(完整版)BBC生命第五集

第五集：鸟类

1.5亿年前One 150 million years ago

就在恐龙达到它们繁盛时期时as dinosaurs approached their golden age

有一类生物却朝着一个全新的方向演化one group evolved along new and revolutionary lines. 尽管仍然保留着某些爬行动物的特征Although they retained many of their reptilian characteristics

但它们已经具备全新的they acquired extraordinary new ones...

羽毛..feathers.

羽毛帮助保温、隔热Feathers helped with insulation

展示（鸟类都爱秀）and display.

但羽毛能提供更有价值的东西But they offered something far more valuable.

飞翔的力量The power of flight.

对鸟来说，这改变了一切And for birds

鸟类在空中享有自由，比其它任何动物都跑得更快、更远Birds have the freedom of the skies 能在地球每一个角落获得机会and to seize opportunities in all corners of the planet.

但鸟类也必须在生命中的一些关键时刻But this freedom brings many survival challenges

应付由这种自由带来的生存挑战which birds must tackle at pivotal moments in their lives.

飞翔需要极高的技巧和力量Flying demands enormous skill and effort

秘鲁安第斯山麓，没哪里比在这里更明显了and nowhere is that more evident than here

这只雌性蜂鸟能在吸食花蜜时，稳稳地悬停在空中This female hummingbird hovers with precision in her quest for nectar.

它翅膀和尾巴的构造，能让它朝任何方向飞Her wing and tail design allow her to fly in any direction.

但雄性在飞翔时却有问题But the male has a real problem flying.

这是由于And this is why

它被两根超长的尾羽所压，就像绑着两个沉重的盘he's weighed down with two super-long tail feathers

这就是不可思议的凤尾蜂鸟This is the marvellous spatuletail hummingbird.

这两根长羽毛也是它吸引异性的招牌and these are his flags with which to seduce a mate.

来回地舞动它们要花费很多的气力Waving them back and forth takes a lot of effort

即使是在舒适的栖息场所even from the comfort of his perch

但为了赢得她的芳心，它必须一直努力but to win her heart he's got to go up a gear.

必须证明自己是多么善于飞翔，即便这是件苦差He must show her how well he can fly but it's exhausting work.

由于非常辛苦，它只能腾空几秒钟It's so demanding he can only stay airborne for a matter of seconds

然后休息一下before he needs a rest.

它努力想打动她，作出最后一次尝试He's struggling to impress her

由于极度的耗费体力，蜂鸟只进行短暂的爆发式的飞行The extreme effort and energy needed to hover means hummingbirds can only fly in short

但大部分的鸟需要在空中停留很长时间But most birds need to stay airborne for considerably longer

必须找到更为节省体力的方式and must find far more energy-efficient ways to get around.

在埃塞俄比亚的Simien山脉Here in the Simien mountains of Ethiopia

海拔15000英尺的地方at a breathtaking altitude of 15000 feet

生活着一种空中大师lives a supreme aerial maestro.

髭兀鹰The lammergeier.

这头幼鹰乘着从山谷升上来的气流滑翔This youngster glides on air currents rising from the mountain slopes below.

它长达9英尺的翼展，能带它每天飞行几百英里His nine-foot wingspan can carry him hundreds of miles a day

寻找动物的尸体，却花费极少的力气in search of animal carcasses

它警惕着其它的空中拾荒者，如这只狮鹫He watches out for other airborne scavengers

它们与它在悬崖上造成了一些混乱，或许是个进食的机会They lead him to some commotion on the cliffs

但这头幼鹰并非唯一发现这个机会的But this youngster is not the only lammergeier to spot the opportunity.

这头成年鹰也有份So too has this adult.

秃鹫们很快将尸体吃光了The vultures quickly strip the carcass clean.

看起来它太晚了，实际上抵达时间刚好It seems he's too late. But in fact he's timed his arrival perfectly.

一丁点儿肉都不剩There's no meat left

这正是髭兀鹰所期待的时刻and that's exactly the moment that the lammergeier has been waiting for.

它图的是那些骨头It's bones he's after.

年幼的髭兀鹰也来到这具尸体The young lammergeier too homes in on the carcass.

骨头富含骨髓和油脂Bones contain rich marrow fat

但要得到它们并不容易but extracting it is not easy

尤其是骨头重达4公斤，很坚硬，无法吞下especially when the bone is a solid four kilos and too big to swallow.

但是髭兀鹰有一种奇特的方法，这多亏它们的飞行技能But lammergeiers have an extraordinary solution

将骨头抓起，乘着热气流飞起来Soaring up on thermal air currents and positioning the bone parallel

它很快就爬到了一个完美的高度to his body to minimize drag

从这里滑翔至一个合适的地方From here he glides to a place he knows

让它可以处理骨头where he can deal with the bone

那里悬崖边上，有一块巨大的石板where there are giant rock slabs sit on the lip of an escarpment.

骨头撞碎了The bone is smashed.

它的胃液酸性比蓄电池里的液体还要高The juices in his stomach are more corrosive than battery acid.

能够溶解骨头，以便消化吸收骨髓They dissolve the bone so that he can now digest the marrow.

其它的则过来寻找剩下的Others come looking for leftovers.

但它们时机不好But their timing isn't ideal

因为现在轮到幼年髭兀鹰了because now the young lammergeier has his turn!