All language subtitles for David.Attenboroughs.Conquest.Of.The.Skies.S01E03.Triumph.2160p.NOW.WEB-DL.DDP5.1.H.265-RAWR_track3_[eng]

I'm several hundred feet
up in the air.

Up here, I might encounter
perhaps a flying insect,

though I haven't seen one yet,
or maybe even a baby spider

clinging to a gossamer thread
of silk,

which is their way of getting
around.

But by and large,
this is the kingdom of the birds.

The first birds
flew about 150 million years ago.

They spread around the globe

and evolved into a multitude
of different kinds.

Aerial acrobats.

Stealthy hunters.

And some of the fastest
creatures on the planet.

Their extraordinary skill
enabled them

to surpass Earth's original fliers -
the insects.

But there is a vast kingdom
that the birds do not control -

the night skies.

These are ruled by very different
creatures -

flying mammals, bats.

And in one spectacular place

these two populations of the night
and the day collide.

This is Segovia in central Spain.

Some of the inhabitants of this
gorge allow us to see very clearly

how birds as a group have become
so versatile in the air.

Through the ability to
change the shape and the size

of their basic flying mechanism,
the wing.

There's a wonderful
example of that just over here.

You may think that birds are much
the same when it comes to flight,

but in fact different species need
to fly in their own particular way.

This vulture is an airborne
scavenger.

It feeds on the bodies
of dead animals,

so it needs to spot any fresh
carcass very quickly

and get to it
before others claim it.

Like most birds,
it has superb eyesight.

So it climbs high in the sky,

constantly scanning
the ground below,

for hours at a time if need be.

To fly in this highly
specialised way,

it has evolved a very
distinctive kind of wing.

To get up close to some of the many
vultures that live in this area,

I'm visiting a place where they're
regularly fed by conservationists.

These are griffon vultures,

one of the largest of all
vulture species.

Each one can weigh up to 11 kilos.

Lifting an 11 kilo body
high into the sky

takes a lot of energy,

but the vultures don't supply that
energy directly themselves.

A clue of how they do so comes from
observing their behaviour

at the start of the day.

Those vultures roost
and nest on ledges up there.

They're not early risers.

That's because they rely on the sun
to get airborne.

As the day warms up,
patches of bare rock

reflect the heat of the sun

forming columns of rising hot air
known as thermals.

The vultures know exactly how
to exploit those thermals,

to be carried high in the sky with
the minimum of effort.

They have wings that have been
shaped over millions of years

to catch as much of that rising
air as possible.

They're huge - very broad with
a span of over two metres.

But riding thermals may not be
as easy as it looks.

A thermal is quite a narrow
column of rising air

and to stay within it, a vulture
has to make quite sharp turns,

and that can lead to disaster.

In a tight spiral,
a vulture's inside wing

travels a shorter
distance than its outer wing.

If we were to measure
the speed of this inner wing,

we would find that it moves much
more slowly through the air.

This means it generates less lift.

So little, in fact, that the
vulture could easily stall

and drop from the sky.

It avoids that by having
special control

over the feathers at the ends
of its wings.

They can be splayed
so that they separate.

As a result, each feather
acts as a small extra wing,

and together
they increase overall lift.

This enables the vulture to
turn in a tight circle

and so hold its place in the thermal
and soar upwards.

Using this technique a vulture can
climb to a height of a kilometre

above the ground with scarcely
a flap of its wings.

Then, if it spots food down below,

it can switch its flying technique
and descend at speed.

Once on the ground, it has
to compete with other vultures

for a share of the feast.

And now,
those broad wings are useful,

to help muscle out its rivals.

And that can put those all
important wings at risk.

Bird bones,
being hollow and lightweight,

are also usually very fragile.

And if a bird breaks its wings,
that's usually a death sentence,

because most small birds
have to feed every day or so.

But this is the wing bone
of a vulture.

And vultures are so big and can fill
their stomach with so much food,

that they can go without a meal
for two or even three weeks.

And as a consequence, when these
aggressive, quarrelsome vultures

have a row
and perhaps injure one another,

a broken wing can heal itself.

And this is the wing bone
of a vulture.

As you can see, it has been broken,
and it has healed.

Its owner may well have lived
to soar again.

This soaring technique can exploit
not just the thermals,

but also winds deflected
upwards by ridges and hills.

The same wing shape is used by other
large birds to help them soar.

Eagles.

Pelicans.

And a bird that makes an immense
journey here to Spain every summer.

Two young storks.

Their parents come here every year
to this small town in northern Spain

in order to mate and nest
and rear their young,

all the way from Africa.

Some from as far south as the Cape.

And they make that immense journey

by finding a thermal,
a column of rising air,

circling in it, allowing it
to carry them high into the sky,

and then gliding off
on the next stage of the journey

to find another thermal
to take them back up again.

It's an extraordinarily
energy-efficient way of travelling.

So broad wings and splayed wing tips

enabled larger birds
to stay airborne.

But other birds faced
very different challenges,

and so evolved
different specialities.

BELLS TOLL

To watch a bird that has evolved

into one of the world's
most skilful hunters,

I've come to Italy
and the city of Rome.

There's a bird that flies over
these roofs

that finds its prey
not on the ground but in the air.

It owes its success to its speed.

In fact, it's said to be the fastest
moving animal on Earth -

the peregrine.

Peregrines hunt other birds.

Many different kinds of birds
now live in cities,

attracted by the food and shelter
that is so easily found here.

And a tall building like this is
an ideal lookout for a hunter.

Flying prey can move in
any direction it chooses,

so a hunter has to be both fast
and agile

if its to get a meal.

A peregrine's wings have
a very special shape.

They're pointed and swept back.

If wings have a blunt end,

air will swirl over that end,
forming trails of turbulence.

These act like brakes,
slowing a bird down.

But pointed wings shrink that edge
and so reduce the turbulence.

Pulling the wings back towards
the body

makes the bird even more
streamlined.

And speed is crucial
to a peregrine's success.

It also has acute vision

that enables it to spot prey
over a mile away.

And for the peregrines
that hunt in Rome...

...these birds are
prime targets...

starlings.

They too are fast fliers.

And their smaller size makes them
even more manoeuvrable.

So to catch a starling,
a peregrine must be even faster.

In order to gain speed and surprise,

it attacks from above.

First, it climbs.

When it sees a group
of its potential prey,

it turns...

dives...

and accelerates
by beating its wings.

The starlings are still unaware
of the danger hurtling towards them.

Finally, the peregrine draws
its wings back.

This is called the stoop,

a superb streamlined shape

that slices through the air.

Now it can reach
speeds of over 200mph.

As it nears its target,

it opens its wings
to slow its descent

and makes its final lunge.

Starlings, in fact, are an abundant
source of food

for the peregrines.

They come into the city
in the winter,

attracted no doubt by the warmth
in order to roost.

Every evening at dusk,
the starlings start to arrive,

and they have a remarkable way
of defending themselves

against peregrines.

One that relies on their ability
to fly together

in tight formations as a flock.

Here they come -
vast numbers of them.

Tens of thousands,
hundreds of thousands.

It's like a great black hail storm,
a blizzard of birds.

And now some start to fly
closer together

and perform complex manoeuvres.

Look how these great flocks
come together,

form a cloud, veer away, then split.

It's a quite extraordinary piece
of aerial navigation.

We're still unsure exactly why
they perform these elaborate dances,

but they're often triggered
by the arrival of a predator.

And today is no exception.

Because over there
on one of those buildings,

I've seen a peregrine.

Coming in in great numbers like this
is in itself a defence,

because if you're surrounded
by tens of thousands of others,

well, it's a good chance
that the peregrine won't get you.

But the aerial ballet is part of a
more complex defensive strategy.

When a peregrine does attack with
its wings drawn back in its stoop,

the starlings, flying in their tight
formation,

coordinate their escape.

Instead of scattering in different
directions,

when a straggler might be
picked off,

they stick together, even when
they make the sharpest of turns.

Recent studies analysing the
flight paths of these Roman flocks

have now revealed how
they manage to do this.

Just how they achieve this was not
understood until very recently.

But now, a team of physicists
from Sapienza University in Rome

is beginning to find the answers.

We see these huge flocks of birds
dancing in front of us.

And every time you look at them,
you wonder how it is possible

that so many birds would be
as only one entity.

They position a series
of cameras along a rooftop

overlooking
a favourite starling roost site,

just outside Rome's main
railway station.

The cameras record
the flock's complex manoeuvres

in three dimensions.

Bellissimo.

Advanced computer software

then locks on to the flight paths
of thousands of individuals

with extraordinary precision.

Their painstaking work has produced
a remarkable insight

into how the starlings
coordinate their behaviour.

The main result that we found

is that each bird interacts
with the seven birds around it,

regardless of the distance
between these birds.

It is the key to have a stable flock.

An individual starling

is effectively linked
to the seven around it

by an invisible web, even if
they drift far apart.

This is the hidden glue
binding the flock together.

But it may also act
as a communication channel.

A bird that turns to evade
a predator triggers a ripple effect,

that passes rapidly
through the overlapping networks,

causing the whole flock
to turn as one.

The special thing
is that the information

can pass through the flock
in milliseconds,

and this allows them to escape
very quickly from predators.

Most of the time, the starlings'
flock defence keeps them alive.

But now and again,
the sheer speed and surprise

of the peregrines' diving
attack proves too strong.

Out of the millions
of starlings in the sky,

only a few will fall prey
to the peregrines tonight.

As the light finally fades,

the flock suddenly descends
into the trees

that will be their roost
for the night.

The peregrines sharp eyesight
doesn't operate

nearly so well in the dark.

So now the starlings are safe...

until tomorrow, that is.

6,000 miles away in South America,

there are other birds
with a very different skill.

They also find their food
on the wing.

In the cloud forests of Ecuador
there is a plentiful supply

of a type of food produced by plants

to attract flying animals...

nectar.

Around 130 million years ago,

plants recruited insects
to transport pollen,

from one flower to another,

by bribing them
with a sugar-rich drink.

Birds, when they first evolved,
were unable to collect it

because there was seldom
something solid nearby

on which they could perch.

Then, around 30 million years ago,

a kind of bird appeared
that had no need of such a perch.

Hummingbirds.

They could hover.

They do so by beating their wings
extremely swiftly.

So fast, in fact, that they
make a humming noise.

The largest hummingbird beats
its wings around 14 times a second,

but some tiny species are able
to do so 80 times a second.

To fly in this extraordinary way,

hummingbirds have changed
the structure of their wings

and the way they beat them.

Here in Ecuador,

scientist Doug Altshuler
is working to analyse

exactly how they do so.

Hummingbirds are remarkable animals.

They have extreme adaptations
in physiology and anatomy

and they also have a very unique
behaviour - they can hover.

The approach
that we've taken is to study

how those physiological
and anatomical adaptations

determine their hovering ability.

Using high-speed cameras,

he records the mechanics
of their flight in minute detail.

He can slow down the action
by around 40 times

and so observe exactly
what's taking place.

Most birds flap their wings
up and down.

But hummingbirds flap theirs
more like insects.

They twist their wings around
between strokes

and so can generate lift

when flapping both forwards
and backwards.

Doing this at high speed
puts a huge strain on their wings.

So to withstand it,
the wings have a special structure.

The hummingbird wing is very stiff

and undergoes few changes in shape
as it rapidly beats back and forth.

They owe this stiffness
to a modification of the bones.

The arm bones have shrunk,

but the bones of the hand
have elongated

and support most
of the wing's surface.

Twisting this wing at the shoulder
and at the wrist

produces the hummingbird's
distinctive wingbeat.

Doug is also investigating

one of the great mysteries
of hummingbird flight -

their ability to move sideways
in mid-hover.

Hummingbirds are able
to track flowers

that are moving back and forth
in the wind

and this was something I always
wanted to know more about.

To replicate the swaying motion
of the flower,

Doug places a reservoir of nectar
on a mechanical slider.

Before long, he has a volunteer.

Amazingly, it manages
to track sideways

to keep up with the slider
and still feed.

The bird is exploiting an unexpected
feature of its wingbeat -

not the flapping itself,

but the twist at the end
of each stroke.

During hovering flight,
as the wings come forward,

they rotate symmetrically,
so the forces remain in balance.

But if they instead
rotate differently,

such that one wing rotates
before the other,

then the forces are no longer
in balance

and this asymmetry can be sufficient

to push them to one side
or the other.

So a combination
of modified wing bones

and precise control of wing motion

gives hummingbirds
the aerial agility they need

to collect nectar.

And they need plenty of it -

hovering burns a huge amount
of fuel.

All hummingbirds have to
constantly top up their tanks

with high-energy nectar.

And when supplies are low,
competition can be fierce.

Now, their flying skills are put
to a very different use -

to fight off rivals.

So different birds
adapted their wings

to fly in highly specialised ways.

Some began to hunt the earth's
first fliers - the insects.

And in that battle,
there is now no real contest.

But because most birds rely
for so much of their success

on their exceptional eyesight,

there is one major habitat
that is largely closed to them.

Not a place, but a time.

The night.

In the British countryside, however,

there is a bird
that can fly in the dark.

A barn owl.

And one of its favourite meals
is a fieldmouse.

But first, it has to find it
in the dark.

A mouse is extremely alert
to the approach of a predator.

But the barn owl has wings
specially adapted for stealth...

...and senses that can
penetrate darkness.

Its eyes are very sensitive
in low light,

but even if the mouse
is out of sight,

it's still not safe.

The owl's hearing
is also very acute.

Those two discs on its face
channel sound into its two ears,

which are on a slightly
different level on the head.

And that difference enables the bird
to pinpoint the source of the sound,

whether it's in the air,
or down on the ground.

But in order to hear that sound,

its wingbeats have to be
very, very quiet.

And the way it achieves that
we can see when it goes hunting.

The key reason for its silent flight

lies in the nature
of its wing feathers.

Along the back edge,
their fringe is frayed and tatty.

Most birds' wings have a hard edge

and this can cause
quite a loud noise.

The source is turbulence,

produced when air flowing over
the wing rubs against its surface.

When this swirling air
meets a hard back edge,

the sudden drop-off
hugely amplifies the noise.

But the barn owl's tatty feathers
avoid that -

by creating a softer edge,
they cushion the turbulent air

and so reduce noise.

So silent flight allows the owl
to hear its prey

and conceals its approach.

But to position itself for the kill,
it needs to fly extremely slowly.

And to achieve that,
it has particularly broad wings.

This slow, silent approach

leaves a fieldmouse
little chance of escape.

On nights when there is thick cloud
or no moon,

even an owl's sensitive eyes
struggle.

But there are creatures that have
such highly specialised senses

that they are able to navigate
in total darkness.

Among insects, there are some moths

whose elaborate antennae
are able to pick up

the sense of food, or a mate.

And there are
those nocturnal animals,

the last group of flying creatures
to appear on Earth - the bats.

To see how they battle
with the insects

for dominance of the night skies,

we're heading into the rainforests
of Borneo.

Many bats find their food
not by sight or smell,

but by using a very different
and highly advanced guidance system.

One way to find them
is to search for their ideal home -

a place like that deep,
black cave beneath me.

If you fly at night,

there's no better place
to spend the day

than in a cave like that.

This is Gomantong.

The cave is a vast network
of underground tunnels

and cathedral-sized caverns.

It was carved out by streams
of water over millions of years.

And now,
it's home to a remarkable community

of cave-dwelling specialists.

To find the creatures
I'm looking for,

I'm being winched high up
towards the ceiling,

where the towering walls make ideal
roost sites for flying animals.

These little birds flying past me
are swiftlets

that have made their nests
on the walls of the cave.

They are active during the day

and they leave the cave
to hunt insects.

The bats that I'm interested in
are farther behind me,

in the semi-darkness,

and they're asleep now,
during the day.

The bats are scarcely
the size of mice.

Their wings are constructed
with very long fingers

and they hang by their feet
from the rock.

Although there are a few
at the back there,

deeper in this cave,
they exist in huge numbers.

To find their roosts, we're heading
still deeper into Gomantong Cave.

High on the rocky cave ceiling
above me, hidden in the darkness,

there are vast numbers of bats.

You can get some idea
of how many there must be

because of this huge dune behind me.

That's formed of their droppings.

If you see a little moving
glints on the surface,

that comes from an army
of cockroaches

which are chewing their way through
the bat droppings

to extract
the last particles of nutriment.

Some people think there are
a million bats up here in this cave.

It's impossible to see them
in the gloom.

But special night vision
cameras can reveal them,

densely packed,
hanging from the ceiling.

Their tiny eyes are adapted to
low light,

but they cannot
penetrate the blackness.

Millions of years ago, however,
these bats evolved

an extraordinary guidance system
known as echo location, or sonar.

A bat produces extremely
high-pitched sounds in its throat

and then projects them forward.

We have slowed the sounds down,
but can still only hear them

by converting them
to lower frequencies.

They bounce off the walls as echoes

and are detected
by the bat's huge ears.

These are in constant movement
and enable the bat

to map its surroundings
with remarkable precision.

But these bats not only need
to find their way in the dark,

they also need to find their food...

...night-flying insects.

And among them are moths.

Locking on to these moving targets

is a supreme test for the bat's
echo location system.

As one homes in, its sonar beam
switches into attack mode,

increasing the rate of its pulses.

This enables it to precisely
pinpoint the location of its prey.

But in the battle
for the night skies,

the bats don't have it all
their own way.

A team of scientists in Borneo

is studying they way bats interact
with their prey.

First, they capture bats in a trap

that uses thin wires to divert them
into a pouch below.

There he is.
Nice.

Beautiful.
Yeah, he's gorgeous.

I'm shining through. Yeah.
Ah, cool.

Bats and moths have co-evolved
for almost 60 million years.

And so what we're doing here

with this giant tent
and all these cameras

is to try and figure out what's
happening in this ancient battle.

Trying to understand how moths
survive a bat attack.

Set up here?
Yeah, everything's ready to go.

Awesome.

The tent acts
as a controlled flight arena

in which every movement and sound
can be recorded in minute detail.

Filming these interactions
with multiple cameras in 3D,

and ultrasonic microphones,

we can see
how these interactions unfold

and to hear how they unfold.

These studies have revealed

that moths don't always fall prey
to the bat attacks.

We know that mini moths have
bat-detecting ears,

they can hear the bats coming.

They hear their echo-location cries,

and dive out of the sky,
stop flying.

Got it? There you go.

But the team's work
has identified a moth

with a very different
defence strategy.

Playing recordings
of bat sounds to this moth

reveals a remarkable ability.

Here in Borneo, we recently
discovered that hawk moths

respond to these echo-location
cries with their own sounds.

Oh, lots of sound production.

Hawk moths do it with
the tip of their abdomen,

with modified genitals.

They rub the genitals
against the inside of the abdomen

and reply to this bat attack.

The moth is tethered

to keep it in range of the cameras
and microphones.

Then a bat is released.

As the bat approaches the moth,

its sonar pulses switches
to attack mode.

But now the hawk moth responds,

sending its own rasping sound back
with astonishing effect.

At the last moment, the bat appears
to lose track of the moth

and fails to catch it.

We've shown that these moth sounds
actually jam the bat's sonar.

They interfere with the returning
echoes from the insect

and causes the bat to miss the moth.

The team has discovered that
insects are fighting back

in the ongoing battle
for the night skies.

But there are, of course,

plenty of other flying insects
with no such defences.

And they live in vast numbers in the
forests outside Gomantong cave.

So every evening, as dusk arrives,

the bats leave the safety
of their secluded home to hunt.

And now the bats are beginning
to use their echo location skill

to fly out from their roosts
in the depths of the cave,

coming close to the ceiling

and then whizzing out through
this little entrance here.

They don't collide with the roof,

they don't collide with one another,
or even with me,

all through echo location.
There they go.

But this is just a trickle.

The main exodus is taking place up
a chimney that deeper in the cave.

To watch, close up,

the way the bats achieve
their million strong mass departure,

I'm being hauled up 200 feet
into the funnel

which serves as one
of the cave's main exits.

At the top, there is a gaping hole.

And now the bats are preparing
to leave.

They've assembled in a relatively
small chamber close to the exit

and are flying round and round
in a great swirling cloud,

waiting for daylight to fade.

And now off they go!

This brief hour of dusk is the
moment when the two communities -

the day flyers
and the night flyers -

may encounter one another
in the air.

Outside, danger awaits.

Hunters belonging to that other
great group of animals

with which they share the skies -
birds.

Hawks, eagles and kites.

They are why the bats were
reluctant to leave.

And why they now do so
in one continuous torrent.

There is safety in numbers.

But some will pay the price.

The vast majority, of course,
make it out over the forest canopy

and there they can use that
skill of echo location to find food.

The way the different animals have
colonised the skies is surely

one of the most remarkable
stories in the natural world.

First to do so, over 320 million
years ago, were the insects.

They had no competition
for about 100 million years.

But then, much larger flying animals
took to the air -

reptiles, the pterosaurs.

Around 70 million years later still,

one branch of the dinosaurs
acquired feathers

and that enabled
their owners to get airborne.

The birds had arrived.

And lastly,
about 60 million years ago,

the night skies were
invaded by mammals - the bats.

And here, in Gomantong cave, the
three surviving groups of flyers -

insects, birds and bats -

are still locked together
in an ongoing evolutionary struggle.

So the battle for the supremacy
of the skies

that started
over 300 million years ago

still continues every day
around the world.

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