Penguins

Penguins

The name penguin is used for a group foil flightless birds of the southern hemisphere whose comical appearance, upright stance, and waddling gait belie their alibi-ties as the supreme swimmers and divers amongst birds. It was originally applied to tithe Great auk of the North Atlantic. Europeans first heard of penguins after the great exploring voyages of Vasco da Gama (1497-98) and Ferdinand Magellan(1519-22), which discovered Jackass and Magellanic penguins respectively, but many species were not known until the southern ocean was explored in the 18th century in search of the southern continent, to be known as Antarctica.

Penguins breed in habitats ranging from the bare lava shores of equatorial islands to sandy subtropical beaches, cool temperate forests, subantarctic grasslands, and ant arc-tic sea ice. They are, however, basically adapted to cool conditions and in tropical areas only occur where cold-water currents sexist, the egg within the influence of the Hum-bold Current along the western coast of South America and of the Beguile and Agulhas Currents around South Africa. Most species occur between 45 and 6 degrees south with the highest species diver-sixty in the New Zealand area and the Falkland Islands; the greatest numbers live around the coasts of Antarctica and on the subantarctic islands. Winter distributions and movements are little known.  

Although penguins show a wide range in weight and size they are remarkably similar in structure and plumage, being chiefly Blue-gray or blue-black above and mainly white below; species distinguishing marks (egg crests, crown, face and neck stripes, breast bands) are chiefly on the head and upper breast, being thus visible while the birds are swimming on the surface. The main chick plumages are gray or brown all over or have one of these colors along the back and white on the sides and under-surface. Juveniles’ plumage is usually verisimilar to that of adults, only differing in minor ways, egg the distinctiveness of ornamentation. Males are slightly larger than females, and those of crested penguins are notably so.

Penguins are densely covered by three layers of short feathers. They are highly streamlined, their wings reduced to strong, narrow, stiff flippers with which rapid pro-pulsing through water is achieved. The feet and shanks (tarsi) are short; the legs are set well back on the body and are used, with the tail, as rudders. On land penguins frequently rest on their heels with their stout tail feathers forming the prop. The short legs induce a waddling gait, but on ice, they can move rapidly by tobogganing on their bell lies. They have comparatively solid bones and generally weigh only a little less than water, thus reducing the energy required to dive. Bills are generally short and stout withal a powerful and painful grip. Emperor and King Penguins have long, slightly down-curved bills, possibly adapted for capturing fast-swimming fish and squid at considerable depths.

As well as having to swim efficiently penguins also need to keep warm in cool, often near-freezing waters. For this they have, in addition to a dense, very waterproof feather coat, a well-defined fat layer and a highly developed “heat-exchange” system of blood vessels in the flippers and legs ensuring that venous blood returning from exposed extremities is warmed up by the outgoing arterial blood, thus reducing heatless from the body core. Tropical penguins tend to overheat easily, so have relatively large flippers and areas of bare facial skinning in order to lose excess heat. They also live-in burrows so as to reduce direct exposure to sunlight.

The main prey of penguins is crustaceans, fish, and squid, which they chase, catch, and swallow underwater. Detection by a form of echolocation based on Resounds produced by their swimming movement. Fish are important in the diet of inshore feeders, egg Jackass, Little blue argentous penguins, and also of the deeper div-in King and Emperor penguins. Squid mar predominates in the food of the King pen&iiiand is frequently taken by Emperor AndRockhopper penguins and some Spheniscisspecies.

Krill are the principal prey of Adelie. Chinstrap, Genoa, and Macaroni penguin5 and other crustaceans are important Rockhopper penguins (and probably also Lithe other crested penguins) and Yellow-eyed penguins. Krill, like many minutes oceanic animals (zooplankton), tend to be absent from surface water during the day which is when penguins rear chicks this food is mainly at sea. However, they may still feed mainly at night (traveling and from their colony during the day) or us. Their diving ability to seek prey at depth -daytime.

The Little blue penguin is unusual in feeding its chicks well after nightfall; the smallest species it will have the shallowest diving capacity and may be more dependent on feeding around dusk when a greater proportion of its prey is near the surface. It may also be avoiding day-active predators by only coming ashore at night. In inshore-feeding species, both parents usually bring food to the chick each day. Adeline, ChinsIra, and crested penguin parents, however, are usually away at sea for more than a day soothe chick only receives one meal per day King and Emperor penguin chicks fee large meals at infrequent intervals, seldom more often than every three or four days. Only in large species do meals exceed ‘kg (but even quite young chicks of small penguins can easily accommodate 5002 of food. Indeed the capacity of young chicks is astounding and for much of their early growth, they are little more than pear-shaped sacks of food, supported by big feet and surmounted by a small head.

Emperor penguins lay their eggs in the fall. King penguin chicks overwinter at the breeding colony but are rarely fed during this period and grow mainly during the pre-vinous and subsequent summers (see p38Otherwise Antarctic and most subantarctic and cold temperate penguins breed in spring and summer. Breeding is highly synchronized within and between colonies. Gen too penguins and the more northerly of the crested penguins have longer breeding ea-sons and more variable timing. In Jackassand Galapagos penguins there are usually two main peaks of breeding, but lying occurs in all months of the year. This is also true of most populations of little blue penguins and in South Australia, some pairs are even able to raise broods successfully twice a year.

In most penguins, males come ashore first at the start of the breeding season to establish territories where they arson joined by their old partners or by new birds that they attract to the nest site. Penguins normally mate with the partners of previous years: in a colony of Yellow-eyed penguins Or percent of pairings lasted 2-6years, 12 percent 7-13 years, and the overall “divorce” rate was 14 percent per annum; of Little blue penguins one pairing lasted I years and the divorce rate was 18 percent per annum. In a major Adeline penguin study, however, no pairing lasted six years and the annual divorce rate was over 50 percent.

Macaroni penguins breed first when at least five years old; Emperor, King, Chinstrap, and Adeline penguins are at least three (females) or four (males), and a little blue, Yellow-eyed, Genoa and Jackasspenguins at least two years old. In Adeliepenguins very few one-year-olds visit the colony; many two-year-olds come for a few days around chick hatching but most birds visit first as three- and four-year-olds. Up to about seven years of age, Dailies arrive pro-aggressively earlier each season, make more visits and stay longer. Some females first breed at three years of age, and males at four, but most females and males wait another year or two and some males do not breed until eight.

Only Emperor and King Penguins lay a single egg; the rest normally lay two. In the Yellow-eyed penguin (and probably generally) age affects fertility so hatch-in success in a study colony was 32 percent, 92 percent, and 77 percent of eggs incubated by birds aged 2, 6, and 14-19 years respectively. In crested penguins the first egg of the clutch is very much smaller than the second; only in the Fiordland penguin do both eggs normally hatch and only one chick is ever reared this is an extreme form of a widespread adaptation ensuring that when food is scarce the smaller chick dies quickly and does not prejudice the survival of its sibling.

This system may be designed to cope with the high early eggless resulting from the considerable amount of fighting in the closely packed colonies, which in turn presumably results from sex-dual selection favoring aggressive males. Alternatively, when both eggs hatch the dif-ferrous size of the chicks may ensure that only one survives for long (i.e. there is a form of brood reduction). Neither explanation is entirely satisfactory. In other penguins, hatching is also staggered and these cans promote brood reduction, usually by favoring the first hatched chick.

All penguins have the capacity for storing substantial fat reserves (especially before the period of molting and fasting) but only the Emperor, King, Adeline, Chinstrap, and crested penguins undertake long fasts during the courtship, incubation, and brooding periods. During fasts lasting 13(o-115 days for brooding male Emperor penguins and 35 days for Adeline and crested penguins up to 45 percent of initial body weight may be lost. By contrast, Genoa, Yellow-eyed, little blue, and Jackass penguins usually change incubation every 1-2 days. Chicks grow rapidly, particularly in Antarctic species. After 2-3 weeks (6 weeks in Emperor and King Penguins) the chicks in open areas form large aggregations or crèches (Adelie, Gentoo, Emperor, and King Penguins) or small ones involving a few chicks from ajar-cent nests (Chinstrap, Jackass, crested penguins).

Once the molt is complete chicks usually start going to sea. In crested penguins, there is a rapid and complete exodus from the colony (almost all leave within one week) and almost certainly no further parental care. In Genoa penguins, free-swimming chicks return to shore periodically and there obtain food from their parents for at least a further two or three weeks. Some such parental care may occur in other species but it is unlikely that chicks are ever fed by their parents at sea. In most species, once chicks are indecent-dent the parents fatten quickly for a molting and fasting period of 2-6 weeks during which fat reserves are used twice as fast assign incubation. Immature birds usually complete molt before breeding birds start and at least in crested penguins the timing of this molt becomes later with age until the first breed-in attempt.

Compared with other seabirds, the survival of adult penguins from one year to tithe next is relatively low, being 70-80percent for Adeline, 86 percent for Macaroni,87 percent for Yellow-eyed, and 86 percent for Little blue, but 95 percent for Emperor penguins. Penguins are thus not particularly long-lived–records of 19-year-old Yellow-eyed and Adeline penguins being exceptional and the average lifespan is only about 20 years, except for Emperor penguins where it might be double this. Juvenile survival, however, is relatively high in most Antarctic species, except Emperor penguins where only some 20 percent of fledglings are reported to survive their first year, although this may be artificially low due to human interference.

Most penguins are highly social, both on land and at sea, and often breed in vast colonies, only defending the small areas around their nests. Courtship and mate-recognition behavior are most complex in the highly colonial Adeline, Chinstrap, Gen-too, and crested penguins, least so in the species that breed in dense vegetation, such as the Yellow-eyed penguin. Despite living in burrows. Jackass penguins, which usually breed in dense colonies, have fairly elaborate visual and vocal displays those of little blue penguins, whose burrows are more dispersed, and are more restrained. The social behavior of these penguins is largely nest oriented. In contrast, Emperor penguins, which have no nest site, show only behavior oriented to their partners. In King Penguins the incoming bird goes near its nest site and then calls and listens for a response. King and Emperor penguins are the only penguins where the two sexes can easily be distinguished by the characteristics of their calls.

Although flightless, adult penguins have few natural predators on land because they generally choose isolated breeding sites and their beaks and flippers are effective weapons (they are, however, vulnerable to larger introduced mammals). Eggs and chicks are taken by scubas and a variety of other predatory birds. At sea Killer whales, Leopard seals, and other seals and sharks catch penguins, but the extent of this predation is most of the local significance. In fact, the populations of several species of Ant arc-tic penguins (especially Chinstraps) seem to have increased appreciably in recent decades. This is attributed to the improved food supplies following the massive reduction in stocks of krill-eating baleen whales. Some King penguin populations have also increased, this perhaps being partly recovery from when they were killed so oil could be extracted from their blubber. In the past many penguin populations were reduced (and colonies eliminated) by egg collect-in for human consumption; in most cases, this is not a real problem today.

Three species of penguin are presently endangered. Galapagos penguins, with an atonal population of about 5,00o pairs, breed only on two islands in the Galapagos Archipelago. On one they are now seriously menaced by the presence of feral dogs, although an eradication program has been started. Yellow-eyed penguins have declined to fewer than 5,00o pairs, chiefly because of changing patterns of land use and other human disturbance in the coastal dune systems of New Zealand where they breed. Fortunately, populations on off-lying islands, where protection is more feasible, have suffered less. Both the Jackass and the Humboldt penguins occur in highly pro-ductile oceanic upwelling systems of nutrients that support large fishing industries. Populations of these species have decreased alarmingly, initially due to egg removal and guano collection, subsequently because of competition for food; the fishing industries off the west coasts of South America and South Africa both depend, as do penguins, on anchovies and pilchards. The survival of these two species, therefore, depends on compromises between fish-stock exploitation and conservation.

All penguins are highly vulnerable to oil pollution. This is a particularly serious threat to the Jackass penguin, as many Jack-ass colonies lie near the tanker routes around the Cape of Good Hope. Thousands of Magellanic penguins have died in oiling incidents in the Straits of Magellan. Jackasspenguins have been successfully cleaned and returned to their colonies where many have subsequently bred but this is a time-consuming and expensive operation. Com-metrical fishing practices, whether existing ones for anchovies or developing ones for krill, pose an increasing threat.

Diving in Penguins

Penguins are probably better adapted for life at sea than any other group of birds. Recently reliable information on their swimming and diving abilities has become available.

Although credited with swimming speeds of up to 6okm/h (37mph) all accurate measurements of normal swimming for Emperor, Adeline, and Jackass penguins gave speeds of 5 10 km/h (3-6mph). In short bursts and particularly when “proposing” (swimming motion in which penguins briefly leave the water) faster speeds May well be achieved. The purpose of proposing is uncertain; it might confuse underwater seal predators, achieve faster speeds by reducing drag when traveling in air or allow breathing without hindering movement at a fast speed. For Genoa, Chinstrap, and Macaroni penguins dive durations are usually 0.5-1.5 minutes, seldom exceeding 2 minutes. InJackass and Emperor penguins, however, the mean dive time is 2.5 minutes with a maximum of 5 minutes in Jackass and over 18 minutes in Emperors.

Diving depths have been measured, with “pressure-sensitive” recorders, for four species. Six Emperor penguin dives terminated at depths from 45-265m (I 50-87oft). Of2, 595 King penguin dives half were deeper than 50 m (165ft), and two were greater than 240 m (790ft). By contrast 1, of 110 Chinstrap Penguin dives 90 percent were shallower than 45 m (5oft), 40 percent less than have suffered less. Both the Jackass and the Humboldt penguins occur in highly pro-ductile oceanic upwelling systems of nutrients that support large fishing industries. Populations of these species have decreased alarmingly, initially due to egg removal and guano collection, subsequently because of competition for food; the fishing industries off the west coasts of South America and South Africa both depend, as do penguins, on anchovies and pilchards. The survival of these two species, therefore, depends on compromises between fish-stock exploitation and conservation.

All penguins are highly vulnerable to oil pollution. This is a particularly serious threat to the Jackass penguin, as many Jack-ass colonies lie near the tanker routes around the Cape of Good Hope. Thousands of Magellanic penguins have died in oiling incidents in the Straits of Magellan. Jackasspenguins have been successfully cleaned and returned to their colonies where many have subsequently bred but this is a time-consuming and expensive operation. Com-metrical fishing practices, whether existing ones for anchovies or developing ones for krill, pose an increasing threat.

Emperor penguins, when breeding, endure the coldest conditions faced by any bird: the frozen wastes of the Antarctic sea ice, where the average temperature is   20°C ( 4°F) and mean wind speed is 25km/h (16mph), sometimes reaching 75km/h (47mph). Emperor penguin breeding colonies form in the fall (mid-May) when courting takes place and females each lay a single egg on the newly formed ice. The males assume the job of incubating the eggs, each holding his partner’s egg on his feet for 6o days. When the eggs hatch both parents feed the chicks, from late winter and through the spring, soothe young who are ready for independence in the summer before the sea ice returns.

This breeding arrangement prompts two questions. Firstly, why do Emperor penguins raise their young at the worst time of year? Secondly, how do the penguins survive in winter conditions?

An answer to the first question seems to be that if Emperor penguins were to breeding the summer (a short season in the Antarctic, only four months long) they would not complete their breeding cycle before the onset of winter. Even when the chicks fledge, in late spring, they are only a percent of adult weight, which is the lowest proportion for any penguin, and juvenile mortality is high. The adults, however, are able to breed annually.

The means by whereby Emperor penguins survive in harsh conditions are several remarkable physiological and behavioral adaptations, all stemming from the need to minimize the loss of heat and the expenditure of energy.

The body size of Emperor penguins and their shape gives a relatively low surface-to-volume ratio and their flippers and bill are 25 percent smaller as a proportion of body size than in any other penguin. Heatless is further reduced by the extreme proliferation of their blood-vessel heat-exchange system(twice as extensive as that of King penguins), by recovering in the nasal pass-ages So percent of the heat added to cold inhaled air, and by the excellent insulation provided by very long double-layered, high-density feathers which completely cover the legs. Because in winter open water lies far away across the ice shelf. Feeding is difficult, changeovers at the nest are infrequent and long fasts (up to 120 days in males. and 64 days in females) are essential. Their large size enables storage of the big fat reserves needed for this. 

In large groups (up to 5,000 birds) and reducing activity to a minimum. The huddle as awhile moves very slowly downwind and windward birds move along the flanks and then into the center until they are once again exposed at the rear so that no birds are continually exposed on the edge of the group. All this is feasible only because Emperor penguins have developed the ability to move with their egg on their feet and cover it (and the young chick) with a vouch-like fold of abdominal skin. They have also suppressed nearly all aggressive behavior.

King penguins, the other species of large penguins, have a very different solution to the problem of breeding in the short sum-mars. They take over a year for a successful breeding attempt and cannot breed more frequently than two years in three. They have two main laying seasons, November – December and February, March, and most of the time any colony contains adults, eggs, and chicks at many stages of molt, incubation, and growth respectively. From the eggs laid in late November or early December chicks are reared to 8o percent of adult weight by June and fed sporadically (fasts of two months or so with an overall chick weight loss of about 4o percent) through the winter until September when regular feeding resumes until the chicks depart in November December. The adults then have to molt and cannot play again until February or March. Chicks produced from these eggs are much smaller when the winter comes (and many die), and they donor fledge until the following January- February.

See more: TINAMOUS