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Other creatures benefit from the whales' industry-sea birds forage in their wake.
As the whales drive the krill closer to the surface, it comes within reach of birds that are not particularly skilled in diving.
Cape Petrels, about the size of pigeons, can only duck dive a few feet down. But that is enough to give them a share.
360 million sea birds constantly scour the southern ocean for food. They only go to land to breed. Most of their lives are spent on the wing far out at sea.
This ocean is rich in nutrients and very rough. Howling gales whip it into huge waves. These, with so few islands to interrupt and break them, grow and grow into some of the most mountainous seas to be found in any ocean.
Birds dispersed over its vast surface face a huge problem in finding food, for it is by no means uniformly spread throughout the ocean. The nutrients occur in patches, and so the krill, which is sustained by those nutrients, is patchy too. But once the birds find a swarm, there is a frenzy of feeding.
Krill typically spends the day in deep water, rising nearer to the surface at night. But sometimes, a swarm rises during the day and then the birds get their chance. But getting to the krill is still a major problem to all birds except penguins. Albatrosses such as the black-browed whose diet is about 40% krill can only dive down a couple of meters at the most.
New Words & Phrases
forage:草料
Howling:Marked by the sound of howling:
嚎叫的，咆哮的，怒号的：
a howling wind.
怒号的风
by no means :In no sense; certainly not:并没有；绝不
This remark by no means should be taken lightly.
这次讲话绝不能等闲视之
patch:A small piece, part, or section, especially that which differs from or contrasts with the whole:
小片，一小部分
Albatross:信天翁
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