All language subtitles for David.Attenboroughs.Conquest.Of.The.Skies.S01E02.Rivals.2160p.NOW.WEB-DL.DDP5.1.H.265-RAWR_track3_[eng]

We human beings are very latecomers
to the sky,

and although we might think
that we're now pretty good at it,

the natural world, with the help of
several million years of evolution,

has produced a dazzling range
of aeronauts,

whose talents are far beyond ours.

The story of how animals managed
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
to 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 evolved several
ways of solving that problem.

We will travel the globe

to trace the details
of the extraordinary skills

of the backboned flyers.

Whoa!

This is Borneo.

And here, there are still great
tracts of pristine rainforest.

Forest that is wonderfully rich
in animals of all kinds.

I am being winched up into one
of the tallest trees here...

...in search of a creature
that could give us a hint

of how backboned animals
first took to the air.

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

is a very remarkable little frog.

It's a harlequin tree frog
and it's a very, very good climber.

It spends most of its life up here,
clambering 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 defence.

It glides.

It has membranes
between greatly elongated toes,

so that each foot becomes
a parachute,

which slows the frog's descent

and so enables it
to make a relatively safe landing.

The vertebrates made
their first forays into the air

around 260 million years ago.

And it's very likely that some of
these pioneers used skinny membranes

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

It has to be said that it's not
a very good aerial navigator.

It seems as though 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 lives.

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 dew lamp.

He also spreads coloured 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's side flaps now serve
another purpose.

He uses them to glide
by hitting forward

his specially elongated ribs.

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

and 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 it had the muscles needed

to beat its wings,
and computer imagery can show us

what it must have looked like.

Dimorphodon was one
of the first large animals

ever to travel by air,
200 million years ago.

It belonged to a group called the
pterosaurs - the winged reptiles.

It was probably a forest dweller

and a descendant
of a tree-living glider.

This gliding ancestor might have
had wings like those of draco's

that were made of skin

and perhaps extended
from its fingers down to its ankles.

But pterosaurs had evolved
larger wings

with a hugely elongated
fourth finger.

The wing membrane
was strengthened internally

by thin rods of a stiffer tissue.

There were muscle fibres, too,

that enabled it to modify
its contours as it flew.

Looking at the wings in section

reveals the secret
of their efficiency.

They have a rounded frontage
and a sharp back edge -

a shape known as an aerofoil.

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

This faster air has
a lower pressure.

And the wing is sucked upwards.

The larger the surface area
of the wing,

the greater lift it can produce.

So it seems certain that pterosaurs
were very competent flyers,

and, judging from their teeth,
it seems likely that many

fed on the great variety of insects
that had preceded them into the air.

Insects had had the skies
to themselves

for around 100 million years.

Now bigger creatures had arrived -
reptiles.

The pterosaur designed for flight
proved hugely successful.

They used their new powers
to spread beyond the forests

and colonise whole new environments.

A great number of them lived
and fed near water.

We know this because fossils
of many species occur in rocks

that were once mud at the bottom
of lakes and shallow seas.

This one shows
the skeleton of an animal

that 150 million years ago,

fell to the bottom
of a shallow lagoon.

This is its head.

Here's 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 shows
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 had these long jaws

with forward-pointing teeth.

And we think that indicates
that it lived

by skimming across the surface
of the lagoon and snatching up fish

it impaled on those teeth.

This very different one
is just the head.

As you can see,
it has very long jaws.

And at the tip of the lower one,

there's this little tuft
of very fine filaments.

And we know from other specimens

that those filaments
originally stretched

right along the length of the jaw.

This bristly fringe enabled
the creature to filter feed.

Taking in a beak full of water,

expelling it through the bristles
with the beak half closed,

and then swallowing
what the bristles retained.

And here is a skull of a very much
bigger species from Brazil.

And it had neither teeth nor
bristles in its jaws.

But microscopic examination
of the surface of the bone here...

...reveals very tiny
little blood vessels.

And that suggests that these jaws
were once covered with a horny beak.

So that maybe this animal used
its beak like a pair of forceps,

to pick up small little reptiles, or
maybe catch dragonflies in the air.

And this particular skull
reveals something else

about the lifestyle
of this specimen,

because at the back of the skull,
it has this great flange.

And pterosaur skeletons
from other species have been found,

some with such flanges,
but others without.

So it's thought that maybe this was
the difference between the sexes.

Maybe it was the male that had
these big flanges at the back,

which it displayed them,
and maybe it was covered with skin.

We can only guess.

Many different pterosaur species
evolved these head crests,

and it seems very likely
that they were covered.

This spectacular example
is known as tapejara,

and it made its home
beside inland lakes.

But pterosaurs diversified
in other ways, too.

Some evolved much larger bodies.

This species had a wingspan
of over twenty feet - seven metres.

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 has ever flown.

It was 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 toughened 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're still with us today.

They are, of course, the birds.

Some, today, can provide clues

about how their ancestors managed
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's to say, they're 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, to be precise.

To find evidence
for that astonishing statement,

which not so long ago
was highly controversial,

we're heading for China.

Northeast of China's Great Wall,

near the borders of Mongolia,

lies the chilly province
of Liaoning.

Here there are great areas of rocks
that were laid down as mud

in the bottom of immense
freshwater lakes.

The bodies of animals that were
swept down into these lakes

were slowly entombed
by the fine-grain 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've been delicately
prepared under the microscope.

They have been studied here

by one of the world's greatest
dinosaur experts -

Professor Xing Xu.

First, he showed me one of his older
specimens, part of a dinosaur's arm.

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

there's more here than just bones.

You see here,
this species is called a Beipiaosaur.

This animal is two
or three metres long,

so quite a big animal.

And here's the arm, hand.

You see here...

dark filament structures...

Yes.
...along the arms and hand...

actually primitive feathers.

And those feathers are very simple.

Very, very simple.

So we believe they represent

the very primitive stage
of feather evolution.

These simple strands are made
of the same material

as the feathers of today's birds.

They were relatively thick,
and must have been quite stiff,

so they would have stuck out
beyond the dinosaur's arm.

Behind them were shorter strands
that covered its whole body.

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

But those longer 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 looks
more like a bird's 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's 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 coloured,

and patterned, so maybe
they were used for display,

perhaps to wave around
during courtship to attract a mate.

But then, it seems, 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 ten-day-old
pheasant chicks.

Their feathers are not yet
fully developed.

At this stage, they're similar
in structure to the feathers

on that dinosaur, Caudipteryx,

and grow in a line along each arm
in much the same way.

But these early feathers
are also too short

to enable these creatures to fly.

Nevertheless, they're very helpful.

Pheasant chicks hatch in nests
on the ground,

but they soon need to roost high up,

where they'll 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're enough
to slow a chick's fall,

and make that landing
just a little softer.

Maybe the feathers that had
initially kept the dinosaurs warm

now also helped them
to get into the air.

And then, only a few years ago,

the mudstones of Liaoning produced
yet another extraordinary fossil.

It's been named Microraptor.

And it's clearly a small dinosaur.

But this specimen is
particularly exciting

because of its feathers.

Feathers on the forearms there,

feathers on its hind limbs.

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

But there's something that makes
these feathers different

from any other feathers
we've 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 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.

Oops!

But those aerodynamically shaped
feathers certainly suggest

that its arms were being 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 recognisable 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.

Those 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 tailfeathers.

This is the racket-tailed drongo.

And its tailfeathers
bear 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 continues 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 clear 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,

it seems she was not as impressed
as she might've 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
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's 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 what 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 upward.

Ooh.

So how do birds' 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 joined 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
lightweight flyer.

We're travelling around 30mph now,

and yet these birds could easily
accelerate and leave us behind

if they wanted to.

So feathers,

since their 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 was the chance for a group of
furry, warm-blooded little creatures

that had been scampering around
the feet of the dinosaurs

for several million years.
They were the mammals.

The first of them to take to the air
were, doubtless, gliders.

And one mysterious creature,
still alive today,

could give us an idea
of what they were like.

It lives in the rainforests
of Borneo.

And it's called the kubong.

It has an enormous blanket
of furry skin that stretches

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

But to see how it travels
through the air

we must wait until nightfall.

As soon as it lands, it regains
the height it's inevitably lost

by clambering up the trunk.

It's by far the most skilful
of the forest gliders,

and can travel over 100 metres
in one leap.

It's 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 did better than that.

This is a fossil that dates from

about 52½ million years ago.

There's its head,
the very well-developed teeth,

backbone and ribs,

long tail, hind legs,

and, most important 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 no evidence to show exactly
how bats' fingers first began

to lengthen to support their wings.

But we can understand
how those early bats flew

by looking
at their modern descendants.

These are some of the largest.

They're so big that they're
often called flying foxes.

And they have a wingspan
of over a metre.

When you slow a bat's flight down
like this, you can see

that its four fingers are spread
wide on the down stroke,

keeping the membrane wide
and taught, and then come together

on the upstroke, with
just the thumb at the top free.

Boy...

This folding of the wings

reduces the bat's 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.

It's 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 continued the nocturnal
habit of their ancestors.

And they had also inherited
the acute senses

needed to move around at night -

eyes, specially adapted
to operating well in low light,

and an acute sense of smell

that enables them to find food
in the dark.

In any case, birds already dominated
the daytime skies.

With their wings of skin
and nocturnal senses,

the bats became
a huge, 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 backboned animals

had joined the insects in the air.

The pioneers were reptiles -
pterosaurs -

with membranes of skin stretched
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 emerged bats,

between them,
to take command of the skies.

Each of these two groups had evolved
its own techniques

for getting to the air.

And each was destined to bring their
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...

...and aerial acrobats.

We explore how the bats developed
a new super-sense that enables them

to hunt in the pitch blackness
of the night.

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

between insects, bats and birds,
still continues.

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