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第一段
1 .Scientists believe that a majority of the earth’s bird population migrate in some fashion or other.
科学家认为，地球上的大多数鸟类都以这样或那样的方式迁徙。
2 .Some travel seasonally for relatively short distances, such as birds that move from their winter habitats in lowlands to mountain tops for the summers.
有些是季节性迁徙，距离相对较短，比如鸟类从它们冬季的低地栖息地迁徙到夏季的山顶。
3 .Others, like the Arctic Tern, travel more than 25,000 miles seasonally between the northern and southern poles.
其他的，比如北极燕鸥，季节性地在南北两极之间旅行超过25000英里。
4 .Bird migration has been studied over many centuries through a variety of observations.
几个世纪以来，人们通过各种观察对鸟类迁徙进行了研究。
5 .But until relatively recently, where birds went to in the winter was considered something of a mystery.
但直到最近，鸟类在冬天去哪里还被认为是一个谜。
6 .The lack of modern science and technology led to many theories that we now recognize as error-filled and even somewhat amusing.
现代科学技术的缺乏导致了许多我们现在认为充满错误甚至有些可笑的理论的存在。
7 .Take hibernation theory for example – two thousand years ago, it was commonly believed that when birds left an area, they went underwater to hibernate in the seas and oceans.
以冬眠理论为例，两千年前人们普遍相信，当鸟儿离开一个区域，它们会在海洋里冬眠。
8 .Another theory for the regular appearance and disappearance of birds was that they spent winter hidden in mud till the weather changed and food became abundant again.
关于鸟儿有规律的出现或消失，还有另一个理论：鸟儿会藏在泥里过冬，直到天气变暖且食物再次变得充裕。
9 .The theory that some birds hibernate persisted until experiments were done on caged birds in the 1940s which demonstrated that birds have no hibernation instinct.
鸟类冬眠的理论一直存在，直到20世纪40年代在笼子里做的实验证明鸟类没有冬眠的本能。
10 .One of the earliest naturalists and philosophers from ancient Greece was Aristotle who was the first writer to discuss the disappearance and reappearance of some bird species at certain times of year.
古希腊最早的博物学家和哲学家之一是亚里士多德，他是第一个讨论一些鸟类在一年中的特定时间消失和重新出现的作家。
11 .He developed the theory of transmutation, the seasonal change of one species into another, by observing redstarts and robins.
亚里士多德通过观察红尾鸲和知更鸟，提出了演变理论，认为这些鸟会季节性地转换成其他物种。
12 .He observed that in the autumn, small birds called ‘redstarts’ began to lose their feathers, which convinced Aristotle that they changed into robins for the winter, and back into redstarts in the summer.
这让亚里士多德相信这种鸟儿在冬天的时候会变成知更鸟，在夏天时则会变回来。
13 .These assumptions are understandable given that this pair of species are similar in shape, but are a classic example of an incorrect interpretation based on correct observations.
鉴于这一组鸟类在体型上接近，所以这些假设可以理解。但是，这是基于正确观察得出的错误解读的典型案例。
14 .The most bizarre theory was put forward by an English amateur scientist, Charles Morton, in the seventeenth century.
最奇异的理论是由英国业余科学家查尔斯·莫顿在17世纪提出的。
15 .He wrote a surprisingly well-regarded paper claiming that birds migrate to the moon and back every year.
他写了一篇关于鸟儿每年会迁徙去月球再返回地球的论文。这篇论文大获好评。
16 .He came to this conclusion as the only logical explanation for the total disappearance of some species.
他得出这个结论，认为这是某些物种完全消失的唯一合乎逻辑的解释。
第二段
1 .One of the key moments in the development of migration theory came in 1822 when a white stork was shot in Germany.
迁徙理论发展的关键时刻之一发生在1822年，当时一只白鹳在德国被射杀，这只特殊的鹳创造了历史。
2 .This particular stork made history because of the long spear in its neck which incredibly had not killed it – everyone immediately realised this spear was definitely not European.
一根长矛刺穿了它的脖子却没有杀死它。人们立即意识到这长矛肯定不属于欧洲。
3 .It turned out to be a spear from a tribe in Central Africa.
结果证明，这根矛来自非洲中部的一个部落。
4 .This was a truly defining moment in the history of ornithology because it was the first evidence that storks spend their winters in sub-Saharan Africa.
这是鸟类学研究史上决定性的一刻，因为（人们）第一次持有了鹳在非洲撒哈拉沙漠以南的地区过冬的证据。
5 .You can still see the ‘arrow stork’ in the Zoological Collection of the University of Rostock in Germany.
你仍然可以在德国罗斯托克大学的动物收藏中看到这只“箭鹳”。
6 .People gradually became aware that European birds moved south in autumn and north in summer but didn’t know much about it until the practice of catching birds and putting rings on their legs became established.
人们逐渐意识到，欧洲的鸟儿秋天往南飞，夏天往北飞，但是不甚了解，直到抓取鸟儿后给鸟儿带上脚环变成一种惯例。
7 .Before this, very little information was available about the actual destinations of particular species and how they travelled there.
在此之前，人们并不清楚某一特定物种准确的迁徙目的地，以及它们是如何去到那儿的。
8 .People speculated that larger birds provided a kind of taxi service for smaller birds by carrying them on their backs.
人们推测，体型较大的鸟类为体型较小的鸟类提供了一种出租车服务，它们把体型较小的鸟类背在背上。
9 .This idea came about because it seemed impossible that small birds weighing only a few grams could fly over vast oceans.
这个想法的产生是因为体重只有几克的小鸟似乎不可能飞越浩瀚的海洋。
10 .This idea was supported by observations of bird behaviour such as the harassment of larger birds by smaller birds.
这一观点得到了对鸟类行为的观察的支持，例如大型鸟类受到小型鸟类的骚扰。
11 .The development of bird ringing, by a Danish schoolteacher, Hans Christian Cornelius Mortensen, made many discoveries possible.
由丹麦教师Hans Christian Cornelius Mortensen发起的鸟类环志让许多发现变得可能。
12 .This is still common practice today and relies upon what is known as ‘recovery’ – this is when ringed birds are found dead in the place they have migrated to, and identified.
鸟类环志依然是今天常见的惯例，依赖于找回，即被套上脚环的鸟儿死去之后，人们在它迁居之地找到并且识别它。
13 .Huge amounts of data were gathered in the early part of the twentieth century and for the first time in history people understood where birds actually went to in winter.
在20世纪早期，人们收集了大量的数据，这是历史上第一次，人们了解到了鸟类在冬天到底去了哪里。
14 .In 1931, an atlas was published showing where the most common species of European birds migrated to.
在1931年，一份印有欧洲寻常鸟类迁徙去向何处的地图集出版了。
15 .More recent theories about bird migration …
更多近期关于鸟类迁徙的理论……