All language subtitles for david.attenboroughs.conquest.of.the.skies.s01e03.bdrip.x264-haggis

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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 skills
enabled them to surpass
Earth's original flyers, 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.

And 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 particularly 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
specialized 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 behavior 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.

And the vultures know exactly
how to exploit those thermals

to be carried high in the sky
with a 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 2 meters.

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

travel a shorter distance
than its outer wing.

And 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 a thermal and soar upwards.

Using this technique, a vulture can
climb to a height of a kilometer

above the ground,
with scarcely of flap of its wings.

And 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 wingbone 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 wingbone
of a vulture, and as you can see,
it has been broken, and it has healed.

It's owner may well have lived
to soar again.

This soaring tehnique
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 wingtips,
enabled larger birds to stay airborne.

But other birds faced
very different challenges
and so evolved different specialities.

To watch a bird that has evolved into
one of the worlds 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.

And 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 it's to get a meal.

A Peregrine 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 flyers,

and their smaller size
makes them even more maneuverable.

So, to catch a starling,
a Peregrine must be even faster,

and 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 toward 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 200 miles an hour.

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 the Peregrines.

One that relies on their ability to fly
together in tight formations, as a flock.

And here they come, vast numbers of them,
tens of thousands, hundreds of thousands.

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

And now, some start to fly
closer together, and perform
far more complex maneuvers.

Look how these great flocks,
come together, form a cloud,
veer away, and 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 defense,

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 analyzing
the flight paths of these Roman flocks,

have now revealed
how they manage to do this.

Just how they achieved 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 that
you look at them you wonder,

how it is possible that so many birds
could 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 flocks
complex manouvers in three dimensions.

Advanced computer software
then locks onto the flightpaths
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 allow 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 Peregrin's
diving attack, proves too strong.

Out of the millions of Starlings
in the skies,

only a few will fall prey
to the Peregrins tonight.

As the light finally fades, the flock
suddenly descends into the trees,

that will be their roost for the night.

The Peregrine's 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.

And 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 behavior,
they can hover.

And 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 surface.

Twisting this wing
at the shoulder and at the wrist,

produces the hummingbird's
distinctive wing-beat.

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 a 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 wing-beat,

not the flapping itself,
but the twists 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 flyers, 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:

The Barn Owl.

And one of its favorite meals,
is a field mouse.

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 disks 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 wing beats 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 field mouse 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're able to navigate
in total darkness.

Among insects there are some moths,
whose elaborate antennae

are able to pick-up
the scent 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 cabins.

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 are I'm interested in,
are further behind me in the semi-darkness,

and they're sleep 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 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.

And if you see 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 crowds,
hanging form 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 echolocation, 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 bats' echolocation 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 nightskies,
the bats don't have it all their own way.

A team of scientists in Borneo is studying
the way bats interact with their prey.

First, they catch a bat in a trap

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

There he is.
- Nice.

Beautiful
- Yeah he's gorgeous.

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

and so what we 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.

Everything set up here?
- Yes, 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 many moths
have bat detecting ears,

they can hear the bats coming,
they hear their echolocation 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 echolocation cries
with their own sounds.

All ... is now in 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 pulse 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 bats 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 defenses.

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 echolocation 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
that echolocation.
There they go!

But this is just a trickle,
the main exodus

is taking place up a chimney
that's 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 crowd,

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'd shared 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 echolocation to find food.

The way that 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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