How Do Birds Fly?鳥兒如何飛翔?

Donna Coutts　周碩

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.

現在是春天，許多忙碌的鳥爸爸、鳥媽媽正在筑巢、下蛋和照顧雛鳥。接下來雛鳥就要學習飛翔了。鳥是怎么飛翔的呢？為什么重力沒有把它們拉到地上？為什么它們能飛而我們人類不能呢？下面是我們了解到的內容：

Bodies Built for Flying

為飛行而生的身體

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.

大多數鳥類有輕而中空的骨頭，里面充滿空氣，增強了力量；有喙，而不是沉重的下顎、牙齒和鼻子；有利于附著強壯肌肉的骨骼，它們用這些肌肉拍打翅膀；流線型身形，大部分重量集中在身體的中心，而不是兩側或者前后；羽毛和翅膀使鳥兒在風中更加輕盈。

Lift Off！

起飛！

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.

輕盈和流線型是很有用的，但這還不足以克服向下的重力使鳥離開地面。鳥類用一種叫作升力的向上力抵消重力的向下力。它們通過在空中移動翅膀來產生這種力，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。

空氣在翅膀上方流動得更快，在翅膀下方速度較慢。當空氣流動得更快時，空氣壓力降低，因此翅膀上方的壓力小于翅膀底部的壓力。空氣沖向壓力較低的區域（就像從氣球中沖出的空氣），產生了一種稱為升力的力，將翅膀和鳥向上推。飛機機翼的形狀也使空氣在機翼上方比在機翼下方流動得更快。

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.

鳥類根據它們個頭的大小、體型和力量以及它們生活的方式和地點使用不同的飛行方式，有振翅、滑翔和翱翔。

Every Bird Is Different.

每只鳥都不一樣。

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.

每種鳥的翅膀略有不同，為了適應其體型、重量和飛行方式。有些體型較重的鳥需要助跑一下才能起飛。其他鳥則喜歡從樹上起飛。其他比較重的鳥類在熱空氣（上升）的幫助下起飛，鳥站在熱石頭上而不是在涼爽的草地上來獲取起飛所需的升力。

Flightless15 Birds

不會飛的鳥

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.

世界上大約有60種不會飛的鳥類，如幾維鳥和企鵝。有些鳥是優秀的跑步者或超級游泳運動員，所以它們不需要靠飛翔尋找食物。科學家們不確定為什么幾維鳥不能飛，但他們猜這些鳥很可能曾經到達過新西蘭。

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.

大約幾百年來，人類一直希望自己能飛，并試圖實現這一目標。但我們的身體不是為飛翔而設計的，于是有人發明了飛機。從那以后，人類可以用不同于鳥類的方式飛行了。

（英語原文選自：kidsnews.com.au）