David Attenborough's Conquest of the Skies 3D Page #3

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Microscopic structures

within them, suggest that

they had flashes of iridescence.

So these feathers were

probably used for display.

But their asymmetric shape

is characteristic of flight feathers.

The air flowing over the narrow front

of the feather, can produce lift.

So could this strange looking dinosaur

with feathers all over it, actually fly?

Some people think that

those feathers on its hind legs

would have made it rather difficult

for it to walk around on the ground,

and that it would have been

more at home, climbing.

And those claws on the fingers and toes

are obviously very helpful,

in climbing up tree trunks.

But those aerodynamically shaped

feathers certainly suggest

that its arms were been used as wings.

This four-winged dinosaur must have

been a really extraordinary animal.

Its front wings were broad

enough to enable it to glide,

and its muscles on the chest

were sufficiently strong

to enable it to flap every now and then,

and help it on its way.

But the wings on the hind legs

were probably not held spread out,

but kept beneath the body

to help the animal to steer.

Now clearly, these dinosaurs

were on their way

to join the Pterosaurs in the sky.

And then, discovered once again

in the rocks of China,

came creatures that are

recognizable as birds.

This is Confuciusornis.

There are two of them here.

They no longer have

heavy bony jaws studded with teeth.

Instead, they have

short beaks made of horn,

without teeth, lightweight.

And the tail is no longer supported

by a whole chain of small bones.

These bones have been reduced

to this tiny little stump here.

These are true birds.

But the long feathers attached

to the tail of one of these specimens,

can reveal something intriguing

about these early birds.

To find out what they were for,

we can look for a bird here in Borneo

that has very similar tail feathers.

This is the racket-tailed Drongo,

and it's tail feathers bare

an astonishing resemblance,

to those of its distant

ancestor, Confuciusornis.

They don't seem to help

its flight in any way.

So the Drongo must be using them

for something else:

Display.

And so, while the birds continued

to improve their flight,

they also continued to use

their feathers in courtship,

as their dinosaur ancestors

had probably done.

But birds use, not just the shape

of their feathers for display,

but also their colour, and there's

some really lovely examples of that,

here in Borneo.

These birds are colourful enough,

but one is particularly spectacular.

This is the Bornean Peacock-Pheasant.

This is the male. His feathers are emblazoned

with colourful iridescent patterns.

And that's because they're used

to attract the attention of a female.

Her feathers are comparatively drab.

First, the male lures

the female into his courtship arena,

with the promise of food.

A worm.

He begins to shake

his magnificent feathers.

He clears the ground of anything that

might interfere with his performance.

As the female dives in

after the worm, he raises

all of his feathers in a huge fan.

If she approves of his display,

she may choose him as a mate,

over other rival males.

Eventually she makes off

with the offering of food,

and it seems she was not as impressed

as she might have been.

So feathers, so lightweight,

and so easily erected,

can serve as billboards on which

to advertise for a mate,

or warn off rivals.

But to see how the early birds

used their feathers

to achieve fully powered flight,

we are returning to Britain.

Here, on a Loch in Scotland,

we can watch some of the most

majestic flyers around today:

Whooper Swans.

These particular birds were

in contact with human beings

from the very first moment

that they hatched, so they allow me

to get really close to them.

The small feathers on their bodies

are still essential

for keeping their owners warm.

But this one is a wing feather.

It extremely strong, but very light,

and the filaments on either side

of the quill, the barbs,

zip together, to form

a continuous surface which is

strong enough to hold the air.

But if the air is to support

a big bird as it flies,

it has to move over the wing very fast.

And in order for that to happen,

these Swans will move at speed

across the surface of the water,

like an aircraft taxiing before take-off.

When you're close up

to a flying bird like this,

you can see how a wonderful piece

of complex engineering their wings are,

able to change their shape and their beat,

to respond to every little change

in the currents of the air around them,

and so propel them forward

and lift them upwards.

So, how do bird wings actually work?

If we slow them down, we can watch

in detail the many subtle changes

they make, as they move up and down.

The feathers overlap to form

a smooth, contoured surface

that extends far beyond the bones within.

With a curved leading edge at the front,

and a sharp trailing edge at the back,

they have the classic aerodynamic

shape, that produces lift.

They are aerofoils.

With each downward beat,

the air pressure above is reduced,

so that the bird is sucked upwards.

Wings like these, consisting

of jointed bones covered

with closely fitting feathers,

can make very subtle, delicate movements.

The feathers slide over one another,

so that when the wing changes shape,

there is no loss of smoothness

on the contour.

When the swan slightly retracts

its wings in between beats,

the sliding feathers ensure

that the aerofoil still produces lift.

As well as lightweight beaks

and shortened tails,

some of the bones of its body

have become hollow.

The result is an extremely efficient,

light-weight flyer.

We are traveling around

30 miles an hour now,

and yet these birds

could easily accelerate,

and leave us behind if they wanted to.

So feathers, since they're first appearance

on the bodies of dinosaurs,

have acquired several

different functions.

Initially, they served

to keep their owners warm.

Then, some grew large

and acquired colour, and

were probably used in courtship displays.

And only then, after millions of years,

were they used to help

their owners get into the air.

So around 150 million years ago,

birds joined the Pterosaurs

and insects in the skies.

Then, around 66 million years ago,

came the global catastrophe

that triggered the disappearance

of a vast proportion

of the animal life of this planet.

An asteroid hitting the Earth,

was the most likely cause

of this mass extinction.

In the devastation that followed,

the dominant creatures of that age,

the dinosaurs, disappeared.

The Pterosaurs were completely wiped-out.

And only a few of the birds survived.

The skies for a short period,

must have been relatively empty.

But then, a new kind

of flying animal appeared.

Now is a chance for a group

of furry warm-blooded little creatures,

that had been scampering around

the feet of the dinosaurs

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