Adèlie – the walking bird
A mantle of snow shows the tracks of travelling Adèlie penguins heading towards their colonies for the summer breeding season. Only at this time of year do these hardy birds come ashore. The rest of their lives is lived out among the pack ice that surrounds Antarctica.
Four little black heads pop up together into a pool of dark blue water, a solitary liquid sapphire in a setting of endless white. In every direction, mile upon mile of flat, shimmering sea ice stretches as far as the eye can see. Its blinding brilliance lends an eerie glow termed “ice blink” to the underside of the low, murky cloud cover.
Only a few dark purplish areas of “water sky” in the distance reveal the presence of further ice-free patches beyond the horizon. It feels a harsh, sterile place. Yet Adèlie penguins endearingly named after the wife of 19th-century French explorer Dumont d’Urville are not only at ease in this frozen world, but at home.
It is late summer in the Ross Sea, some 2500 km almost due south of New Zealand. Leaning over the towering prow of the 12,300-tonne Russian icebreaker Kapitan Khlebnikov, I am surprised to hear clearly the penguins’ strident contact calls, despite the cutting wind that screams in my ears. Used only at sea, these otherworldly caws enable the sociable birds to keep in touch even in stormy conditions.
The penguins dart about in tight circles, appearing completely relaxed in this frigid realm that girdles the shores of Antarctica. As the ocean surface freezes and thaws with the changing seasons, the ice spreads and shrinks like a continent-sized crystalline skirt, nearly doubling Antarctica’s glacial expanse each winter. Ice is the Adèlie penguin’s universe. It defines the Adèlie’s existence more than that of any other penguin, and perhaps any other creature on Earth.
Firmly lodged in the frozen grip of the sea, our ship sits idle, yet I notice that the rigid surface all around is, in fact, moving. Floes the size of hockey fields are crunching and grinding against one another. Powerful ocean currents below and opposing winds above are exerting their dual control over the vast expanse of fragmented frozen sea the so-called pack ice shoving and shifting the entire mass this way and that in enormous swirls and gyres. Under this constant motion, cracks and fissures open and close, and large pools, like the one the penguins have just found, are forced open by tidal eddies. Expertly, the Adèlies track these weak points and use them to transit between the world above, which they need in order to breathe, and the one below, which provides them with their nourishment.
Sea ice up to two metres thick underpins the short and simple food chain that enables the penguins to exist here. Within its spongy layers, microscopic algae bloom in profusion as spring sunlight begins to filter through from above after the long, dark winter. As the ice melts the algae are released as a diatomaceous soup, which is grazed by dense swarms of krill, a shrimp-like crustacean with a complex multi-year life cycle. Krill, in their turn, are the Adèlie penguin’s primary prey.
As I watch, three more penguins surface in the pool. It is hard to imagine how these deep-diving birds manage to locate such a tiny opening in the virtually unbroken cover above them. For a moment they seem to hesitate, reluctant to leave the watery medium through which they move as effortlessly as fish. Then all at once they shoot up like squeezed cherry pips, landing feet first on the floe. Upright and amazingly nimble on their short legs, they dash about, flapping their flippers in the air like excited, gesticulating children. Just as quickly they stop, regroup and stare up at the monstrous hulk of black-painted steel that has come into their midst. We peer at each other from our very different worlds, the curiosity mutual.
Few other higher vertebrates share the Adèlie’s world of ice. Crab-eater and leopard seals are denizens of the loose pack, while Weddell seals inhabit mostly “fast ice” (sea ice still firmly attached to the shore), where they maintain breathing holes by sawing at the edges with their teeth. Ross seals limit themselves to regions where the densest, heaviest pack never breaks up. Orca, minke whales and humpback whales visit only the fringes of the ice skirt. Of these mammals, only orca and leopard seals prey on penguins.
The Adèlie penguin, standing scarcely 0.7 m tall and weighing not much over 5 kg, is the smallest of all warm-blooded aquatic animals in the Ross Sea. (It is just one-eighth the weight of the emperor penguin.) Since the ratio of heat loss to body mass increases with reduced size, it is testimony to the Adèlie’s insulatory and metabolic adaptations that the bird can survive in seas where temperatures stay at a constant year-round –1.8° C.
Penguin feathers are arranged like scales, their broad, flat, stiffly curving shafts overlapping tightly to form a sleek protective shell. At the base of the feathers grow secondary tendrils of fine downy filaments that serve as a dense, dry undergarment. The outer surface of this superb natural dry suit is kept completely waterproof by the application of oil from the preen gland, located at the base of the tail. Unlike the plumage of other birds, whose feathers grow in zones, a penguin’s sprouts evenly from its entire body—approximately 12 feathers per square centimetre. Adèlie feathers are longer than those of any other penguin species and even cover most of the bill, leaving just the horn-coloured tip bare. Beneath the snug swaddle of an Adèlie penguin’s feathers lies another form of insulation: an ample fat layer under the skin.
Metabolically, penguins have evolved to minimise temperature loss, with special heat-exchange chambers inside their windpipes to allow heat and moisture from exhaled air to be recaptured as they breathe in. Likewise, blood flow to their extremities is configured so that heat from outflowing arteries is transferred through the vessel walls to the cooler returning venous blood.
So efficient are the Adèlie’s heat-retaining mechanisms that it is in danger of overheating while on land. Even from the height of the ship’s bow I can see the feet of the penguins below me are flushed brilliant pink, as are the undersides of their flippers, which they are waving to and fro in the wind. Having just been swimming vigorously for long distances, they are clearly doing all they can to cool down.
For a few more minutes I watch my seven little ice birds. Their sleek, waterproof black-and-white plumage, enveloped in a film of water when they emerged from the sea and as shiny as if they were shrink-wrapped in cellophane, begins to fluff up as they allow air to penetrate and cool them. Then, as if on command, they set off southward across the ice, heading for the faint outline of a distant mountain range.
At the base of those mountains, some 50 km away, lies Cape Adare, in New Zealand’s Ross Dependency, where each year at this time some 280,000 pairs of Adèlies come together to raise their young in a frenzy of hyperactivity in what is the largest penguin colony in Antarctica.
With continuous daylight now upon them, and driven by the breeding imperative, the penguins display tremendous urgency. By following cracks and leads they have been able to swim far into the heart of the densest pack ice. But where, in spite of 24,000 ice breaking horsepower, our ship’s progress has been impeded by the solid floating layer, the Adèlies simply switch from water travel beneath and between ice floes to slightly more laborious locomotion over them.
For a while I watch the birds recede in a line, some waddling, others tobogganing,until they are but tiny black dots in the glaring distance. Their unerring purpose is relieve their fasting mates back at the nest, with whom they have been taking turns incubating their two eggs for the past five weeks. T heir inner clocks tell them that everywhere across the colony tiny, fuzzy, grey-black heads and hungry beaks are popping out of eggs in every nest, adding resolve to this long trudge across the lingering fast ice.
Another day passes aboard the icebreaker as it slowly crashes, bashes and crunches its way forward. Finally, we too arrive at Cape Adare: a dark, imposing headland of rock looming in the frosty whiteness. For the penguins, the important part of this stark domain is the extensive flats of morainal deposits sheltered from glacial ice by steep volcanic ramparts-their nesting grounds.
Long before we land we can detect the characteristic smell of penguin guano on the wind: a richly organic, not unpleasant, iodine laden odour that contrasts sharply with the otherwise pure Antarctic air. A pink hue, the residue of krill pigment, tinges the distant plains and slopes.
The shore is a bewildering hubbub. All along the gravelly beach, where slabs of storm-tossed ice are still pi led high along the tideline, wave upon wave of returning penguins hurry up the steep grade and fan out across the crowded colony as each bird makes a beeline for its nest, following a precise route among tens of thousands of neighbours. The cacophony of call s, the incessant motion of the penguin mass blanketing the land, the constant flow of commuters bustling to and from, the fights and chases that erupt when personal penguin space is invaded or when young marauders snatch a few prized pebbles to start building a nest of their own, the furious squawks of the victims of egg-plundering skuas, the exaggerated displays of reunited pairs, the sight of parents greeting new chicks- all this activity creates an almost inebriating atmosphere. I am witnessing the central drama of the Adèlie penguin ‘s life, in which timing is all.
The rookery spreads like a living carpet over every available patch of snow-free ground; over rolling ridges and far up impossibly steep gullies several kilometres inland. With nests often less than a metre apart, the penguins are packed as tightly as sports fans in a stadium, and fiercely defend their tiny patches of real estate. Hatching has caused numbers to swell to over a million birds, with both parents doting over two young chicks in almost every nest.
Like traffic arteries, long furrows of no-man’s-land filled with snow drift serve as the main commuting thorough fares between crowded stretches of moraine. Vehement brawls-penguin road rageerupt regularly, though the exact cause is usually impossible to determine in the confusion. Whatever its wrongdoing, the offending bird is invariably pounced upon with unrestrained fury, grabbed by the scruff of the neck and pummelled with fierce volleys of bony flippered thwacks. In its frantic attempts to escape, the culprit crashes and tumbles through neighbouring nests with
the attacker in hot pursuit, raisin g a cataract of further insults and beatings. Eventually the birds sort themselves out, shake off a few loose feathers and return, indignant but none the worse for a few blood splatters, to resume nest-guarding duties.
Yet should a skua a large, predatory gull like sea bird that nests on the periphery of the colony-come hawking overhead in search of unprotected chicks or eggs, the entire neighbourhood unites, shrieking with bills pointed skywards, and driving the intruder off should it dare to land nearby.
Even the relative penumbra that passes for summer night-time in the Ross Sea brings little relief from this frenetic rhythm of life. Every penguin in the colony, young or old, seems somehow to be aware that at 71° S the entire breeding process is a race against the clock.
The first birds to reach the colony, mostly males, arrived about two months ago, in late October, having navigated flawlessly across dozens of kilometres of fast ice in the deep chill of early spring. Within a few days each had located his nest of seasons past, even if it was still covered in snow. Soon the females came ashore, too, in most cases seeking their mates of previous years and reuniting with them in a celebration of screams and brays, head-waving and posturing—the ecstatic display.
Adèlies can express an amazing variety of behavioural cues by raising or slicking down their crest-like head feathers, rolling their white-rimmed eyes, ducking, bowing and waving their heads, and employing other body language. Appeasement, for example, is expressed by standing tall and thin with flippers held down against the side of the body. Defiance is shown by planting both feet far apart, waving flippers slowly straight out to either side and holding the head squarely up and averting it from side to side. Aggression is signalled by hunching forward and growling open-beaked with white-circled eyes glowering.
For the first two weeks ashore, each pair’s primary concern is to clean out the nest site, rebuild a good pebble mound, ward off territorial contenders and mate. Yet the male’s attachment to what has proved to be a good nest site runs deeper than his fidelity to a mate from a previous season. Secure, ice-free ground is so scarce, and the seasonal thaw so short, that the imperative to start breeding without losing a single day makes it paramount for him to hang on to his site while also finding a mate as quickly as possible, even if his known partner is not at hand.
As many as 99 per cent of males return to nest at the exact same spot they have used in previous years, whereas only about 70 per cent of pairs reunite. Some of the bloodiest fights in the colony take place when a late-returning female discovers her place has been usurped.
As soon as her two eggs have been laid, two to four days apart in mid-November, the female heads back to sea to feed, leaving her mate to take the first two-week incubation shift. Typically, the females have to cross long stretches of fast ice on foot to reach the sea. Once there, they criss-cross the dense pack while gorging on krill and other prey to regain condition lost while ashore.
If ice cover is extensive or food scarce, females may travel over 300 km during their post-laying break. By the time they return, their mates have been fasting for over a month. Gaunt, but free at last to return to the bountiful ocean, the males readily hand over incubation.
After another 10 days to two weeks with the female on duty, the shifts shorten. With hatching imminent and the ice break-up bringing open sea closer to shore, feeding journeys become less arduous, and the tempo of parental activity increases markedly in December as role swapping moves into high gear.
Then, suddenly, the 35-day incubation, during which the eggs cannot be left unattended for an instant, is over.
All around me I can see new mums and dads responding to shrill chick peeps with excited nods and bows. Carefully, they clear shards of eggshell from around the fragile hatchlings tucked between their feet. Within hours of emerging, the tiny chicks raise their wobbly heads, eyes only half open, and beg for food, for they, too, know innately that growing up quickly is vital in a land where summer lasts only a few weeks. Their besieging squeaks are answered with ready beakfuls of krill puree, dutifully carried back from the sea.
Hatching marks roughly the halfway point in the breeding season. Winter will soon return with brutal finality for any chick that does not mature in time. The penguins’ race against the clock becomes even more urgent. With young beaks requiring filling in ever-increasing quantities, the Adèlie parents must divide their time for the first few weeks of their chicks’ lives between securing food from the sea and sheltering their vulnerable offspring from harsh weather and marauding skuas.
Solicitously, they pour great gobs of pink krill slurry down the ravenous little gullets on demand. The chicks grow so fast that within days of hatching their bulging, pendulous stomachs look ready to burst. I’m sure I can see their girth expand with every feeding.
For penguin parents it is crucial that the summer break-up of the sea ice keeps pace with the food demands of their young, so that the distance between nesting and feeding grounds allows for quick delivery of meals and the regular change-over of parenting duties ideally every day, or every two at the most. Should the ice linger too long, necessitating lengthy trips, the chicks will either starve to death or grow too slowly to survive the coming winter.
If, on the other hand, the ice breaks up and melts too early, the ice-linked food chain that culminates in the dense krill swarms upon which the penguins depend is weakened, with the same outcome: chicks starving or left unattended, too young to fend for themselves, while both parents desperately seek food that is scattered too thinly or too far away.
One summer, on the opposite side of the Antarctic continent, among the islands of the South Orkney chain, I witnessed just such a tragedy as an entire colony was struck by a severe food shortage. Although the chicks there were less than two weeks old, the vast majority of parents were nowhere to be seen, having gone far out to sea in a desperate search for sustenance.
Making matters worse was the fact that the temperature was so balmy around 10° C that the moisture-laden sea breeze delivered a persistent drizzle to the island that turned the entire penguin colony into a krill-stained guano quagmire. Here and there, clusters of bedraggled chicks, soaked to the skin, huddled together pathetically for warmth, their downy coats splattered with mud.
Their normally rotund stomachs hung hollow and sagging. The only well-fed birds were the skuas, pecking languidly at dozens of trampled carcasses. A feeling of gloom hung over the beach as lone, exhausted parents returned with what food they could find. As they tried valiantly to call out to their own chicks, they were stormed by the starving hordes and driven back into the sea in a desperate free-for-all.
Disastrous summers like this have become more frequent in the past few decades around the Antarctic Peninsula, which is the northernmost and warmest part of the Adèlie’s range. As the planet follows its warming trend, US scientists working at Palmer Station, on the western side of the peninsula, report that average temperatures there have increased by nearly 3° C over the past 50 years. Concurrently, good winter sea-ice cover, upon which krill depend and which used to form, on average, four out of every five years in the 1950s, has been reduced to making an appearance only once or twice in the same period.
And that is not the only bad news for the Adèlies of the Antarctic Peninsula. Higher temperatures tend to increase precipitation, causing more snowfall on the nesting grounds in winter, which hampers breeding efforts as the summer melt inundates nest sites and rain and mud chills unprotected chicks just as I saw in the South Orkneys. Temperatures are becoming so high that ticks are now surviving the winter and plaguing nesting birds in spring.
As a result, population crashes have been recorded in several Adèlie rookeries around the Antarctic Peninsula. In five colonies near Palmer Station, the combined number of breeding pairs has dropped from 15,200 to 9200 in 25 years, while some smaller colonies have completely vanished. These findings have caused at least one ecologist, William Fraser, of Montana State University, to observe that Adèlies may be the “canaries in the coal mines” of global warming.
The infamous Antarctic ozone hole, resulting from fluorocarbon-induced thinning of the protective ozone layer in the upper atmosphere, is adding yet another unknown factor to a tricky equation. Unscreened by ozone gas, solar UV-B radiation, striking the Antarctic region in higher doses than ever before, is believed to be substantially reducing the productivity of the ice algae, and thus the krill on which the Adèlies depend.
If I once found the degree to which UV radiation can be harmful to living things a little hard to grasp, the point was driven home to me one spring when I found myself deep in the Weddell Sea at the peak of the annual ozone-depletion cycle. In just eight hours of exposure, several of my naturalist colleagues suffered second- and third-degree burns to exposed skin, having used sun-protection creams that did not live up to their claims. Yet penguins can wear neither sunscreen lotion nor tinted goggles. I am amazed and thankful that Adèlies have not been more severely affected. It would be a cruel irony if this hardy little penguin’s superb adaptations to extreme cold were its undoing in a warming world.
Fortunately, the Adèlie population in the Ross Sea, estimated at about one million breeding pairs, does not appear to be in decline. On the contrary, some rookeries are experiencing a population explosion. Perhaps global warming, while shrinking the Adèlie’s northern range, is extending its habitat southwards by making the fast ice in these extreme latitudes less tenacious.
Globally, Adèlie penguin numbers appear stable, or perhaps even on the rise. Like fur seals and some other penguin species, Adèlies may be responding to the availability of food sources left untapped following the extermination of whales over the past century and a half.
Leaving Cape Adare, our ship travels another 700 km deeper into the Ross Sea to the shores of Ross Island. A helicopter flight takes me across the remaining 10 km of impenetrable fast ice separating the icebreaker from Cape Royds, where the southernmost Adèlie rookery nestles at the foot of smouldering Mount Erebus. Even the renowned emperor penguin, which rears its young on the fast ice in winter, does not venture this far south to breed.
The atmosphere here is more subdued than at Cape Adare, as the season is well behind schedule, with adults still sitting on unhatched eggs. The barriers of fast ice and the lingering snow on the ground explain the delay. Yet even here, at 77° S, in most years the Adèlies manage to raise healthy chicks.
But what, I wondered, is the driving force that brings them to this extreme location? The answer, once again, seems to be the availability of ice-free terrain. Unlike emperors, Adèlies cannot carry their eggs on their feet to insulate them from the ice, and therefore depend on being able to lay them on solid ground. In all the vastness of the Ross Sea through which Adèlies range, there is a dearth of appropriate nesting areas, and it is principally this that determines the location of colonies.
Ice-free areas are precisely the places humans have sought for building huts and bases for exploration and scientific investigation. At Cape Adare, a small cluster of squat wooden structures still stands incongruously in the middle of the penguin colony. It was here, in 1899, that the Norwegian explorer Carstens Borchgrevink’s expedition became the first to overwinter on the Antarctic continent.
A more flagrant invasion of precious penguin domain took place at Cape Hallett, 110 km south of Cape Adare, when a combined American New Zealand team occupied an extensive swathe of the penguin colony to construct a research station on the occasion of the International Geophysical Year, in 1957. More recently, the French built a runway on an Adèlie penguin rookery on the far side of Antarctica.
But in each case the penguins ultimately prevailed. Cape Hallett Station was abandoned in 1973 after it burned down, and storm waves undermined the French airfield, leaving the resilient Adèlies to reclaim their stakes in the coveted Antarctic soil. Nowadays, Antarctic Treaty regulations, increasingly self-imposed by signatory nations, no longer permit such infringement of penguin rights.
Four weeks after seeing the chicks hatch at Cape Adare, I am back again, but the view that greets my eyes is utterly changed. Everywhere plump chicks almost as large as the adults waddle about, well fed to the point of obesity. No longer nest-bound, they gather in huge, tightly packed creches while their parents are out feeding. The low snow banks that had served as commuter causeways have now rurned into stagnating pools, where hordes of returning parents, bellies distended with food for their insatiable young, splash along hurriedly in the warm evening.
For a moment, at least, summer has arrived. The black-and-white birds splattering mint-green, nitrate-enriched algal goo as they run; tufty golden clouds hanging in a windless blue sky; the chocolate-hued volcanic strata and pink-painted guano slopes reflected in still puddles these images conspire to create as colourful and idyllic a scene as Antarctica can muster.
On arrival at the colony, each adult calls out his or her own chicks from the dense crowd of fluffy grey offspring, parent and chicks recognising each other by voice. Everywhere the energetic youngsters give their parents a merry chase, stumbling and squealing with anticipation. There is a happy, contented mood; fat chicks getting fatter in preparation for the big departure, the biological clock of the Adèlies ticking right on time.
My final Cape Adare visit of the season takes place three weeks later. And what a contrast awaits. The first snows of winter already dust the land, while the nesting plain that was so covered in birds last time now shows only endless strings of penguins waddling to the sea in one great exodus. Nearly fully grown, and 70 per cent of their parents’ weight, the chicks have shed most of their down, just a few comical tufts clinging to their handsome new plumage.
At the shore, juveniles run up and down the beach as if building up courage to launch themselves into the surf that thunders on to the gravel now that no pack ice remains to dampen the swell. In droves, they clamber on to stranded slabs of overhanging ice, from where they plunge feet first into the ocean.
It takes them some minutes to coordinate their wildly flapping flippers and get used to their new medium, splashing about ineffectively and ducking under for brief dives while they learn. The adult penguins do not wait, but shoot away toward the open ocean, mission accomplished.
No longer in families but all bound for the sea ice soon to reform offshore, the Adèlie penguins will spend the winter in a realm we can barely imagine. For the next seven months they will most probably keep out of sight of land, sleeping and moulting on the ice, swimming and diving at a steady 8 km/h, and porpoising through open leads in bursts of up to 25 km/h to evade leopard seal attacks.
They may travel as far as 1400 km from the nesting ground through the sunless winter. Many will centre their feeding along the edge of the continental shelf, where upwelling is strongest and nutrients most concentrated, diving to depths of up to 170 m. For the young ones, with a life expectancy of 10 to 20 years if they make it through to adulthood, these wanderings may last as long as five years before they return to land for the first time to begin raising their own families.
By the tens of thousands I watch them disappear into the gathering autumn dusk. As I walk away, the eerie silence that has replaced the departed colony’s din is broken only by the pathetic calls of a few frightened, doomed runts. I cannot help but sense the despair of these chicks, too young or too weak to leave. Perhaps orphaned by a leopard seal, or the products of first-time, inexperienced parents, they are condemned to be skua fodder.
The delicate, flattened carcasses of casualties from previous seasons lie mummified and embedded in the freezing ground, soon to be shrouded by winter’s snows. Across the monochrome landscape, desolation reigns. Even the black lava faces curtained off by snow have lost their warm colours.
Yet turning to the sea I feel my heart soar with exhilaration as I witness the magic of a new generation of these extraordinary little penguins coming into its own. All round Antarctica at this very moment scenes like this one are being played out, as an estimated five million Adèlies, plus untold young, leave the land to live on the frozen skin of the sea, their true home.