PLANET EARTH Ice Worlds
These are noon attacks the exposed peaks of vast mountain ranges buried in ice over a mile deep. The eerie（可怕的） silence here is only broken in spring. The snow petrels（雪燕） have arrived and are courting. Antarctic petrels now join the most southerly colony on Earth. The birds have flown inland for over three hundred miles to reach this breeding site. Once their eggs have hatched they'll be forced repeatedly to make the 600 mile round trip to gather food in the ocean.
First though valuable nesting places must be defended from property thieves. After laying their eggs the petrels take time out to clean their plumage（羽毛）. The south polar skua（贼鸥） is a formidable（难以对付的） opportunist（机会主义者） but the skuas have not chanced upon the petrels they've been waiting for them. These birds do not need to go to the ocean for their food. The skuas can survive further south than any other predator by exploiting the petrels' desperate need for bare rock.
Even at the height of summer less than 3% of Antarctica is free of ice and nearly all of that exposed rock is found in one place the Antarctic Peninsula（半岛）. It's long arm extends further north than the rest of the continent, so spring arrives here first. The thaw unlocks sheltered bays that provide refuge（避难所） from the relentless battering of the southern ocean.
