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科学美国人60秒:鸟类实际上是如何飞行的?

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

这里是《科学美国人》的60秒科学,我是艾米丽·施温。

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

你是否有过这样的经历,抬头看到一只在头顶翱翔的鹰,或者是一只飞过的小山雀,然后想:它们是怎么做到的?

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

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.

塔里亚·洛伊·梅里:我研究了形式和功能之间的最基本的关系。

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 projection from the middle called the keel, and this is where the flight muscles are attached.

塔里亚·洛伊·梅里是加拿大多伦多大学的博士生。她说鸟类飞行与鸟类胸骨的形状和大小有关。鸟的胸骨从中间有一个突起,叫做龙骨突,是飞行肌肉附着的地方。

Lowi-Merri: It's plausible 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.

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相对于身体有这么大的差异呢?关于它的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 lark, 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,梅里开始用CT扫描105种不同鸟类胸骨的数据库寻找答案,这些鸟类包括红顶云雀、利奇风暴海燕和南方食火鸡。她还收录了两种已经灭绝的鸟类:渡渡鸟和大海雀。这种扫描结合了一系列x射线来生成三维图像。

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 projections about the middle and its sides. Looking at it in three dimensions is the best way to quantify the shape and analyze it in a statistical 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.

洛伊·梅里: 最近出现了一些新的技术可以用来更好的观察三维形状。因为胸骨在三维空间中是一个复杂的元素,它不仅仅是一个二维的骨头,它的中间和侧面都有突起。在三维空间中观察是量化形状和在统计框架中分析它的最好方法。所以最近,这些方法变得更容易使用。我想正是因为这样,我现在才有能力做这件事,而在10年或15年前,这是不可能的。

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

梅里及其同事使用这些扫描结果创建了计算机化的 3D 模型。

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 landmarks, and the landmarks basically quantify in 3-D computer space where the important points are on the element.

洛伊·梅里: 有了3D模型,我们就可以移动它。可以在重要位置上放点。这就是我正在做的。我把这些点称为界标,界标基本上在 3-D 计算机空间中量化,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 locomotion in birds]

发表在 BMC Biology 上的研究结果表明,胸骨的大小和形状对鸟类的飞行方式有直接影响。[Talia M. 洛伊·梅里等人,鸟类胸骨变异与运动方式的关系]

[Sound of an eagle]

[鹰的声音]

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.

洛伊·梅里: 所以老鹰在翱翔时,不会频繁地挥动翅膀。它只是伸出双臂,在翅膀和肩部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量。

But compare the majestic eagle with a frantically flapping duck…

但是将雄鹰与疯狂拍打的鸭子进行比较……

[Sound of ducks flying]

【鸭子飞翔的声音】

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 cormorant, the loon and the grebe.

胸骨较深的鸟飞得较慢,胸骨较长的鸟与奔跑有关。梅里还研究了脚踏式水下潜水鸟。这些是鸬鹚、潜鸟和鸊鷉等物种。

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

洛伊·梅里:他们的胸骨是流线型,胸骨龙骨较低,整体紧凑而扁平的,但我们实际上在翅膀推进潜水的鸟类中看到了一些非常相似的东西。

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

那些用翅膀推进的潜水鸟,包括在海洋中发现的小型鸟类——海雀、普通海鸥和企鹅。梅里说,无论是翼式还是脚踏式,这些鸟的胸骨形状相似。

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)

不仅是运动,所有其他的因素都可能成为影响胸骨形状的最大因素,比如鸟类会跳舞以吸引配偶,或者它们的蛋相对于它们的体型有多大。我们只是触及了表面,研究了变异的一个方面,还有更多东西需要探究。”

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单个物种的不同资源需求。

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

深入研究今天的鸟类是如何飞行的,可以告诉科学家很多关于它们在数百万年里的进化信息。

Lowi-Merri: So, birds evolved from dinosaurs… 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.

洛伊·梅里:所以,鸟类是从恐龙进化而来的,我们并不确切地知道哪些鸟类化石和哪些恐龙能够飞行。但是,更好地了解今天的鸟类是如何飞行的,是完成恐龙进化的关键一帧。

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

梅里计划接下来深入研究鸟类化石,部分原因是为了更多地了解飞行的起源。

Lowi-Merri: The thing about fossil birds is that a lot of them are flattened into rock slabs. 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: 鸟类化石的问题在于,它们很多都被压成了岩石板。但是有这么多令人惊叹的鸟类化石,尤其是来自中国的…… 因此,它们的研究必须稍有不同,因为它们可能无法像对现代鸟类胸骨所做的那样,将它们置于 3D 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.

但现在,梅里说,她对那些从她窗前飞过、在她安大略省后院的树枝上占主导地位的雀形目小鸟有不同的看法。

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 predators 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 metabolism 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,拍打的频率很高,从一个枝头移动到另一个枝头。它们试图远离捕食者并获取一些食物,无论是昆虫还是浆果。我开始思考它们的骨骼是如何构造的,以及他们的肌肉是如何运作的,比方说,这与上面翱翔的鹰有何不同。因此,它们需要不同的新陈代谢和不同的食物来源,而它们在体内的使用方式也会大不相同。

[Bird wing flapping]

[鸟翼拍打的声音]

For 60-Second Science, I’m Emily Schwing.

以上是今天的60秒科学,艾米丽·施温报道。

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

Have you ever looked up to see a hawk 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.

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 projection from the middle called the keel, and this is where the flight muscles are attached.

Lowi-Merri: It's plausible 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.

So, Merri set out to find some answers using a database of CT scanned sternums from 105 different bird species, like the Red-capped lark, 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.

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 projections about the middle and its sides. Looking at it in three dimensions is the best way to quantify the shape and analyze it in a statistical 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.

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 landmarks, and the landmarks basically quantify in 3-D computer space where the important points are on the element.

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 locomotion in birds]

[Sound of an eagle]

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 majestic eagle with a frantically flapping duck…

[Sound of ducks flying]

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 cormorant, the loon and the grebe.

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

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

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)

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.

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

Lowi-Merri: So, birds evolved from dinosaurs… 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.

Lowi-Merri: The thing about fossil birds is that a lot of them are flattened into rock slabs. 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.

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.

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 predators 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 metabolism and different food sources and how they use that in their body would be very different.

[Bird wing flapping]

For 60-Second Science, I’m Emily Schwing.


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