Original subtitles

We human beings are very latecomers to the skies,

and although we might think that we now pretty good at this,

the Natural World, with the help of several million years of evolution,

has produce a dazzling range of aeronauts whose talents are far beyond our.

The story of how animals manage to colonise the air is truly astonishing.

First into the skies were Insects,

they initially had two pairs of wings

which in due course were modified in many different ways.

But after having had the skies for themselves for about 100 million years,

a new group of animals took to the air,

Vertebrates. creatures with backbones.

They faced a different challenge, for their bodies were much bigger and heavier.

But eventually they evolve several ways of solving that problem.

We will travel the globe to trace the details

of the extraordinary skills of the backbone flyers.

English: Bobiko

~ Conquest Of The Skies ~

- RIVALS -

This is Borneo.

And here there are still great tracks of pristine rainforest.

Forest that is wonderfully rich in animals of all kinds.

I'm being winch up into one of the tallest trees here,

in search of a creature that can give us a hint

of how backbone animals first took to the air.

Hidden among these leafs of this fern, high up here in the canopy,

is a very remarkable little frog.

It's a Harlequin Tree Frog, and it a very-very good climber.

It spend most of its life up here, clumping around in the branches.

Here it's away from the numerous predators there are,

that might attack it down on the forest floor.

But if in fact, a predator were able to get up here, to hunt it,

a snake perhaps, well, the Tree Frog has a remarkable trick for defense.

It glides.

It has membranes between greater elongated toes,

so that each foot becomes a parachute which slow the frog descent,

and so enable it to make a relatively safe landing.

The Vertebrates made their first forage into the air around 260 million years ago,

and it very likely that some of these pioneers use skinny membranes

to control their falls in much the same way as this little frog does.

It has to be said that is not a very good aerial navigator,

it seems that it just jumps and hopes for the best.

But there are animals up here, that glide around from tree to tree,

which are very good navigators indeed,

so good in fact, that they can go from one tree to another

and never go down to the ground in their entire life.

One of them is a little lizard called Draco.

Each male has his own little territory in the branches,

and tries to attract females and warn off rivals by flashing his dewlap.

He also spread colored flaps of skin from his flanks,

that when fully extended do more or less the same thing.

But there are predators among the branches.

Snakes also live up here, and they hunt Lizards.

But Draco side flaps now serve another purpose.

He uses them to glide by hinging forward a specially elongated ribs.

And he so skilled in the air that he can steer land

on the trunk of his choice.

So, if you live up in the branches it's less laborious,

and indeed, safer to travel by air, than to come down to the ground.

But if you want to be a true flyer, you have to be able to fly

not only downwards but upwards, you have to have powered flight.

This is another reptile,

and one with even greater flying abilities than that little gliding lizard.

Today, sadly, it's extinct.

This is Dimorphodon, we can deduce from its fossils

that he had the muscles needed to beat its wings.

And computer imagery can show us what he must was look like.

Dimorphodon was one of the first large animals ever to travel by air,

200 million years ago.

It belong to a group called the Pterosaurs, The Winged Reptiles.

It was probably a forest dweller and it descendant of a tree living glider.

This gliding ancestor might have had wings like those of Draco,

that was made of skin, and perhaps extended from its fingers down to its ankles.

But Pterosaurs have evolved larger wings with a hugely elongated fourth finger.

The wing membrane was strengthen internally by thin rods of a stiffer tissue.

They were muscles fibers too, that enable it to modified its contours as it flew.

Looking at the wings insection revealed a secret of their efficiency.

They have a rounded front edge and a sharp back edge,

a shape known as an aerofoil.

It's works by forcing the air flowing above the wing, to speed up.

This faster air has a lower pressure, and the wing is suck upwards.

The larger the surface area of the wing, the greater lift it can produce.

So, it seem certain that Pterosaurs were very competent flyers.

And judging from their teeth, it's seem likely

that many fed on the great variety of Insects

that had preceded them into the air.

Insects have had the skies to themselves for around 100 million years.

Now, bigger creatures had arrived.

Reptiles.

The Pterosaurs design for flight proved hugely successful,

and before long they had spread out of the forest into new environments.

And some became monstrous.

The first large animals to fly were winged reptiles. Pterosaurs.

They appeared in forests around 220 million years ago.

As they became more successful, they ventured into more open countries

and spread around the world.

A great number of them lived and fed near water.

We know this because fossils of many species

occur in rocks that was once mud at the bottom of lakes and shallow seas.

This one shows the skeleton of little animal that 150 million years ago

fell to the bottom of a shallow lagoon.

This is its head, here is its backbone, tail, hind legs,

and here stretching from these long extended finger bones are its wings.

And this fossil is particularly remarkable,

because it show an impression of the membrane in extraordinary detail.

You can see every little tiny fold.

You can judge how an animal lived by its skull.

And this one, have these long jaws,

with forward pointing teeth, and we think that this indicates

that it lived by skimming across the surface of the lagoon,

and snatching up fish with impaled on those teeth.

The Pterosaurs diversified into a huge variety of forms.

Many seem to been particularly skilled at soaring and gliding

over the oceans, looking for fish.

Some developed huge head crests that were probably colored

and use for display during courtship.

And a few became very big indeed.

This species had a wingspan of over 20 feet, 7 meters.

But not all Pterosaurs lived in the forests or near water.

An open arid landscape like this one, was the likely home

of one of the most extraordinary.

Around 70 million years ago a pterosaur appeared

that was of truly colossal proportions.

That was one of the largest creatures that had ever flown,

it was in the size of a small aeroplane, and it was called Quetzalcoatlus.

Its immense wingspan allowed it to ride on the currents of warm air

that rise up from sun heated land.

It could then glide great distances, searching for food.

Small creatures like lizards, or the dead bodies of much larger ones,

Dinosaurs.

But the Pterosaurs, with their wings of toughen skin

weren't the only group of reptiles to make it into those ancient skies.

About 150 million years ago, another reptilian group appeared

on the Planet that also flew.

Like most reptiles, including Pterosaurs,

these creatures began their lives inside an egg.

But they had evolved a revolutionary new design for flight.

One that would usher in a remarkable fresh chapter in our story.

And unlike the Pterosaurs, they still with us today.

There are of course the Birds.

Some today can provide clues about how their ancestors

manage to get into the air.

This is the chick of a bird found in farmyards everywhere.

A Bantam Hen.

And at this very early stage in its life, it can show us something very interesting

about the origin of that crucial piece of flying equipment.

A feather.

Its feathers are downy, that to say they made up of simple filaments,

and their function is not for flight, but insulation,

to keep this little creature warm.

And back in the Jurassic period, long before the arrival of True Birds,

very similar looking feathers appeared on very different animals.

Reptiles. Dinosaurs if to be precise.

To find evidence for that astonishing statement,

which not so long ago was highly controversial,

we heading for China.

And here, I was able to see the evidence for myself.

Some truly sensational fossils.

Northeast of China Great Wall, near the borders of Mongolia,

lies the chilly province of Liaoning.

Here, there are great areas of rocks that was lay down as mud

in the bottom of immense fresh water lakes.

The bodies of animals that was swept down into these lakes

was slowly entombed by the fine grains sediment

that preserved them entire and in exquisite detail.

And from these rocks have come specimens

that solve one of the most hotly debated of evolutionary arguments.

The origin of the Birds.

The key specimens are now in Beijing,

where they been delicately prepared under the microscope.

They have been studied here by one of the world greatest Dinosaurs experts,

professor Xing Xu.

First, he showed me one of his oldest specimens,

part of a Dinosaur arm.

But thanks to the finest of the mud of those ancient lakes,

there is more here than just bones.

You see here, this species it called a Beipiaosaurus,

So, because this is a very not like us, two or three meters long,

so quite a big animal. And here is an arm,

hand, you see here...

dark filamentous structures... -yes.

along that arms and hand, they are actually primitive feathers.

And those feathers very simple, very simple,

so we believed they represent the very primitive stage for feather evolution.

These simple strands were made of the same material

as the feathers of today Birds.

They were relatively thick and must have been quite stiff,

so they would of stuck out beyond the dinosaur arm.

Behind them, were shorter strands that covered its all body.

Like the down on the chick, these might have kept the dinosaur warm.

But those long strands most likely had a different function.

Clues to what that might have been can be found

on an even more extraordinary fossil.

These claws and finger bones belong to a creature called Caudipteryx.

The long dark shapes around them are the remains of feathers.

The single strands are here rather more complex.

They had barbs, thin filaments attached to either side of a central rod.

This look more like a bird feather.

Caudipteryx had around 26 of them along each arm.

This may look like a wing, but the feathers were not very long.

And when you compare them to the size of this creature body,

and its long legs, it's clear

that they weren't big enough to enable Caudipteryx to fly.

So, what were these feathers for?

Microscopic examination has revealed that they were colored and patent.

So, maybe they were used for display,

perhaps to wave around during courtship to attract a mate.

But then is seems that they also helped the dinosaur in a different way.

We can find a hint of how they might have done this,

by watching the way some young birds use their first feathers today.

These are tender old Pheasant chicks.

Their feathers are not yet fully developed.

At this stage they similar in structure to the feathers on that dinosaur, Caudipteryx,

and going aline along each arm in much the same way.

But these early feathers are also too short to enable these creatures to fly.

Nevertheless they very helpful.

Pheasant chicks has to nest on the ground,

but they soon need to roost high up, where they are be safe from predators.

Flapping these simple wings gives the chicks a little extra lift

to help them climb into a tree.

And when the time comes to return to the ground,

those first feathers again are a help.

They don't provide a large air-catching surface,

but they enough to slow a chick fall,

and make that landing just a little softer.

Maybe the feathers that had initially kept the Dinosaurs warm,

now also help them to get into the air.

And then, only a few years ago,

the mudstone of Liaoning produce yet another extraordinary fossil.

It been named Microraptor, and it clearly a small dinosaur.

But this specimen it particularly exciting, because of its feathers.

Feathers on the forearm there.

Feathers on its hind limbs.

And even feathers right at the end of its very long tail.

But there is something that makes these feathers

different from any other feathers you seen on Dinosaurs before.

They are narrower on one side of the quill than on the other.

Just like bird feathers.

Microscopic structures within them suggest that they had flashes of iridescence.

So, these feathers were probably use 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 had 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 shape feathers certainly suggest

that its arms were been used as wings.

This four wing dinosaur must had 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 joined the Pterosaurs in the sky.

And then, around 130 million years ago the True Birds appeared.

And here, on the Lochs in Scotland are some of the most majestic

of those little around today.

Whooper Swans.

These particular birds were in contact with human beings

from the very first moment of their 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 and the barbs,

zip together to form a continues surface which will strong enough to hold the air.

But if the air is to support a wing 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 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 propelled them forward and lift them upwards.

So, how the bird wings actually work?

If we slow them down we can watch in detail the mini 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 of the front, and a sharp trailing edge of the back

they have a classic aerodynamic shape that produced lift.

They are aerofoils.

With this 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 changed its shape

there is no loss of smoothness on the contour.

When the Swan slightly retract its wings in between beats,

the sliding feathers ensure that the aerofoils still produces lift.

And the bird bodies have become modified in another way.

They become light weight.

The Dinosaurs heavy bony jaws lined with teeth

have been reduced to a light weight beak of horn.

The bony tail has shrunk to a stump, nearly an attachment point for the tail feathers.

And many of the bones within the body had become hollow,

so reducing weight even further.

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 appeared on the bodies of Dinosaurs,

have acquired several different functions.

Initially they served to keep their owners warm.

Then, some grew large and acquired color and were probably use in courtship displays.

And only then, after millions of years,

where they used to help their owners get into the air.

But the Birds were not the last animals to acquire the ability to fly.

When the Pterosaurs vanished together with the Dinosaurs,

there was room in the skies for yet another aeronaut,

And one appeared with yet another kind of wing.

Animals on our Planet have flown for over 320 million years.

First came insects, then a group of winged reptiles, Pterosaurs,

and next, Birds.

Then, around 66 million years ago, came the global catastrophe

that triggered the disappearance of a vast proportions 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 dominants creatures of that age,

the Dinosaurs, disappeared.

The Pterosaurs were completely wipeout.

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 had a chance for a group of furry warm blooded little creatures,

that has been scampering around the feet of the Dinosaurs for several millions years.

They were the mammals.

The first of them to take to the air were doubtous gliders.

And one mysterious creature still alive today,

can give us an idea of what there were like.

It lives in the rainforests of Borneo, and it called the Cobego.

It has an enormous blanket of furry skin that stretched

from the sides of its head right down to the very tip of its tail.

But to see how he travel through the air, we must wait until nightfall.

As soon as it lands, it regain the height it inevitably lost

by clambering up the trunk.

It by far the most skillful of the forest gliders,

and can travel over a 100 meters in one leap.

It undoubtedly a very ancient animal, and some believe that it may well

have survived virtually unchanged from that time long ago

when mammals first took to the skies as gliders.

But soon, the mammals deed better than that.

This is a fossil that dates from about 52.5 million years ago.

Here its head, a very well develop teeth, backbone and ribs,

a long tail, hind legs, and most importantly of all,

from our point of view, hands with enormously elongated fingers.

And there was skin between those fingers.

These were wings and they could flap.

This is the earliest fossil yet discovered of a bat.

We have new evidence to show exactly how a bat fingers

first began to lengthen to support their wings.

But we can understand how those early bats flew,

by looking on their modern descendants.

These are some of the largest.

They so big, that they often called Flying Foxes.

And they have a wingspan of over a meter.

When you slow a bat flight down like this,

you can see that its four fingers are spread wide under down stroke,

keeping the membrane wide and taut, and then clump together on the up stroke,

with just a thumb off the top three.

This folding of the wings reduces the bat air resistance between each beat.

To maximise the size of its wing, the back edge of the wing membrane

is attached to the ankles.

Bats roost by hanging upside down.

And this is how they tend to spend their days.

Is thought that the first mammals were nocturnal,

that doubtless was the best thing to be out of the way of the Dinosaurs

that were rampaging around during the day.

So, the bats continue the nocturnal habit of their ancestors,

and they are also inherited the acute sensors needed to move around at night.

Eyes specially adapted to operating well in low light.

And an acute sense of smell that enable them to find food in the dark.

In any case, Birds already dominate in the daytime skies.

With their wings of skin and nocturnal senses

the Bats became a hugh global success.

Today there are over 1,100 species of them,

that's over a fifth of all mammals.

So, by 50 million years ago, three groups of large backbone animals

had joined the Insects in the air.

The pioneers were reptiles, Pterosaurs,

with membrane of skin stretch from elongated fingers.

Then, came a group of Dinosaurs that acquired feathers and became Birds.

But when the Pterosaurs and Dinosaurs were swept away in a global extinction event,

the stage was set for the Birds and the newly emerge Bats

between them to take command on the skies.

Each of these two groups had evolved its on techniques for getting into the air,

and each was destined to bring theirs skills to astonishing extremes.

Next time, we see how Birds adapted and diversified

to become the remarkable creatures we see in our skies today.

Lethal hunters...

formation flyers...

an aerial acrobats.

We explore how the Bats develop a new super sense

that enable them to hunt in the pitch-blackness of the night.

And we visit one spectacular place were the battle for the skies,

between Insects, Bats and Birds still continues.

English: Bobiko

Written and Presented by David Attenborough