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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