科学美国人60秒 回答一个古老的谜团-鸟类是如何飞行的

Answering an Age-Old Mystery: How Do Birds Actually Fly

回答一个古老的谜团：鸟类是如何飞行的

This is Scientific American’s  60-Second Science, I'm Emily Schwing.

这是《科学美国人》的60秒科学，我是艾米莉·施温。

Have you ever looked up to see a  hawk¹ soar overhead, or a small chickadee flit by and wondered: How do they do that?

Believe it or not, scientists never really knew either?—until now.

你有没有抬头看到一只老鹰在头顶翱翔，或是一只小山雀飞过，你会想：它们是怎么做到的？

信不信由你，科学家们也从未真正知道?—直到现在。

Talia Lowi-Merri: I looked at the relationship between form and function in the most basic sense.

Talia Lowi-Merri is a Ph.D. student at the University of Toronto in Canada. She says bird flight has everything to do with the shape and size of a bird’s sternum, or breastbone. Bird sternums have a projection² from the middle called the keel, and this is where the flight muscles are attached.

Lowi-Merri: It's plausible³ to think that this element is important for flight. But why does it vary so much in shape and size relative to the body? There are all these questions about it that haven't been answered in the past.

塔里亚·洛维·梅里：我从最基本的意义上研究了形式和功能之间的关系。

塔里亚Lui-Meiri是加拿大多伦多大学的博士生。她说鸟类的飞行与鸟类胸骨的形状和大小有关。鸟的胸骨中间有一个突起，叫做龙骨，这是飞行肌肉附着的地方。

洛伊·梅里：认为这个元素对飞行很重要是有道理的。但为什么它的形状和大小与身体有如此大的差异呢？所有这些问题在过去都没有得到回答。

So, Merri set out to find some answers using a database of CT scanned sternums from 105 different bird species, like the Red-capped lark⁴, Leach’s Storm petrel and the Southern cassowary. She also included two extinct birds: the Dodo and the Great auk. The scans combine a series of x-rays to create three dimensional images.

因此，梅里开始利用CT扫描的105种不同鸟类的胸骨数据库寻找答案，比如红顶云雀、利奇的风暴海燕和南方食火鸡。她还包括两种已灭绝的鸟类：渡渡鸟和大海雀。这些扫描结合了一系列的x射线来创建三维图像。

Lowi-Merri: There have been newer technologies come out recently to look at shape in three dimensions. And so because the sternum is a complex element in three dimensions, it's not just a 2-D bone, it's got projections⁵ about the middle and its sides. Looking at it in three dimensions is the best way to quantify the shape and analyze⁶ it in a statistical⁷ framework. So more recently, those methods have become more accessible. And I guess because of that, I was able to do it now and maybe 10 or 15 years ago, it wasn't possible.

Lowi Merri：最近出现了一些新技术，可以从三维角度观察形状。因为胸骨在三维空间是一个复杂的元素，它不仅仅是一块二维的骨头，它的中部和侧面都有投影。从三维角度观察它是量化形状并在统计框架中进行分析的最佳方式。所以最近，这些方法变得更容易使用。我想正因为如此，我现在能够做到，也许在10年或15年前，这是不可能的。

Merri and colleagues used the scans to create computerized 3D models.

Lowi-Merri: And so when you do that, you can move it around. You can place points on it in the important spots. And so that's what I was doing. I was putting these dots that are called landmarks⁸, and the landmarks basically quantify in 3-D computer space where the important points are on the element.

梅里和同事们利用扫描技术创建了计算机化的3D模型。

洛伊·梅里：所以当你这么做的时候，你可以把它移动。你可以在重要的地方放点。这就是我所做的。我把这些点称为地标，地标基本上是在三维计算机空间中量化的，其中重要的点在元素上。

The findings, published in BMC Biology, show that sternum size and shape has a direct impact on the way a bird flies. [Talia M. Lowi-Merri et al., The relationship between sternum variation and mode of locomotion⁹ in birds]

这项研究结果发表在《BMC生物学》上，表明胸骨的大小和形状对鸟类的飞行方式有直接影响。

Lowi-Merri: So an eagle would be soaring and wouldn't be moving its wings as much. It just has its arms stretched out, and it has very intricate structures in its wings and at its shoulder to hold the wings out, but it doesn't have to use as much flapping power.

But compare the majestic¹⁰ eagle with a frantically¹¹ flapping duck…

洛维·梅里：所以一只老鹰会翱翔，不会像以前那样动翅膀。它只需要伸展手臂，翅膀和肩膀上有非常复杂的结构来支撑翅膀，但它不需要使用太多的拍打力。

但是把雄鹰和疯狂拍打的鸭子相比…

Birds with a deep sternal keel fly more slowly, those with long sternums are associated with running birds. Merri also looked at foot-propelled, underwater diving birds. These are species like the cormorant¹², the loon¹³ and the grebe.

胸骨深的鸟飞得更慢，胸骨长的鸟与奔跑的鸟有关。梅里还研究了脚推动的水下潜水鸟类。这些物种包括鸬鹚、龙和灰蝶。

Lowi-Merri: They have this streamlined sternum with lower sternal keels. Everything is kind of compact and flattened¹⁴, but you actually see something really similar in birds that are wing propelled divers¹⁵.

Lowi Merri：他们有流线型胸骨和较低的胸骨龙骨。所有的东西都是紧凑而扁平的，但实际上你在鸟类身上看到了一些非常相似的东西，它们是翅膀驱动的潜水员。

Those wing-propelled divers include small birds you might find on the ocean - puffins, common murres and penguins¹⁶. Merri says whether wing or foot-propelled, the sternums of these birds are similar in shape.

这些由翅膀推动的潜水员包括你在海洋中可能会发现的小鸟——海雀、普通的墨鱼和企鹅。梅里说，无论是用翅膀还是脚推动，这些鸟的胸骨形状都很相似。

All other sorts of factors are possibly most likely contributing to the shape of the sternum, not just locomotion, things like birds that dance to attract a mate or how big their egg is relative to their body size. We've just scratched the surface, looked at one aspect of variation, but there's so much more.” (00:33)

所有其他类型的因素很可能都会影响胸骨的形状，而不仅仅是运动，比如鸟类为了吸引配偶而跳舞，或者它们的卵子相对于它们的体型有多大。我们只是触及了表面，研究了变化的一个方面，但还有更多。”

Merri believes that the shape and structure of the sternum impacts how different species of birds breathe. She also says different methods of flight mean different resource demands for individual species.

梅里认为，胸骨的形状和结构会影响不同种类鸟类的呼吸方式。她还说，不同的飞行方式意味着不同物种对资源的需求不同。

Diving deep into how birds fly today can tell scientists a lot about how they evolved over millions of years.

深入研究鸟类今天的飞行方式可以告诉科学家很多关于它们在数百万年中是如何进化的。

Lowi-Merri: So, birds evolved from dinosaurs¹⁷… and we don't know exactly which fossil birds and which dinosaurs were capable of flight. But, gaining a better understanding of how birds fly today is the key to completing that picture of how the dinosaurs were moving through the world.

Merri plans to dig into fossil birds next, in part to learn more about the origins of flight.

洛伊·梅里：所以，鸟类是从恐龙进化而来的……我们并不确切知道哪些鸟类化石和哪些恐龙能够飞行。但是，更好地了解鸟类今天是如何飞行的，这是完成恐龙如何在世界上移动的图片的关键。

梅里计划下一步深入研究鸟类化石，部分是为了进一步了解飞行的起源。

Lowi-Merri: The thing about fossil birds is that a lot of them are flattened into rock slabs¹⁸. But there are so many amazing bird fossils, especially from China …. And so they will have to be studied a little bit differently because they may not be able to put them in a three dimensional context, as they did with the modern bird sterna.

洛伊·梅里：关于鸟类化石的一点是，它们中的很多都被夷为平地。但是有那么多令人惊叹的鸟类化石，尤其是来自中国…。因此，必须对它们进行稍微不同的研究，因为它们可能无法像现代鸟类胸骨那样，将它们置于三维环境中。

For now, though, Merri says she’s looking differently at the small, passerine birds that flit by her windows and dominate the tree branches in her backyard in Ontario.

不过，梅里说，就目前而言，她对从窗户飞过、在安大略省后院的树枝上占主导地位的雀形目小鸟的看法有所不同。

Lowi-Merri: They're mostly continuous flapping birds. They're flapping pretty quickly. They're moving from branch to branch. They're trying to keep away from predators¹⁹ and get some food, whether it's insects or berries. it made me think about how their skeletons are structured and also how their muscles are working much differently than, let's say, a hawk that's soaring above. And so they would require different metabolism²⁰ and different food sources and how they use that in their body would be very different.

洛伊·梅里：它们大多是连续拍打的鸟类。它们飞得很快。他们从一个分支转移到另一个分支。他们试图远离捕食者，获取一些食物，无论是昆虫还是浆果。这让我想到了它们的骨架是如何构造的，以及它们的肌肉是如何工作的，与在高空翱翔的鹰有很大不同。因此，它们需要不同的新陈代谢和不同的食物来源，它们在体内的使用方式也会非常不同。

1 hawk   

n.鹰，骗子；鹰派成员

参考例句：

• The hawk swooped down on the rabbit and killed it.鹰猛地朝兔子扑下来,并把它杀死。
• The hawk snatched the chicken and flew away.老鹰叼了小鸡就飞走了。

2 projection   

n.发射，计划，突出部分

参考例句：

• Projection takes place with a minimum of awareness or conscious control.投射在最少的知觉或意识控制下发生。
• The projection of increases in number of house-holds is correct.对户数增加的推算是正确的。

3 plausible   

adj.似真实的，似乎有理的，似乎可信的

参考例句：

• His story sounded plausible.他说的那番话似乎是真实的。
• Her story sounded perfectly plausible.她的说辞听起来言之有理。

4 lark   

n.云雀，百灵鸟；n.嬉戏，玩笑；vi.嬉戏

参考例句：

• He thinks it cruel to confine a lark in a cage.他认为把云雀关在笼子里太残忍了。
• She lived in the village with her grandparents as cheerful as a lark.她同祖父母一起住在乡间非常快活。

5 projections   

预测( projection的名词复数 )； 投影； 投掷； 突起物

参考例句：

• Their sales projections are a total thumbsuck. 他们的销售量预测纯属估计。
• The council has revised its projections of funding requirements upwards. 地方议会调高了对资金需求的预测。

6 analyze   

vt.分析，解析 (=analyse)

参考例句：

• We should analyze the cause and effect of this event.我们应该分析这场事变的因果。
• The teacher tried to analyze the cause of our failure.老师设法分析我们失败的原因。

7 statistical   

adj.统计的，统计学的

参考例句：

• He showed the price fluctuations in a statistical table.他用统计表显示价格的波动。
• They're making detailed statistical analysis.他们正在做具体的统计分析。

8 landmarks   

n.陆标( landmark的名词复数 )；目标；（标志重要阶段的）里程碑 ~ (in sth)；有历史意义的建筑物（或遗址）

参考例句：

• The book stands out as one of the notable landmarks in the progress of modern science. 这部著作是现代科学发展史上著名的里程碑之一。 来自《现代汉英综合大词典》
• The baby was one of the big landmarks in our relationship. 孩子的出世是我们俩关系中的一个重要转折点。 来自辞典例句

9 locomotion   

n.运动，移动

参考例句：

• By land,air or sea,birds are masters of locomotion.无论是通过陆地，飞越空中还是穿过海洋，鸟应算是运动能手了。
• Food sources also elicit oriented locomotion and recognition behavior patterns in most insects.食物源也引诱大多数昆虫定向迁移和识别行为。

10 majestic   

adj.雄伟的，壮丽的，庄严的，威严的，崇高的

参考例句：

• In the distance rose the majestic Alps.远处耸立着雄伟的阿尔卑斯山。
• He looks majestic in uniform.他穿上军装显得很威风。

11 frantically   

ad.发狂地, 发疯地

参考例句：

• He dashed frantically across the road. 他疯狂地跑过马路。
• She bid frantically for the old chair. 她发狂地喊出高价要买那把古老的椅子。

12 cormorant   

n.鸬鹚，贪婪的人

参考例句：

• The cormorant is a large,long-necked,dark-colored bird which lives near sea coasts and eats fish.鸬鹚是一种长脖子黑颜色的大鸟，生活在海滨而且以吃鱼为生。
• The exciting cormorant fishing performance is over there.那边有令人刺激的鱼鹰捕鱼表演。

13 loon   

n.狂人

参考例句：

• That guy's a real loon.那个人是个真正的疯子。
• Everyone thought he was a loon.每个人都骂他神经。

14 flattened   

[医]（水）平扁的，弄平的

参考例句：

• She flattened her nose and lips against the window. 她把鼻子和嘴唇紧贴着窗户。
• I flattened myself against the wall to let them pass. 我身体紧靠着墙让他们通过。

15 divers   

adj.不同的；种种的

参考例句：

• He chose divers of them,who were asked to accompany him.他选择他们当中的几个人，要他们和他作伴。
• Two divers work together while a standby diver remains on the surface.两名潜水员协同工作，同时有一名候补潜水员留在水面上。

16 penguins   

n.企鹅( penguin的名词复数 )

参考例句：

• Why can penguins live in cold environment? 为什么企鹅能生活在寒冷的环境中？ 来自《简明英汉词典》
• Whales, seals, penguins, and turtles have flippers. 鲸、海豹，企鹅和海龟均有鳍形肢。 来自《现代英汉综合大词典》

17 dinosaurs   

n.恐龙( dinosaur的名词复数 )；守旧落伍的人，过时落后的东西

参考例句：

• The brontosaurus was one of the largest of all dinosaurs. 雷龙是所有恐龙中最大的一种。 来自《简明英汉词典》
• Dinosaurs have been extinct for millions of years. 恐龙绝种已有几百万年了。 来自《简明英汉词典》

18 slabs   

n.厚板，平板，厚片( slab的名词复数 )；厚胶片

参考例句：

• The patio was made of stone slabs. 这天井是用石板铺砌而成的。 来自《简明英汉词典》
• The slabs of standing stone point roughly toward the invisible notch. 这些矗立的石块，大致指向那个看不见的缺口。 来自辞典例句

19 predators   

n.食肉动物( predator的名词复数 )；奴役他人者（尤指在财务或性关系方面）

参考例句：

• birds and their earthbound predators 鸟和地面上捕食它们的动物
• The eyes of predators are highly sensitive to the slightest movement. 捕食性动物的眼睛能感觉到最细小的动静。 来自《简明英汉词典》

20 metabolism   

n.新陈代谢

参考例句：

• After years of dieting,Carol's metabolism was completely out of whack.经过数年的节食，卡罗尔的新陈代谢完全紊乱了。
• All living matter undergoes a process of metabolism.生物都有新陈代谢。