Antarctica by Gabrielle Walker Page B

fat when they first arrive, having stocked up on fish for the season. As soon as she has laid her eggs the female heads back to open water to replenish, and the male incubates the eggs and keeps the skuas at bay. If he’s lucky, she’ll be back within two weeks to relieve him.
    For the first few weeks after hatching, at least one parent will stay with the chick. But when the chicks are bigger and more demanding, both parents will go off to feed at the same time, saving some fish for themselves and regurgitating the rest into their offsprings’ gaping gullets. By now, the chicks will probably be in a crèche, kept safe by adults that are hanging around or still tending nests. When they are seven or eight weeks old the chicks will lose their soft brown down to reveal a grown-up blue and white penguin suit that will soon turn black. From the first week of February they will head for the sea and be on their own.
    Released from their duties, the parents will feed voraciously for a few weeks to regain their fat reserves. Then they will haul out on sea ice floes and moult. This is apparently the one time these little penguins do not smile. David told me that when they’re moulting they don’t like to be touched. They just sit there, he said, scowling, wanting no other penguins anywhere near, until they have lost their old plumage and grown a new one. And then, as the first fingers of winter touch the continent, they will head north. Not too far, though, for they are true Antarcticans. They may retreat a little, to the edge of the open water to wait out the winter, but they never leave the ice. And then, at the start of spring, they return loyally to the exact same nesting spot, to start all over again.
    At least, that was what normally happened. But the past few years had been challenging ones for the Adélies of Ross Island. In March 2000 a massive chunk of the Ross Ice Shelf broke off to create one of the largest icebergs ever seen. Though it subsequently broke into several pieces, the biggest of these—called B15a 2 —still measured more than a hundred miles long, and was larger than the state of Delaware.
    B15a wedged itself across much of the mouth of McMurdo Sound, blocking the route back from the penguins’ winter homes to their summer nesting spots with a giant white cliff. The only options were to turn left and head to the massive colony at Cape Crozier, on Ross Island’s eastern side, or to turn right, double back on yourself for miles, and then round a corner and find the way here to Cape Royds. Crozier was by far the easier route.
    So what did they do? Thanks to the activities of David and his colleagues, many of the penguins in both colonies wore bands on their flippers, marking who they were and where they were born. That turned out to be the perfect opportunity to find out how loyal they really were to their place of birth. And much to David’s surprise the answer was . . . not very. Royds banded birds had been showing up at Cape Bird, thirteen miles away, and even at Cape Crozier, which was forty miles from where they were supposed to be. Very few had gone the opposite way.
    â€˜This has rewritten the book on immigration and emigration,’ said David. ‘Adélies were supposed to be highly philopatric—religiously returning to the colony where they were born. But now we know that their behaviour is much more pliable than we thought.’
    That was great—in a way. But the megaberg brought a darker side, too. The sea ice would normally break up during the summer, but the gigantic cliffs of B15a had encouraged it to stay around. Adélie colonies are usually within a kilometre of open water, to enable the parents to forage for food quickly and easily, since they can swim much faster than they can walk. But thanks to the iceberg, sea ice now stretched farther than we could see.
    And the Adélies were suffering. ‘There are so few birds,’