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How do birds fly? Why can’t humans fly?

Donna Coutts, October 11, 2020 6:45PM Kids News

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Wedge tail eagle Reggie at Taronga Zoo, NSW. Picture: Toby Zerna media_cameraWedge tail eagle Reggie at Taronga Zoo, NSW. Picture: Toby Zerna

explainers

Reading level: orange

It’s spring and that means lots of busy bird parents nesting, laying eggs and fussing over baby birds, sometimes swooping if you get too close.

Next comes baby birds learning to fly. Sometimes they look so awkward we wonder how they get it right. But give them a few goes and they do!

Taronga Zoo welcomes Griffin the Sooty Owl Chick media_cameraGriffin the sooty owl chick, born at Taronga Zoo, NSW in 2015 and not ready to fly. At only eight weeks old, however, he was fully feathered and ready to fly.

Kids News wondered how birds fly. Why doesn’t gravity pull them down to Earth? And why can they fly and we can’t? Here’s what we learned.

BODIES BUILT FOR FLYING

Most birds have:

Light, hollow bones filled with pockets of air between thin cross pieces for strength;

A beak instead of heavy jaws, teeth and nose;

A rigid* skeleton, good for attaching strong muscles to;

A large breastbone — called a sternum — to which strong chest muscles are attached. They use these muscles to flap their wings;

A streamlined body shape with most of the weight at the centre, rather than the sides, back and front;

Lightweight, smooth feathers that reduce drag, like a fast cyclist wearing Lycra clothes rather than bulky, heavy clothes that flap about in the wind; and

Wings (more on these below).

Lilac-breasted roller media_cameraAn African bird called a lilac-breasted roller showing off its lightweight, smooth feathers and clever wing design. Picture: istock

LIFT OFF!

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 counteract* the downforce of gravity with an upward force called lift. Birds make this force by moving their wings through the air with the front part of its wing slightly higher than the back part.

The air moves faster over the top of the wing; slower under the wing. When air moves faster, the pressure of the air decreases, 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 creates 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 underneath.

media_cameraQantas Airways Airbus A380. Aeroplane wings are shaped to make air move faster over the top of the wing than the bottom.

TYPES OF FLIGHT

Birds use a combination of flying methods according to their size, shape and strength and how and where they live.

  • Flapping: an up and down motion to move the bird up and forward. Pushing the wings down creates lift; the bird partly folds its wings in when it moves them upwards to get into place for the next downward movement.
  • Gliding: the bird just has to hold its wings out and the air flowing around them does the rest, no flapping required.
  • Soaring: a special kind of gliding that makes use of a current of rising air (called a thermal). Birds that fly high over long distances use thermals.

EVERY BIRD IS DIFFERENT

Each bird species has a slightly different wing design to suit its body shape, weight and how it needs to fly.

Some heavy birds — such as pelicans — 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), giving the lift they need, for instance by sitting on a hot rock for takeoff rather than cooler grass.

media_cameraEvery bird species is different. Pelicans are so heavy they sometimes run a bit to take off.

FLIGHTLESS BIRDS

There are around 60 living species of flightless birds including emus, cassowarys, ostriches, kiwis and penguins. Some are great runners (ostriches and emus), can kick to defend themselves (cassowarys, ostriches and emus) or are super swimmers (penguins), so they don’t need to fly to survive. Scientists aren’t sure why kiwis can’t fly but believe they probably once did to reach New Zealand.

COULD A HUMAN FLY?

Humans have been wishing they could fly and trying to make it happen for at least hundreds of years.

Artist, inventor and scientist Leonardo da Vinci, who lived in the 1400s and 1500s in what is now Italy, is one who worked hard on a solution.

He bought birds, studied their bodies and drew designs for a glider with wings that a person could flap. He also designed a type of helicopter.

500 year old drawings of a flying machine by artist Leonardo da Vinci. drawing sketch media_camera500-year-old drawings of a flying machine by Leonardo da Vinci.

Humans’ arms and chest aren’t strong enough to flap wings that would be big enough to hold us up in the air.

Our legs, however, are strong enough: there have been many short flights in leg-powered flying machines through history. The longest was in 1988 when a flying craft called Daedalus flew for three hours, four minutes and 59 seconds over the Greek island of Crete, powered by the pedalling of Olympic cyclist Kanellos Kanellopoulos.

GLOSSARY

  • rigid: does not flex or bend
  • counteract: act against something in order to reduce its force

EXTRA READING

Green flying dude is king of the sky

Big bird flies without flapping

Flying man with jetpack wows Sydney crowds

VR helps cure fear of flying

Feathered frenzy comes to town

QUICK QUIZ

  1. What is the downward force on Earth called?
  2. Describe the three types of flying.
  3. What are penguins good at instead of flying?
  4. Who was Leonardo da Vinci?
  5. How was Daedalus powered?

LISTEN TO THIS STORY

CLASSROOM ACTIVITIES
1. Birds versus Humans
After reading the Kids News article on how birds fly, compare the features of a bird versus the features of a human that might help you explain why humans can’t fly (yet anyway!)

Include details on how they are made, their different bodies and how they both move.

Use a table like this to help you compare birds and humans. media_cameraUse a table like this to help you compare birds and humans.

Time: allow 15 minutes to complete this activity
Curriculum Links: English, Science, Critical and creative thinking

2. Extension
Work with a partner to design and sketch a contraption that you think might help humans fly. Label your contraption and if you have time make a 3D model of it. Be ready to explain to others how and why you think your design could help humans fly.

Time: allow 30 minutes to complete this activity
Curriculum Links: English, Design and Technologies, Critical and creative thinking

VCOP ACTIVITY
I Spy Nouns
Nouns are places, names (of people and objects), and time (months or days of the week).

How many nouns can you find in the article?

Can you sort them into places, names and time?

Pick three nouns and add an adjective (describing word) to the nouns.

HAVE YOUR SAY: What sort of bird would you choose to be? Why?
No one-word answers. Use full sentences to explain your thinking. No comments will be published until approved by editors.

Extra Reading in explainers