Original subtitles

English: Bobiko

I'm several hundreds feet up in the air,

up here, I might encounter perhaps a flying insect,

although I haven't seen one yet,

or maybe even a baby spider clinging to a gossamer of thready silk,

which is their way of getting around.

But by in 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 enable them to surpass Earth 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.

~ Conquest Of The Skies ~

- TRIUMPH -

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, their wing.

And there is 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 need to spot any fresh carcass very quickly,

and get to it before others claim it.

Like most birds, it has superb eyesight.

So, it climb high in the sky,

constantly scanning the ground below,

for hours at a time if need be.

To fly in this highly specialize way,

it is evolved a very distinctive kind of wing.

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

I visiting a place where they regularly fed by conservationists.

These are Griffon Vultures, one of the largest of all birds species,

each one can weight up to 11 kilos.

Lifting a 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 not early rises.

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

As tha 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 carry high in the sky with a minimum of effort.

They have wings that have been shaped over millions of years

to catch as mush of that rising air as possible.

They huge, very broad, with a span of over 2 meters.

The 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 could lead to disaster.

In a tight spiral, a vulture inside wing

travel a shorter distance than its outer wing.

And if we were to measure the speed of this inner wing,

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

This mean it generates less lift.

So little in fact, that the vulture could easily

stall and drop from the sky.

It avoid 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 enable 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 climbe to a height of a kilometer

above the ground with scarcely of flap of its wings.

And then, if it spot food down below,

it can switch its flight technique and descend at speed.

A dead animal, once found, makes an easy meal,

except for the fact that there are rather a lot of dinners.

But other meat eating birds have even greater problems.

They pursue living prey, and one such hunter

has become one of the fastest of all living creatures.

To watch one of the fastest of all flying animals,

I have comed to Italy and the city of Rome.

There is a bird that fly over these roofs,

that find its prey not on the ground, but in the air.

And it owe its success to its speed.

In fact, it 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 to get a meal.

A peregrine wings have a very special shape.

They pointed and swept back.

If wings have a blunt end, air will swirl over that end,

forming trails of turbulents.

These act like brakes slowing a bird down.

But pointed wings had shrink that edge, and so reduce the turbulents.

Pulling the wings back towards the body, makes the bird even more streamlined.

And speed is crucial to a peregrine success.

It also has acute vision that enable it to spot prey over a mile away.

And for the peregrine that hunt in Rome, these birds are prime targets.

Starlings.

They too are fast flyers,

and their smaller size make 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 accelerate 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 streamline shape that slices through the air.

Now, it can reach speed of over 200 miles an hour.

As it neared its target, it open its wings

to slow its descent and makes its final launch.

Starlings in fact, are an abundance 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.

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 closely 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 still unsure exactly why they perform these elaborate dances,

but they often triggered by the arrival of a predator.

And today is no exception, because over there,

on one of those buildings I have seeing a peregrine.

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

because if you 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 drawing back in its stoop,

the starlings flying in their tight formation coordinate their escape.

Instead of scattering in different directions when a struggler might be picked off,

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

Recent studies analyzing the flight birds of these Roman flocks,

have now revealed how they manage to do this.

Each individual starling is constantly tracking the movements

of up to 7 of its close neighbors,

even if they drift far apart.

This is the hidden glue binding the flock together.

And it can also help the birds to communicate among themselves.

A bird that turns to evade a predator triggers a ripple

that passes through the overlapping networks in milliseconds.

And that causes the all flock to turn as one.

As the light finally fades, the flock suddenly descend 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.

And they also find their food on the wind.

In the Cloud Forest of Ecuador there is a plentiful supply of a type of food

produce 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 where 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 beat 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 have taken is to study how those

physiological and anatomical adaptations determine their hovering ability.

Using High-Speed cameras, he record the mechanics of their flight in minute detail.

He can slowdown 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 put a huge straying on their wings.

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

The hummingbird wing is very stiff, and undergo a 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 of the shoulder and at the wrist

produces the hummingbird 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.

Befor 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 froces remain in balance,

but if they instead rotate differently, so that one wing rotate before the other,

then the forces are no longer in balance,

and this asymmetry can be sufficient to push them to one side of 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 at their tacks

with high energy nectar.

And when supply 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 specialise ways.

Some began to hunt the Earth 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 close 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.

And it's a very skillful hunter.

The Barn Owl is one of only a very few birds that can hunt at night,

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 different enable 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 to achieve that, we can see when it go hunting.

The key reason for it 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 turbulents produce when air flowing over the wing rub against its surface.

When this swirling air meet a hard back edge,

the sudden drop-off hugely emphasize the noise.

But the Barn Owl tatty feathers avoid that, by creating a softer edge,

they cushion the turbulent air and so reduce noise.

So, silent flight allow the owl to hear its prey,

and conceal its approach.

But to position itself for the kill it need 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 clouds or no moon,

even an owl sensitive eyes struggle.

But there are creatures that have such highly specialise senses

that they able to navigate in total darkness.

Among insects, there are some moths who their elaborate antenna

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 dominate of the night skies,

we heading into the rainforests of Borneo.

Many bats find their food not by sight or smell,

but by using a very different and highly advance guiding 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 is 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 cathedrals size cabins.

It was carve 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 been winch high up towards the ceiling,

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

These little birds try pass 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 interesting in, are further behind me in the semidarkness,

and there are 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 of the bats there,

deeper in this cave they exist in huge numbers.

To find their roosts we heading still deeper into Gomantong cave.

A huge black dune fill the back of one of the main chambers,

it made up entirely of the droppings of the vast numbers of bats

hanging above in the darkness.

To see them fly, we must wait for dusk.

The great tropical island of Borneo contains many huge caves,

and one of the biggest is Gomantong.

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 form of their droppings,

and if you see little moving glimpse on the surface,

that comes from an army of cockroachs which are chewing their way

through the bats droppings to extract the last particles of nutriment.

Some pepole 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 pack 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 evolve

an extraordinary guiding system known as echolocation or sonar.

A bat produces extremely hyper sounds in its throat,

and then project them forward.

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

by converting them to lower frequencies.

They bounce of the walls as echoes

and are detected by the bat huge ears.

These are in constant mevement 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 home in, its sonar beam switches into attack mode,

increasing the rate of its pulses.

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

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

A team of scientists in Borneo has discovered

that there is another creature here that uses sound as a weapon.

Everything set up here? -ye, everything ready to go. -awesome.

This tent act as an enclose flight arena,

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

With these cameras and ultrasonic microphones,

we can see how these interaction unfold,

and hear how they unfold.

The team play recordings of bats sounds to moths.

This reveals a remarkable ability.

Here in Borneo, we recently discover that Hawk Moths

respond to these echolocation cries with their own sounds.

Hawk Moth is now direction.

Hawk Moths do with the tip of their abdomen with modified genitals,

they rub the genitals against the inside of the abdomen,

and reply to this bat data.

The moth is tether 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 have shown that these moth sounds actually jam the bat 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 forest

outside Gomantong cave.

So, every evening as dusk arrive,

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

And now, the bats are been in use their echolocation skill

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

coming close to the ceiling and then wheezing 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 to 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 hold-up 200 feet into the tunnel

which serves as one of the cave main exits.

At the top, there is a gaping hole.

And now, the bats are preparing to leave.

They have assemble in a relatively small chamber close to the exit,

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

waiting dor day light to fade.

And now, off they go.

This refire 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 await,

hunters belonging to that other great group of animals

with which their shares 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 colonise 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 in the air.

Reptiles. The pterosaurs.

Around 70 million years later still,

one branch of the dinosaurs acquired feathers,

and that enable their owners to get airborne.

The birds had arrived.

And last in, about 60 million years ago,

the night skies where invaded by mammals, the bats.

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

insects, birds and bats,

are still lock 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.

Written and Presented by David Attenborough

English: Bobiko