vocalizations, 'mutual ecstatic displays’ (mate recognition behaviors), and beak slapping (or bill-fencing displays).
Overall, penguin males and females share the parental care duties, but incubation, brooding, and feeding-fasting cycles are diverse and complex. Some species begin fasting at the onset of the breeding season. In some species males and females share incubation, whereas in others incubation is primarily uniparental. Incubation duration ranges from 30-64 days, whereas parental incubation shifts may range from 5-64 days. Usually the male takes the first incubation shift after the female has laid the clutch. One of the longest incubation and fasting shifts occurs in the Emperor penguin. During the Antarctic winter, the female Emperor penguin lays one egg then departs to feed at sea. The male fasts while incubating for 60 days till the female returns at hatching time. At that point the female begins brood care while the male goes to feed at sea. Contrastingly, during the Antarctic summer the female Chinstrap penguin lays two eggs. The female then fasts while incubating for 30 days until the male returns from feeding at sea.
Some penguins waddle along shorelines and ice, whereas others hop from rock to rock. When on ice or snow, penguins can move swiftly by tobogganing (sliding along propelled by wings and feet). Penguins also use their modified wings as flippers to swim underwater. The Emperor penguin is an exceptional diver and can stay submerged for 18 minutes and dive as deep as 500 meters. Swimming speeds average two to three knots, but may reach 15-20 knots for short distances. Swimming often includes porpoising (repeatedly breaking the water's surface with enough momentum to lift the bird into the air for about one meter.)
Penguins are highly social, oftentimes breeding in large colonies. Some species forage cooperatively and may dive synchronously while foraging in small or large groups. Species that breed in large colonies often have elaborate visual and vocal displays. Vocalizations are characterized as loud, short braying. In colonial species in which chicks group together in a nursery (or crèche) recognition of mates and offspring seems based on individually distinguishable calls.
Historically penguins were hunted and boiled to extract oil from the heavy layer of fat beneath the skin. At the turn of the century, approximately 150,000 Royal penguins (Edypes schlegeli) were harvested each year for 20 years from Macquarie Island (located south of New Zealand). On islands off of the coasts of Peru and Chile, penguin eggs and guano (dry bird droppings) are collected for local use.
Twelve penguin species are included in the IUCN Red List of Threatened Species, three of those (Eudyptes sclateri, Megadytpes antipodes, Spheniscus mendiculus) are listed as Endangered. Major threats to wild populations include: hybridization, destruction of breeding habitat, human disturbance, egg and guano collection, predation by introduced mammals, commercial fishing, and oil spills.
(Penguins, John Sparks and Tony Soper, Facts on File Publications, Oxford, 1987).