Penguins

Task 5

David Attenborough

Educated as a zoologist at Cambridge University in England, David Attenbor­ough has for many years been associated with the British Broadcasting Corpo­ration (BBC). He first produced a program titled Zoo Quest, which ran for several years. His next venture for the BBC was Life on Earth, a series adapt­ed from the book of the same name, from which this excerpt is taken.

The characteristic birds of the Antarctic, which are often taken, in­deed, as the very symbol of the far frozen south, are, of course, the pen­guins. In fact, the evidence of fossils suggests that though the family originated in the southern hemisphere, it did so in the warmer parts of it. Even today, some species of penguin live in the relatively warm wa­ters of southern Africa and south Australia. One lives actually on the equator, in the Galapagos. Penguins are superbly adapted to the swim­ming life. Their wings have become modified into flippers with which they beat the water and drive themselves along. Their feet are used for steering and are placed in the best position for the purpose, at the very end of their body. This gives them their characteristic upright stance when they come out of water. Swimming everywhere demands good insulation and the penguins have developed their feathers to provide it. They are very long and thin, with tips that turn downwards towards the body. The shaft not only has filaments along the blade but, at the base, fluffy tufts that mat together and form a layer that is virtually impene­trable to wind or water. This feather coat covers more of their body than does that of any other bird. It extends low down on the legs of most of them, and the little Adelie penguin, which is one of only two species that lives on Antarctica, even has feathers growing on its stubby beak. Underneath this feather coat is a layer of blubber. So effectively protected are penguins that, like the vicuna, they run a real risk of over­heating. They deal with that when necessary by ruffling their feathers and by holding their flippers out from their body to increase their radi­ating surface.

With such efficient insulation penguins have been able to colonise most of the waters of the southern oceans and in places they flourish in astronomic numbers. On Zavodovski, a small volcanic island in the South Sandwich group only 6 kilometres across, 14 million pairs of chinstrap penguins nest. They are small creatures, standing no higher than a man's knees. At the beginning of the Antarctic summer they come in to land, the huge swell hurling them on to the rocks with such violence that they seem certain to be smashed. But they have the re­silience of rubber balls and as the surf drains back from the rocks it leaves them unharmed and undismayed and they waddle perkily in­land. There on the bare volcanic ash they excavate simple scoops, squabbling ferociously and with ear-splitting shrieks over the pebbles with which they want to line them. In these meagre scrapes, they lay two eggs. The male incubates them while the female goes down to feed. If, as sometimes happens, the pair have chosen to nest in a gully where the ash is underlain by ice, then the heat of his body will melt the ice which drains away leaving him with his eggs sitting, in a rather bewil­dered way, in a deep hole. When the young hatch, the parents take it in turn to feed them. They grow rapidly so that by the time the short Antarctic summer is over, they are fully fledged and capable of swim­ming and feeding for themselves.

The largest of all the penguins is the emperor. It stands waist-high to a man and weighs 16 kilos, which makes it one of the biggest and heaviest of all sea birds. This great size may well be an adaptation to the cold, for the emperor lives and breeds on the Antarctic continent itself and is the only animal of any kind that is able to live through the ex­treme cold of the Antarctic interior during the winter. However, while their size undoubtedly helps them to retain heat, it also causes them great difficulties. Penguin chicks cannot feed themselves until they are fully developed and have their seagoing feathers. But large chicks take a long time to hatch and grow to their full size. Emperor penguin chicks cannot achieve this within the few weeks of the Antarctic summer as chinstrap or other smaller penguins manage to do. The emperors have dealt with this difficulty by adopting a breeding timetable that is exact­ly the reverse of that followed by most other birds. Instead of laying in the spring and rearing their offspring through the warmer months of summer when food is easy to get, the emperors start the whole process at the beginning of winter.

They spend the summer feeding at sea and at the end of it are as fat and as fit as they will ever be. In March, a few weeks before the long darkness of the winter begins, the adults come ashore on the sea-ice. It already extends a considerable way out from the shore and the pen­guins have to walk south for many miles to reach their traditional breeding grounds close to the coast. Throughout the dark months of April and May, the birds display to one another and finally mate. The pair claim no particular territory for themselves, nor make any nest, for they are standing on sea-ice and there is no vegetation or stones with which to line a scrape. The female produces just one egg, large and very rich in yolk. As soon as it emerges, she must lift it from the surface of the ice before it freezes. She does this by pushing it towards her toes with the underside of her beak and taking it up on to the top of her feet. There it is covered by a fold of feathered skin that hangs down from her abdomen. Almost immediately her mate comes to her and in a ceremony that is the climax of the breeding ritual, takes the egg from her on to his own feet and tucks it beneath his own apron. Her imme­diate task is done. She leaves him and sets off through the deepening darkness to the edge of the sea-ice where she can at last feed. But winter is now more advanced and the ice extends even farther away from the coast. She may, therefore, have to travel as much as 150 kilometres be­fore she reaches open water.

Meanwhile, her mate has remained standing upright, his precious egg on his feet, warm beneath his stomach fold. He does little, shuffling around to huddle together with the rest of the incubating males so that they give one another a little protection, turning his back against the driving snow and the screaming winds. He has no energy to waste on unnecessary movement or needless displays. When he first arrived here from the sea, he had a thick layer of fat beneath his feathers that made up almost half his body weight. He has already drawn upon that to sus­tain him through the exertions of his courtship. Now it must last him for another two months while he incubates his egg.

At last, sixty days after it was laid, the egg hatches. The young chick is not yet able to generate its own body heat and remains squatting on its father's feet, beneath his apron and warmed by his body. Almost un­believably, the male manages to find from his stomach enough food to regurgitate and provide a meal to his newly-hatched offspring. And then, with extraordinary accuracy of timing, the female reappears. She has put on a great deal of weight. There is no nest site for her to remem­ber. The male, in any case, may have shuffled quite a long way across the ice from where she last left him. She finds him by calling and recognising the individual tones of his reply. As soon as the pair are reunited, the female gives their chick a feed of regurgitated half-digested fish. The re­union is a critical one. If she had been caught by a leopard seal and failed to return, the chick would die of starvation within the next few days. Even if she is a day or so late, she may not be in time to provide it with the food it urgently needs. It will have perished before she reaches it.

The male, having stood and starved for weeks, is now free to find food for himself. Leaving the chick in the charge of his mate, he sets off for the sea. He is pitifully thin, having lost at least a third of his weight, but if he succeeds in reaching the edge of the ice, he dives into the sea and begins to gorge. For two weeks, he has a holiday. Then with a stom­ach and a crop full of fish, he sets off on the long trek back to his chick.

The youngster has had nothing more to eat than the fish carried in by the female, and some juice from her stomach. It is more than ready for further food from its father. It is still dressed in its chick's coat of fluffy grey feathers. All the chicks stand together in a huddle, but each is nonetheless recognisable individually to its parents by its voice. For the remaining weeks of the winter, the parents take it in turn to go fish­ing and bring back food for their youngster. At long last, the horizon begins to lighten, the temperature rises infinitesimally and cracks begin to appear in the sea-ice. Leads of open water develop closer and closer to the nurseries. Eventually one comes close enough for the chicks to reach. They shuffle down to it and dive in, excellent swimmers from the moment they hit the water. The adult birds join them in the feast­ing. They have a mere two months to restore their fat reserves before they must start the whole cycle over again.

The breeding process has been fraught with dangers and difficulties. Safety margins have been tiny. Weather just fractionally worse than usual, fishing just a little less productive, a parent just a day or so late—any such variation could result in the death of the chick. The ma­jority, in fact, do die. If four out of ten of them reach maturity, the em­perors have had a good year.

Дата добавления: 2015-10-21