The Life of Birds (1998) s01e04 Episode Script

Sparrows in South Africa.
Like all sparrows, they eat pretty well anything; insects, fruit and particularly seeds.
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 there's plenty of time for sitting around on the perch.
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 at the moment are out at sea fishing, but these are their burrows and inside of almost every one, there is a fat, juicy chick.
And this bird knows it.
This is a parrot, a kea, but not the sort of parrot that is content just with fruit and nuts.
Its beak can certainly cope with such things, but it can also give a bite that kills.
The keas tour the shearwaters' burrows, listening.
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.
But other birds took to eating meat much earlier and they have some highly sophisticated ways of locating their targets.
The great grey owl hunts in the Arctic.
In the summer, it scarcely gets dark, but the owl's prey is, in any case, largely invisible for it is hidden beneath the snow.
Like the kea, the owl listens for its victims.
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's detected a faint rustle beneath the snow, made by a lemming.
Invisibility was insufficient protection for the lemming.
The great grey owl's 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 an 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 even revolve in their sockets.
They belong to a scops owl They are sensitive to shape rather than colour, so a scops owl sees a soot and whitewash world, but a world that most other birds would find impenetrably dark.
Without colour, it's movement that betrays the presence of prey.
A spider.
Quite 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 keep a great area under constant surveillance 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, indeed, than ours for it spans a greater range of the spectrum extending into the ultraviolet.
So the blue of the sea around the Cornish coast appears much more intense to a kestrel than it does to us.
For a long time, no one could understand how, or indeed if, that might help it to hunt.
Now we're beginning to get clues.
The voles seldom leave the shelter of their tunnels through the grass, at least during the day.
They repeatedly mark their tracks with 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 1,000 feet up.
The warm columns of air rising from the baking ground and captured by their broad wings carries them up with very little expenditure of energy on their part 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.
0thers 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 as each bird reacts, 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.
Lacking feathers on their 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 produced on the plains is consumed, 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 the sharpness of their vision that brought them here.
But there's one bird that, exceptionally, has en extremely acute sense of smell.
Here in the rainforest of Trinidad there's an almost unbroken ceiling of leaves above me.
No bird flying in the sky above could 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 vultureand another.
You can tell it's a turkey vulture, because its naked head is not black 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're beginning to assemble.
It seems almost unbelievable that the smell from that small piece of meat could have drifted up through the forest canopy and so permeate the air that it can be detected half a mile away.
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 marginally stronger.
But a turkey vulture is exceptionally well-equipped among birds; with wide-open nostrils and extremely well-developed sense organs within them.
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 have to have much more powerful weapons.
Few animals can survive the grasp of these massive talons.
They belong to the African crowned eagle.
This bird is huge, over three feet long, and it can kill prey over four times its own weight.
It hunts over the canopy of 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 if it has to plunge through the canopy.
The vervets have a special call that warns the whole troop that danger threatens from above.
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 is ready to fly from the nest, and nine months after that before it is strong enough to hunt for itself.
To keep themselves and their young properly fed, a pair of crowned eagles need a large hunting ground all to themselves.
So all eagles defend their territories with great vigour.
This one, a sea eagle, is patrolling a forest-covered coast in Malaysia along which it fishes every day.
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 indeed it is, for most creatures.
But although no fish can live in its tepid soda-laden waters, it's nonetheless packed with food for fish eagles.
A million flamingos.
The food chain that sustains a meat-eater could scarcely be shorter than it is here.
Microscopic plants, algae, that can uniquely tolerate these salty waters proliferate 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 the spring that provides the only fresh water in the lake.
But here they are very vulnerable.
As the eagle approaches, the flamingos stampede into deeper water.
The eagle won't tackle them there because it has difficulty in lifting anything much bigger than a fish and carrying it away.
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 margins of the lake.
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 quite a lot in the waters around the coast.
And these bizarre lizards, marine iguanas, graze on it.
They can even swim to the sea-floor to do so.
There they are unreachable by hunting birds.
But they come out of the sea on to 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 get safety in one of the cracks.
But the females, particularly at one time of the year, are vulnerable.
The Galapagos hawks know exactly when that is.
It's the breeding season, when the female iguanas must venture out on to 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.
By the time 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'll be safe.
This one retreats into the burrow she's only just dug.
She'll have to try and make her 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 especially equipped for snatching their prey from deep within holes.
This is the African harrier hawk.
Its legs are particularly long.
Even more crucially, they are double-jointed, so they can bend backwards, invaluable when groping in the depths of 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 in these larders 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 a 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 digestive juices are so powerfully acid that bone dissolves very rapidly.
The greatest prize is the marrow and to get that, 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 just the right angle to split it.
The bodies of other animals provide such rich food that a bird doesn't need to eat a lot of it.
But getting it nonetheless 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 lots of woodland birds come to 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.
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 too can manoeuvre through the 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, the 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 200 miles an hour.
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 must pass before the chicks are fully fledged and ready for their first flight.
They start with somewhat experimental outings, getting used to the feel of the air in their wings.
Another youngster watches.
Ten days later the young birds are confident enough to tease a passing seagull.
The high-speed aerial pounce, the peregrine's speciality, takes a lot of learning.
You have to be able, in mid-air, to throw your legs forwards with talons outstretched.
Your sibling's tail makes a good practice target.
Now three youngsters join together in the game.
They perfect the manoeuvre that launches the 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 innocent 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 joining 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, of one kind or another.
There's plenty of food there, too, but you have to learn very different techniques if you're going to go fishing, as we will see in the next programme in The Life 0f Birds.