How Do Birds Fly?鸟儿如何飞翔?

Donna Coutts　周硕

Its spring and lots of busy bird parents nesting， laying eggs and taking care of baby birds. Next comes baby birds leaming to fly. How do birds fly？ Why doesnt gravity1 pull them down to the earth？ And why can they fly and we cant？Here's what we learned.

现在是春天，许多忙碌的鸟爸爸、鸟妈妈正在筑巢、下蛋和照顾雏鸟。接下来雏鸟就要学习飞翔了。鸟是怎么飞翔的呢？为什么重力没有把它们拉到地上？为什么它们能飞而我们人类不能呢？下面是我们了解到的内容：

Bodies Built for Flying

为飞行而生的身体

Most birds have light，hoUoW2 bones filled with air for strength3;a beak4， not heavy jaws5， teeth and nose;a skeleton6 good for attaching7 strong muscles8 to—they use these muscles to flap9 their wings;a streamlined10 body shape withmost of the weight at the centre， rather than the sides， back and front; feathers and wings that make birds much lighter in the wind.

大多数鸟类有轻而中空的骨头，里面充满空气，增强了力量；有喙，而不是沉重的下颚、牙齿和鼻子；有利于附着强壮肌肉的骨骼，它们用这些肌肉拍打翅膀；流线型身形，大部分重量集中在身体的中心，而不是两侧或者前后；羽毛和翅膀使鸟儿在风中更加轻盈。

Lift Off！

起飞！

Being light and streamlined is helpful， but not enough on its own to overcome the downward force of gravity to get a bird off the ground. Birds counteract11 the down force of gravity with an upward force called lift. They make this force by moving their wings through the air. The front part of the wing is little higher than the back part.

轻盈和流线型是很有用的，但这还不足以克服向下的重力使鸟离开地面。鸟类用一种叫作升力的向上力抵消重力的向下力。它们通过在空中移动翅膀来产生这种力，翅膀的前部略高于后部。

The air moves faster over the top of the wing， slower under the wing. When air moves faster， the pressure12 of the air decreases13， so the pressure above the wing is less than the pressure on the bottom of the wing. Air rushes to an area of lower pressure （like air rushing out of a balloon）.This makes the force called lift， pushing the wings and the bird upwards. Aeroplane wings are also shaped to make air move faster over the top of the wing than under it。

空气在翅膀上方流动得更快，在翅膀下方速度较慢。当空气流动得更快时，空气压力降低，因此翅膀上方的压力小于翅膀底部的压力。空气冲向压力较低的区域（就像从气球中冲出的空气），产生了一种称为升力的力，将翅膀和鸟向上推。飞机机翼的形状也使空气在机翼上方比在机翼下方流动得更快。

Birds use different ways to fly according to their size，shape and strength and how and where they live. There are flapping， gliding， and soaring.

鸟类根据它们个头的大小、体型和力量以及它们生活的方式和地点使用不同的飞行方式，有振翅、滑翔和翱翔。

Every Bird Is Different.

每只鸟都不一样。

Each kind of birds has a little different wing design14 to suit its body shape， weight and how it needs to fly. Some heavy birds need to run a bit to get going. Others prefer to take off from up in a tree. Other heavy birds take off with the help of hot air （which rises）. It gives the lift they need by sitting on a hot rock for takeoff rather than cooler grass.

每种鸟的翅膀略有不同，为了适应其体型、重量和飞行方式。有些体型较重的鸟需要助跑一下才能起飞。其他鸟则喜欢从树上起飞。其他比较重的鸟类在热空气（上升）的帮助下起飞，鸟站在热石头上而不是在凉爽的草地上来获取起飞所需的升力。

Flightless15 Birds

不会飞的鸟

There are around 60 kinds of flightless birds， such as kiwis and penguins. Some are great runners or super swimmers， so they dont need to fly to look for food.Scientists aren't sure why kiwis can't fly， but they believe these birds probably once did to reach New Zealand.

世界上大约有60种不会飞的鸟类，如几维鸟和企鹅。有些鸟是优秀的跑步者或超级游泳运动员，所以它们不需要靠飞翔寻找食物。科学家们不确定为什么几维鸟不能飞，但他们猜这些鸟很可能曾经到达过新西兰。

Humans have been wishing they could fly and trying to make it happen for about hundreds of years. But our body is not designed for flying. So airplane was invented. Humans can fly in a different way from birds after that.

大約几百年来，人类一直希望自己能飞，并试图实现这一目标。但我们的身体不是为飞翔而设计的，于是有人发明了飞机。从那以后，人类可以用不同于鸟类的方式飞行了。

（英语原文选自：kidsnews.com.au）