Meat-Eaters The Life of Birds

*

Sparrows...

in South Africa. Like all sparrows, they eat most things -

insects, fruit and, particularly, seeds.

And they convert that diet into their own flesh, which is the richest of all foods - meat.

So they themselves are much hunted.

A falcon is also looking for a meal.

And it has one.

Meat is such a rich food that a falcon need only kill once a day to sustain itself.

So, plenty of time for sitting around. Nice work if you can get it.

But getting it is not necessarily all that easy.

This hillside in New Zealand may look bare,

but, in fact, I'm sitting in the middle of an immense, active colony of shearwaters.

The adults are out at sea, fishing,

but these are their burrows and inside almost every one,

there's a fat, juicy chick...

and THIS bird knows it.

This is a parrot, a kea.

Not the sort of parrot that is content with fruit and nut.

Its beak can certainly cope with such things,

but it can also give a bite that kills.

The keas tour the shearwaters' burrows, listening.

SQUEALS

They've heard something...

a shearwater chick is moving in its underground nest chamber.

But the tunnel is too narrow for them.

If they want the chick, they will have to dig for it.

Keas became meat-eaters relatively recently,

and have no special adaptations to help them find their victims.

Other birds who began to eat meat much earlier have very sophisticated ways of locating their targets.

The great grey owl hunts in the Arctic.

In summer, it hardly gets dark, but the owl's prey is largely invisible,

for it's hidden beneath the snow.

Like the kea, the owl listens for its victims.

But its hearing is many times more sensitive than the kea's, and ten times better than ours.

The feathered discs on either side of its face act like ear trumpets.

Each shields the ear on one side from sound coming from the other,

so the owl can scan the landscape in stereo.

It has detected a faint rustle beneath the snow -

made by a lemming.

Invisibility was insufficient protection for the lemming.

The great grey owl's amazing hearing enables it to hunt the year round,

even through the Arctic winter, when it's dark for weeks on end.

Elsewhere, other owls locate their prey with a different sense - vision.

The bigger the eye, the more light it gathers, so the better it functions at very low light levels.

These eyes are so big that they can't revolve in their sockets.

They belong to a scops owl.

They perceive shape not colour,

so a scops owl sees a soot and whitewash world,

a world that most other birds would find impenetrably dark.

Without colour,

it's movement that betrays the presence of prey.

A spider -

big enough and succulent enough to provide a snack for a scops.

And that is what it will be if it moves.

Daytime hunters, like these buzzards,

have vision of a different kind.

During the breeding season, they feed mainly on young rabbits.

If there is plenty of light,

an eye can become virtually a telescope

and buzzards can spot a rabbit from over a mile away...if it moves.

They also see it in full colour.

With such acute distant vision, a buzzard can survey a great area

without moving from its perch.

Rabbits feeding beside their warren.

They would be unwise to venture far from their holes.

The buzzard has detected a chance and is in the air.

From 300 feet above the ground, it can see each rabbit very clearly.

No luck this time - for the buzzard.

The great majority of a buzzard's attacks are failures,

but the energy spent on an attempt such as this was not great and the wind carries it back aloft.

The kestrel - little more than half the size of the buzzard.

It seeks much smaller prey - voles.

Its colour vision is also excellent - better than ours.

It spans more of the spectrum, extending into the ultraviolet,

so the blue of the sea around the Cornish coast appears more intense to a kestrel than it does to us.

For a long time, no-one understood how, or indeed IF, that might help it to hunt.

Now, we're beginning to get clues.

The voles a kestrel seeks

seldom leave the shelter of their tunnels in the grass during the day.

They mark their tracks with droplets of urine,

and urine, in ultraviolet light, is very conspicuous.

So with ultraviolet vision, the kestrel can SEE the signposts

that the voles can only smell.

As a consequence, the kestrel knows just where to focus its attention.

And that was a success.

The open skies above the wide plains of Africa.

Vultures.

They also eat meat, but only that which has been slaughtered by others.

They, too, rely on keen eyesight to find their meals.

Their eyes are so acute, they can keep watch over the plains from more than a thousand feet up.

The warm columns of air rising from the baking ground and captured by their broad wings

carries them up to great heights with little expenditure of energy

and supports them there.

They scan the ground beneath them,

but they also keep a sharp eye on one another.

A lappet-faced vulture is on the ground beside a carcass.

Griffon vultures have noticed it and have started to wheel downwards.

Others have already joined the lappet-faced around the kill.

As more birds glide down,

their descent is noticed from miles away in all directions.

And the news that a kill has been discovered

spreads across the network of watchers in the sky.

More and more start circling downwards towards the banquet.

Within a few minutes, the carcass is submerged beneath a dense scrum of struggling birds.

With no feathers on heads and necks, they do not unduly soil themselves

as they plunge their heads deep into the carcass.

And still more come.

The big cats may make most of the kills on the Serengeti,

but most of the meat on the plains is eaten, not by lions and leopards,

but by vultures.

To human nostrils, the stench of corruption here is overwhelming.

But these vultures are impervious to it. They can't sense it.

It was their sharp vision that brought them here.

But there's one bird that, exceptionally,

has an extremely acute sense of smell.

Here in the rain forest of Trinidad,

there is an almost unbroken ceiling of leaves above me.

No bird flying above that could possibly see a piece of meat like this lying on the forest floor.

But this is an extremely smelly piece of meat.

Let me...

hide it.

I can keep watch from a hill that rises above the canopy.

Not a bird in sight.

But there's one - a turkey vulture.

And another.

It's a turkey vulture because its head is not black like the other kind of vulture here, but red.

And it's always the turkey vultures that are on the scene first.

The meat I put down is directly under there,

and already - it's less than three-quarters of an hour ago - they are beginning to assemble.

It's almost unbelievable that the smell from that small piece of meat

could have drifted up through the canopy and so permeate the air

that it can be detected half a mile away,

and it's equally astonishing that the birds are able to measure its relative strength with such accuracy

that they can trace it back to its source simply by sensing in which direction it becomes stronger.

But the turkey vulture has wide-open nostrils

and extremely well-developed sense organs within them.

But it's getting close.

There's something in there somewhere.

Got it!

Their beaks are quite adequate for tearing off strips of flesh,

and vultures, after all, do not kill the animals that they eat.

But those that do must have much more powerful weapons.

Few animals can survive the grasp of these massive talons.

They belong to the African crowned eagle.

It is huge - nearly three feet long.

It can kill prey over four times its own weight.

It hunts over the East African forest and seeks, particularly, monkeys.

Vervet monkeys seldom expose themselves by venturing into the very highest branches,

so hunting them is not easy.

The eagle has relatively short wings for its great size,

which helps it to plunge through the canopy.

MONKEYS CALL

The vervets have a special call

that warns the whole troop that danger threatens.

It's caught a monkey.

Its mate joins it, and together, they return to their nest.

The chick is only a few days old,

too young to tear apart the prey for itself.

It has a lot of growing to do and a huge appetite.

The adults will have to feed it for four months before it can fly,

for nine months after that before it's strong enough to hunt itself.

To keep themselves properly fed, a pair of crowned eagles need a large hunting ground to themselves,

so all eagles defend their territories with great vigour.

This one, a sea eagle,

is patrolling a forested coast in Malaysia along which it fishes daily.

Those that live in the air have to fight in the air,

and eagles do so with their primary weapons - their talons.

Lake Bogoria in the African Rift Valley -

a soda lake fed by hot volcanic springs.

At first sight, a ferociously inhospitable place.

And it is - for most creatures.

But although no fish can live in its tepid soda-laden waters,

it is nonetheless packed with food for fish eagles.

A million flamingos.

Here, the food chain sustaining a meat-eater could scarcely be shorter.

Microscopic plants, algae, that can uniquely tolerate these salty waters

multiply in the sunshine by the ton.

Flamingos filter the algae from the water with their beaks - and vegetable is turned into flesh.

And that flesh is food for eagles.

The flamingos have to go into the shallows

to drink from a spring that provides the only fresh water in the lake.

But here they are very vulnerable.

As the eagle nears, the flamingos stampede into deeper water.

The eagle won't tackle them there

because it has difficulty carrying anything much bigger than a fish,

so it can only eat a flamingo in the shallows or on the shore.

This concentration of prey is so dense,

that pairs of fish eagles have been able to establish themselves every mile or so around the lake margins.

But even this number of hunters

has little effect on the size of the flamingo population.

Fish eagles normally snatch fish from the surface of the water,

they don't usually tackle a bird on the wing.

But there is no need to do so here.

Now it has to drag its victim to the shore.

Few hunters can have a greater concentration of prey

continuously at their disposal.

The flamingos are back in the shallows.

It would be difficult to imagine a more barren hunting territory

than this lava field in the volcanic islands of the Galapagos.

But there's a bird that finds its prey even here.

Although there is little vegetation on land,

there is a lot around the coast. And these marine iguanas graze on it.

They can even swim down to the sea bed to do so.

There they are unreachable by hunting birds.

But they come out of the sea onto the rocks to rest and to warm up.

The big ones are too big and strong for a hawk,

the small ones can scuttle away and hide in a crack,

but the females, at one time of the year, are vulnerable.

The Galapagos hawks know exactly when that is - the breeding season,

when the female iguanas go onto the few sandy beaches to lay their eggs.

Here, they can dig the holes they need.

Hawks all over the island keep watch beside the few beaches.

When the iguana has finished digging and laying, she must be tired,

so the hawk then has its best chance.

But even so, iguanas can run very fast indeed.

If the iguana can reach the rocks, she will be safe.

This one retreats into the burrow she has just dug.

She'll have to try and escape later.

The outcome is by no means certain - the iguana is still extremely strong.

But not strong enough.

A number of hawks take advantage of this bounty.

Wounded though it is, this one can still run.

The hawk has lost this encounter.

It can't catch an iguana once it has reached its burrow,

even though it might still be able to see it.

But some hawks are specially equipped

for snatching their prey from deep within holes.

This is the African harrier hawk.

Its legs are particularly long.

Crucially, they're double-jointed, so that they can bend backwards -

invaluable when groping in a nest hole, trying to extract a chick,

as this young bird is doing.

No luck.

But the adult, seeking lizards in the rocks, is more persistent.

It swallows its lizard whole.

This lizard, however, has been caught by a shrike -

a much smaller bird and too small to swallow such prey,

but neither its beak nor its claws are powerful enough to tear its victim's body apart.

The acacias of Africa provide all the hooks and spikes

that such a bird could need for butchery.

Prey as small as beetles and as big as stoats are treated this way.

Some of the larger animals are left on their skewers, like hung game,

so that decay loosens their flesh.

Stocks are sometimes built up

to last a shrike through hard times.

But often the temptation of fresh meat is irresistible.

The lammergeier actually eats bones,

but breaking up a large skeleton is an even bigger problem.

A lammergeier, hefty though it is,

has not got the beak or claws to do that job.

But, like the shrike, it knows a trick or two.

It doesn't just drop a bone anywhere.

It has its favourite patches of bare rock -

though sometimes its aim is not as good as it might be.

It's getting a few splinters off this bone.

It can swallow even the sharpest fragment,

for its powerfully acid digestive juices dissolve the bone rapidly.

The greatest prize is the marrow,

so the big bones have to be well and truly split,

and that takes perseverance.

A lammergeier may have to drop a bone up to 50 times before it hits rock at the right angle to split it.

The bodies of other animals provide such rich food

that a bird doesn't need much of it.

But getting it demands not only skill,

but often a great deal of effort.

An English wood is full of such food,

but the dense cover makes things difficult.

But there is one bird that specialises in hunting here.

It flies very fast, very low,

and takes its victims by surprise.

This is one of its favourite hunting places - an old overgrown orchard

where woodland birds feed on rotting apples, and the grubs they attract.

A sparrowhawk visits the wood every day

and waits for just the right moment.

It knows every twist and turn in its approach flight -

it has flown it often enough before, sometimes two or three times a day.

Its short rounded wings and long tail

enable it to fly at speed through really narrow gaps.

Warning calls alert the whole woodland.

ASSORTED BIRD CRIES

This time, it wasn't quick enough to catch the bird community by surprise.

This hunter is six times heavier than a sparrowhawk.

It's a goshawk and it hunts not only birds, but mammals.

A brown rat.

The goshawk, like the sparrowhawk, can manoeuvre through narrow gaps,

but it also has another way of hunting in the woodlands.

It will pursue the rat on foot.

Even though hunters have a formidable armoury and great skill,

most of their hunting trips, like this one, end in failure.

The coast of Cornwall -

territory of one of the most highly specialised of all hunting birds.

These are one of its favourite prey - pigeons.

High in the sky, so high it's almost invisible, a peregrine is watching.

Pigeons fly fast.

The peregrine starts its attack.

Wings drawn back, it's travelling at 200mph.

Striking its victim with its talons at this speed brings instant death.

The peregrine returns to its nest.

It has two eager customers for the meat.

An adult peregrine must kill several times a day

if its chicks are to be kept adequately fed.

Five weeks will pass before the chicks are fully fledged and ready for their first flight.

They start with experimental outings,

getting used to the feel of the air.

Another youngster watches.

Ten days later and the young birds are feeling confident enough to tease a passing seagull.

The high-speed aerial pounce - the peregrine's special killing tactic -

takes a lot of learning.

In mid-air, you must throw your legs forwards with talons outstretched...

and your sibling's tail makes a good practice target.

Now three youngsters join together in the game.

They perfect the manoeuvre that launches a dive -

the roll and the pumping of the wings with which the peregrine generates its unique speed.

Tumbling and rolling, diving and striking, it may seem like play,

but like so much play, it's practice for the serious business of adult life.

And now, a lesson for advanced students only.

An adult joins the youngsters carrying in its talons a pigeon - wounded but still alive.

And the youngster takes it to make its very first kill.

In a month, it will become the swiftest of all the world's hunters.

But only about a third of the earth is covered by land,

the rest is covered by water. There is plenty of food there, too,

but you have to learn different techniques to go fishing -

as we'll see in the next programme in The Life Of Birds.

Subtitles by Gillian Frazer BBC Scotland 1998