D. Structures and Mechanisms · Flight

Nature's Flyers: Adaptations for Flight

D2.5 D2.3 A1.1About 45 minutes

Learning goals

I can describe characteristics and adaptations that help birds, bats and insects fly.
I can tell the difference between powered flight and gliding.
I can explain how some plants use the air to spread their seeds.
I can use a research process to find out about a flying organism.

Words to know

adaptation
A feature or behaviour that helps a living thing survive in its environment.

organism
Any living thing: a plant, an animal, a fungus or a tiny one-celled living thing.

powered flight
Flying by flapping wings to make thrust and lift, like birds, bats and insects.

gliding
Moving through the air without making thrust, slowly losing height, like a flying squirrel.

keel
The large ridge on a flying bird's breastbone where its strong flight muscles attach.

membrane
A thin, flexible sheet of skin or tissue.

samara
A seed with a papery wing, like a maple key.

Nature's engineers

Long before people built airplanes, nature was full of flyers: birds, bats, insects, gliding squirrels and even seeds. People studied birds for centuries when they tried to build flying machines.

Today you will find out what adaptations let living things fly, and how each one connects to the four forces: more lift and thrust, less weight and drag.

Three groups of animals with powered flight

Only three groups of animals living today can fly by flapping: birds, bats and insects. Others, like flying squirrels, can only glide.

Birds

Feathers are light and strong. Long flight feathers on the wings make a large surface to push on air. Tail feathers help steer and brake.
Light bones: many of a flying bird's bones are hollow and filled with air, with thin braces inside for strength.
A beak, not teeth: a beak is lighter than a jaw full of teeth.
A big keel on the breastbone holds the large chest muscles that power each wingbeat (thrust and lift).
Streamlined bodies reduce drag.
Special lungs with air sacs take in lots of oxygen for hard-working muscles.

Bats

Bats are the only mammals that can truly fly.
A bat's wing is a thin membrane of skin stretched between very long finger bones, down to its legs. The bat can bend its fingers to change the wing's shape, so it can twist and turn quickly to catch insects at night.

Insects

Insect wings are thin, light and stiff. Many insects, like dragonflies and butterflies, have two pairs of wings.
Flies have one pair of wings plus two tiny knobs that help them balance.
Strong muscles in the middle body part (the thorax) beat the wings very fast.

A dragonfly with four clear, veined wings resting on a green cattail leaf beside a pond. — A dragonfly has four thin, light wings that it can move separately, so it can hover, dart and even fly backward. AI-generated image

Simplified cross-sections, not to scale. Left: a mammal leg bone is mostly solid bone with marrow in the middle. Right: many of a flying bird's bones are hollow and filled with air, with a thin wall and thin bony braces (struts) inside that keep them strong but light.

Gliders and floaters

Northern flying squirrels live in Ontario's forests. A furry skin flap stretches from each front leg to each back leg. When the squirrel leaps and spreads its legs, the flap acts like a wing (lift and drag), and its flat tail helps it steer. It glides from tree to tree but cannot fly upward.
Maple keys (samaras) have a papery wing. As they fall, they spin, which slows the fall so the wind can carry the seeds away from the parent tree, where they have more space and light to grow.
Dandelion seeds hang under a fluffy tuft that works like a parachute (lots of drag for little weight).

Flyer	Flight type	Key adaptations	Which forces they help
Bird (e.g. Canada goose)	powered	feathers, hollow bones, keel and big chest muscles, streamlined body	lift, thrust; less weight and drag
Bat (e.g. little brown bat)	powered	skin membrane on long finger bones; flexible wing shape	lift, thrust; quick control
Insect (e.g. dragonfly)	powered	thin light wings, fast wing muscles, often two pairs of wings	lift, thrust; quick control
Northern flying squirrel	gliding	furry skin flap between front and back legs; flat tail	lift and drag (no thrust)
Maple key	spinning fall	papery wing that spins	drag and lift slow its fall

Flyers in nature

Wing shapes match the job

Long, narrow wings (like a gull's) are great for gliding and soaring over open water with little flapping.
Broad wings with spread-out tip feathers (like a red-tailed hawk's) are good for soaring in circles on rising warm air.
Short, rounded wings (like a ruffed grouse's) give fast, powerful takeoffs and quick turns between trees.
Tiny, fast wings (like a hummingbird's) can hover and even fly backward.

The shape of a wing matches the job. Long, narrow wings are best for gliding, broad wings with spread tip feathers for soaring on warm air, and short, rounded wings for quick takeoffs and turns.

Worked example

Let's compare a bird wing and a bat wing

How are a bird's wing and a bat's wing alike and different?

Alike: both are front limbs (arms) that became wings. Both push air down and back to make lift and thrust.
Different (surface): a bird's flying surface is made of feathers. A bat's is a skin membrane.
Different (bones): a bat has very long finger bones that hold the membrane open. A bird's wing has fewer, joined finger bones, and the feathers make most of the wing.
What it means: a bat can bend its fingers to change wing shape very quickly, which helps it turn sharply to catch insects.

Both are arms used as wings to make lift and thrust. A bird's wing is made of feathers; a bat's is skin stretched over long finger bones.

Worked example

Let's explain an adaptation with forces

Why does it help a flying bird to have hollow bones and a beak instead of teeth?

Flying birds must make enough lift to hold up their weight.
Hollow bones and a toothless beak make the bird lighter.
With less weight, the bird needs less lift and less effort (thrust from flapping) to fly.

They reduce weight, so the bird needs less lift and less energy to fly.

Just for fun

Why do Canada geese fly south for the winter?

Because it is much too far to walk!

Hands-on activity

Feather study and flyer fact card

Part A: feather study. You need: a craft-store feather (or a feather from an old feather pillow) and a magnifying glass if you have one. (Don't pick up feathers or touch dead birds outdoors: they can carry germs.)

Find the shaft (the stiff centre) and the vanes (the flat parts on each side).
Look closely: the vanes are made of tiny barbs. Gently pull two barbs apart to make a gap.
Now stroke the vane from the shaft outward between your finger and thumb. The barbs "zip" back together, because tiny hooks hold them.
Wave the feather. Then wave a piece of paper the same size. Which feels lighter?

Part B: research (A1.1). Choose one flying organism that lives in Ontario (a monarch butterfly, a little brown bat, a red-tailed hawk, a dragonfly, a Canada goose, a northern flying squirrel or a sugar maple's seeds). Find two reliable sources (a library book, a provincial or federal government site, a nature centre or museum site). Make a fact card that answers:

Does it use powered flight, gliding or the wind?
Two adaptations that help it fly, and which force each one helps.
One question you still wonder about.

Write the names of your sources on the back.

What to look for: Part A: the barbs zip together; the feather is light but stiff. Part B: correct flight type, two adaptations linked to a force (e.g. "hollow bones: less weight"), and two named sources.

Your turn

Name the three groups of animals living today that can fly by flapping.

Give two adaptations that help birds fly.

What is a bat's wing made of?

What is the difference between powered flight and gliding?

How does a northern flying squirrel glide?

How does a maple key's shape help the tree?

Why do flying birds have big chest muscles?

More practice: warm-up

True or false: bats are mammals.

True or false: flying squirrels can flap and fly upward.

What part of a bird helps it steer and brake?

Which seed uses a fluffy tuft like a parachute?

What is the ridge on a bird's breastbone called?

More practice: on your own

Explain how hollow bones help a bird with the four forces.

A gull has long, narrow wings. A ruffed grouse has short, rounded wings. Match each to a way of flying.

Why do you think bats' flexible wings are useful for hunting insects at night?

How is a dandelion seed like a parachute?

A hummingbird can hover. Which adaptation helps, and what must be true about its forces?

Challenge

Some birds, like ostriches, can't fly. Their bones are heavier and their keel is small or missing. Use the four forces to explain why these features don't stop them from surviving.

Engineers sometimes copy nature (this is called biomimicry). Give one example of a plane feature that is like a bird adaptation.

A student says, "A maple key flies like a bird." Is this accurate? Explain with the four forces.

Check your understanding

Quiz

Which animals living today can fly by flapping?

How do hollow bones help a bird fly?

A bat's wing is made of:

A northern flying squirrel:

Why does a maple key spin as it falls?

What is the keel on a bird's breastbone for?

For parents and teachers

Big idea (D2.5): birds, bats and insects have adaptations for powered flight (light bodies, wing surfaces of feathers, skin or thin wing material, strong flight muscles); others glide (northern flying squirrels) or use the wind (maple keys, dandelion seeds). Each adaptation can be linked to one of the four forces.

Research (A1.1): help your child choose reliable sources: library books, museum or nature centre websites, and government wildlife pages. Ask "Who wrote this? How do they know?"

How to help: go on a walk and watch for flyers: gulls soaring, crows flapping, maple keys spinning. Ask "Powered or gliding? How can you tell?"

Common difficulties:

Thinking flying squirrels fly. They glide only.
Thinking all bird bones are hollow. Many are, especially in flying birds, but not every bone, and some birds (like loons, which dive) have heavier bones.
Safety: do not handle wild feathers, dead birds or bats (bats should never be touched: call local wildlife or public health if one is found indoors). Use a craft-store or pillow feather.