The Limits of Endurance The Life of Birds

*

The desolate wastes of the Antarctic -

so cold that insects would freeze solid.

Volcanic springs in Africa,

spouting water so hot and corrosive that it'll strip skin from flesh.

The waterless deserts of the tropics -

hundreds of square miles of baking sand.

The earth can be an inhospitable place,

yet birds of some kind manage somehow to endure all its privations.

Indeed, there is scarcely a corner of the globe that birds have not colonised.

Sandgrouse live in the deserts of Africa,

as barren a landscape as you can imagine.

Yet in these sands are tiny seeds,

shed by plants months or years ago after a storm briefly dampened the desert.

The sandgrouse, by searching incessantly, manage to pick out several thousand every day.

But they have to drink.

Waterholes are few and far between

and some birds may have to fly for as much as 50 miles to find one.

When they get there, all it is is a little puddle, like this one here.

SANDGROUSE CHIRP

After such a long flight, their thirst is huge.

But some must do more than satisfy their own needs.

They have left behind them, away in the desert, newly hatched chicks.

Chicks can't fly, but they too must have water and the males will take it to them.

They can't carry it in their crops.

They'll need that water to sustain themselves.

But they have extra tanks.

Their breast feathers have a special adaptation.

They're covered on the inner sides with filaments so fine that they absorb water like blotting paper.

And then they're off again on the long return flight.

A female is waiting for her mate.

It's roastingly hot

and with her are her chicks.

Here he comes... and the female makes way for him.

CHICKS TWITTER

While the last chick struggles from its shell,

the others cluster around and suck from his breast,

for all the world like puppies or kittens.

One comparatively small adaptation of its feathers

has enabled the sandgrouse to colonise a corner of the world closed to others.

The ground in the wake of one of the bush fires that regularly sweep across the grasslands of Africa

seems initially just as parched as its deserts.

Yet the courser, a relative of the plovers, is a nomad who actually seeks it out.

Insects, killed by the flames, are easily collected,

so it has some attractions.

Yet it is also here that it nests.

This must be a long-standing habit,

for its eggs are camouflaged to match the incinerated earth.

Since all the scrub has been cleared by fire,

the bird is able to see approaching predators.

Dawn on the shores of the Persian Gulf

and crab plovers, having fed on the edge of the sea,

come back to their breeding grounds.

It will soon be so hot that the sand will be painful to touch.

Yet this is where the crab plovers choose to nest.

Every other plover in the world lays its eggs in a simple scrape on the ground, but not these.

They, in spite of their unsuitably long legs,

have learned how to become burrowers.

A few inches below the surface, the sand is wonderfully cool.

A bird can sit on its eggs in comfort

throughout the crushing heat of the day.

To feed, the plovers have to go down to the edge of the sea.

There they can keep cool by bathing.

The African Rift Valley offers no such relief.

This steaming hot water comes from volcanic springs

and is so loaded with soda that around the lake it solidifies into white curds.

Yet flamingos come here in thousands.

The attraction? The salty, tepid water is full of algae and small crustaceans

which the birds collect using their specialised beaks like filter pumps.

The fact that so few creatures can tolerate these conditions

means that any animal that can has the place to itself

and can proliferate in vast numbers.

That applies to the crustaceans and the algae

and also to the birds that feed on them.

For the birds, there is an additional attraction.

The soda-rich waters are so caustic that hunters, such as hyenas or lions won't wade through them,

so the centre of the lake is one of the safest places for a nest.

The flamingos pile mud into mounds,

just high enough to be clear of any salt spray blown by the wind.

That, if it caked the eggs, would kill them.

But the heat is so extreme,

the congealed soda so caustic,

that sometimes a whole generation is lost.

Nonetheless, the success rate is still sufficient to maintain the size of the flocks.

This white desert is also hostile to life,

but for a very different reason.

The crust that I'm walking on is not soda, it's snow and ice,

and that too causes huge difficulties for birds.

Here in the Arctic during the winter,

such things as are edible are locked away beneath the snow and ice.

Nonetheless, a few birds manage to survive this bleak season provided they get help...

from polar bears.

The bears will eat almost every part of a seal, their staple diet,

but they leave enough to provide scavenging gulls with a meal.

In summer, on the tundra,

it's warm enough for plants to grow in the lakes.

There, spectacled eider duck swim and dive to collect insect larvae and worms from the muddy bottom.

But when winter comes, the lakes freeze and then the ducks vanish.

Until very recently, no-one knew where they went. The answer was found in 1995.

Hundreds of miles from the coast,

they gather together on the surface of the sea surrounded by ice.

There are no more than half a dozen such assemblies

and between them they contain the entire world population of the spectacled eider.

The birds are so tightly packed and so continuously on the move

that within their huge pond, the water does not freeze over.

They collect food from the bottom of the Arctic Ocean 200 feet below -

food that would otherwise be denied to them by the sea ice.

In the Antarctic, at the other end of the globe,

the winter can be even more severe.

Temperatures can fall to 80 degrees below zero and gales blow at over 100 miles an hour.

Yet this is the time the biggest penguins, emperors, HAVE to breed.

Having mated at the beginning of the winter,

the females return to the sea, leaving the eggs with the males,

who hold them on top of their feet to keep them off the ice.

Emperors are so big that there isn't time in the short Antarctic summer

for the chicks to grow into sea-going adults,

so breeding must start before the winter sets in.

The males cannot feed for four months.

Then the females will return, allowing the males to go down to the sea for a meal.

Meanwhile, in the continuous darkness of mid-winter,

broken only by the Southern Lights,

all the male emperors can do is endure.

The darkness perhaps doesn't trouble them unduly.

Penguins don't fly, but most birds DO and rely on sight to navigate,

so for them, darkness is a problem,

and no darkness is more complete than in a cave.

This is the Caripe Cavern, Venezuela.

BIRDS SCREECH

And here, there is no natural light whatsoever,

and yet, as I can hear from this deafening chorus of calls,

there's a huge population of birds here. How can they see to fly?

Well, we have with us some very, very dim lights and an extremely sensitive low-light camera.

So if I turn this out, I can't see anything at all

and presumably the birds can't either, but hopefully you can.

These are oilbirds. They're related to nightjars and like them have large eyes

that help them fly by the light of the moon and stars,

but in caves, even these are of no help.

Instead, the birds navigate by sound.

Their raucous social calls are augmented by high-pitched rattling sounds.

The echoes of these enable the birds to visualise their surroundings so well

that they can unfailingly find their own nest.

In the evening, they fly out into the comparative brightness of the starry sky to feed.

They seek out the fruit of palms and laurels

which have a strong fragrance, so the oilbirds can find them by smell.

They are now in no danger of being attacked by hawks,

as they would have been if they had not spent the day in the safety of their cave.

So all over the world, birds, by changing their habits or adapting their anatomy,

manage to survive in the most hostile of places.

A century ago, a new kind of environment appeared on earth

and nothing like it had faced birds before in their 200 million years' history,

yet some species began to adapt to it almost immediately.

This is it - the modern city.

Sao Paulo in Brazil, a wilderness of glass and brick, concrete and steel.

And circling among the skyscrapers - black vultures.

The ledges on these man-made cliffs serve as nest sites

and the vultures have little hesitation in using them.

DISHES CLATTER

MAN SPEAKS PORTUGUESE ON TV

This devoted parent has brought back a crop-load to feed its chicks.

The adults have little difficulty in finding all the food they need

for themselves and their young.

There is, literally, tons of it around.

A short flight away, on the city outskirts,

the rotting leftovers of a million meals are dumped daily,

mixed with inedible refuse of all kinds, some of it actively poisonous.

Not many birds have either the temperament to tolerate such places

or the digestion to cope with such food.

But those that have swarm in huge numbers,

like flamingos on an African soda lake.

In the same way, when farmers bring industrial methods into agriculture

and devote huge fields to raising just one particular crop

and it particularly suits the taste of one particular bird,

that bird will turn up in huge numbers to feast on it.

Waxwings.

They love these blueberries ripening in plantations in Florida,

so they come in thousands to collect them.

If they reach plague proportions,

then that is no more than a reflection of the intensive way in which man grows his crops.

Few other birds can manage to eat these large, cultivated blueberries

and indeed, even waxwings sometimes have a little trouble in doing so.

Crows have become highly skilled

at making a living in urban environments.

In this Japanese city, they have devised a way of eating a food that normally they can't manage.

Dropping a nut from a great height onto a road does sometimes crack it.

But some nuts are particularly tough,

so the crows have devised a better way.

Drop it among the traffic.

The problem now is collecting the bits without getting run over.

Some birds have refined their technique.

They station themselves beside pedestrian crossings.

Wait for the lights to stop the traffic.

BEEPING

Then collect your cracked nut in safety.

HORN HONKS

BELLS TOLL

City life may offer birds attractions that are rather less obvious than just food.

This is the centre of Glasgow - five o'clock on an autumn evening.

For half an hour, thousands of starlings put on a spectacular display of formation flying

over the darkening city.

WHY they do this we don't really know.

Maybe it is to get to know one another, creating a team spirit,

for they tend to spend the winter in parties.

Maybe it's because there's safety in numbers when avoiding predators.

When it's too dark for aerobatics, they come in to roost.

Such assemblies may be information centres.

Birds that have fed well head back to where they know there is food and those that are hungry will follow.

In Europe, towns are also attractive because it's warmer than out in the countryside.

You might think that this is the last place that a bird or any other animal would choose to sleep -

an oil refinery on the banks of the Amazon River in Central Brazil.

Just across the water, there's lovely, virgin rainforest,

yet here, well, just look and listen.

MECHANICAL CHURNING AND HISSING

A fine mist of acrid droplets stings your eyes.

The noise hurts your ears.

Yet promptly at five minutes past six o'clock every evening, there is an invasion.

'Purple martins. Stay still and they will settle within inches of you.'

Why they come here in such numbers is a mystery.

They can hardly be seeking warmth in this tropical Brazilian atmosphere.

They don't feed here.

Perhaps it's because there are fewer hawks to harry them than in the forest.

But whatever the reason, come they do.

In March, however, many of them will migrate north to the United States

to take up residence in very different homes.

AMERICAN VOICES CHATTER

RADIO: # Hey it's good to be back home again... #

A small lakeside town in Pennsylvania.

This luxury tower block has accommodation for over 40 adults and 200 youngsters.

Each apartment has all modern conveniences.

It can be wound down regularly by the local people

and the shelf brought out to make sure that the young are fit

and don't need any help with their housekeeping.

These apartments are so luxurious that these days purple martins don't nest in natural sites any more.

The purple martin has become totally dependent on human beings.

It's said that the tradition was started by the people native to this part of North America -

Choctaw and Chickasaw indians,

who were glad to see the birds arrive each spring

and hung out gourds to encourage them to nest.

Today, over a million people in the United States

offer hospitality to purple martins in this way.

It seems that those of us who live in cities feel increasingly cut off from the natural world

and so we treasure any contact we can find with wild creatures.

Certainly, an affection for birds is shared by all kinds and combinations of people all over the world.

In Arizona, Jesse Hendrix is particularly devoted to hummingbirds.

His home lies on the migration routes of several species.

The black-chinned is one of the most common.

In spring, they travel from Mexico on their way to nest as far north as Montana and British Columbia.

In autumn, he sees them again on their way back to their winter quarters in the warmth of the south.

Some of them have been fitted with leg rings,

so he knows that the same birds visit each year to drink from the same feeder.

It's possible that many now vary their routes to make sure that they visit such a reliable restaurant.

At the height of the migration, he may be visited in a single day by about 9,000 different birds

and every day he provides his customers with over 13 gallons of sugar water.

These meals could make the difference between life and death for the little rufous hummingbirds

which, on leaving Jesse's fuel station, have still to tackle the last stage of a 2,000-mile migration,

across the Bay of Mexico in one, single 600-mile non-stop flight.

The very regularity and predictability of birds can be part of their appeal.

..It's unpredictable. We can never be terribly certain...

On Philip Island, near Melbourne, Australia,

people come to watch a regular evening parade.

Little penguins - the smallest of the family.

They fish for pilchards and anchovies out at sea during the day

and every evening come ashore to return to their nest burrows,

following paths that have probably been in use for thousands of years.

Scientists started to tag them back in 1968.

It's the longest-running bird study in the whole of Australia,

so by now they are well used to being stared at.

Human beings have built houses for themselves along the penguins' beach,

but that hasn't deterred the birds.

Two half-grown chicks await their evening meal.

The human residents are only too delighted to have such engaging lodgers with regular habits

living beneath their front doorstep.

CHICKS SCREECH

Humanity's impact on the bird world has not always been so helpful.

Birds reached all the islands of the Pacific long before people did.

Small birds, such as white-eyes, are not very powerful flyers,

but probably made the sea crossings inadvertently, carried by storms.

Once on land, they and others,

like fantails, found insects to eat which doubtless had made the journey in the same sort of way.

Honeyeaters found plants in bloom from which they could drink nectar.

And pigeons found fruit.

But when people sailed across the sea,

they brought animals that by themselves could never have made the journey.

This is the small island of Guam

that during the Second World War became a major military base.

Some time in the 1940s,

brown tree snakes from New Guinea appeared here, brought by ships.

Tree snakes hunt birds

and Guam's white-eyes and fantails, having no experience of predators, had no defence against them.

Today, Guam is an island without birds.

Species that evolved here and differed from any elsewhere

have now gone for good.

Insects and spiders, without birds to keep them in check, have proliferated

and the forests have fallen totally silent.

These New Zealand forests have also been invaded by foreigners.

They have caused great problems for the kaka, the local parrot.

These invaders are surprisingly very small.

They are European wasps, but their effects have been devastating.

Kakas eat a great deal of vegetable food -

fruit and seeds and nectar.

But they also feast on honeydew,

a sticky fluid excreted by insects that live beneath the tree bark.

Female kakas rely on this high-energy food to bring them into breeding condition.

But the European wasps found honeydew much to their taste as well.

The kakas are unable to compete

and are already under attack from introduced predators such as stoats.

These insect invaders may well be the final competitors

that eliminate the kaka from these forests.

But the greatest destruction of the world's birds has been inflicted by human beings.

The huia, which once lived in New Zealand's woodlands,

was hunted precisely because it was rare and was finally totally gone in 1907.

The great auk, a giant, flightless relation of the razorbill,

was hunted and exterminated by the middle of the 19th century.

The dodo, a pigeon that, safe in its island sanctuary of Mauritius,

also evolved into a flightless giant,

was easy prey for sailors. They exterminated it by the middle of the 17th century,

less than 200 years after men first set foot on their island.

It's not only on islands that birds are vulnerable to changes brought by humanity.

150 years ago, prairies like this in the US

were home to flocks of birds two to three thousand MILLION strong.

They were so big they darkened the skies and took three days to pass.

They were probably the most numerous bird that has ever existed on earth -

passenger pigeons.

Their numbers were so astronomic that no-one considered them as anything but pests,

nor could imagine that they would ever be in danger of extinction.

But a combination of hunting and changes to the landscape brought by farming destroyed them.

The last wild passenger pigeon was sighted in 1889

and the last survivor of all, a lonely female called Martha,

died in Cincinnati Zoo in 1914.

Birds are still being slaughtered in huge numbers today,

particularly when there are economic reasons for doing so.

Dickcissels in Venezuela also swarm in flocks millions strong.

The whole world's population comes here in winter, sometimes roosting in only three or four sites.

Should anything happen to those sites, the dickcissels could go the same way as the passenger pigeon,

and they are a very serious pest.

Farmers know how to deal with INSECT pests.

They spray them with poisons.

So the same technique is sometimes used against dickcissels,

in spite of the fact that it's against the law.

The birds, recorded here by amateur video,

take several days to die.

Yet humanity, so often in the past the mindless and merciless exterminator of birds,

can sometimes become their guardians.

In West Africa, in Cameroon, villagers celebrate the forest beside which they live

and in particular one of its birds.

Bannerman's turaco.

Many of the creatures of the forest, such as the elephant, that also feature in this celebration,

have long since disappeared.

The turaco, however, still survives,

though in this forest there are only about 4,000 pairs

and it lives nowhere else.

For decades, the forest has been felled to make way for fields in which the people can grow their food.

It's now only half the size it was 30 years ago.

Yet the people also know that they depend on the forest -

for water and firewood, for medicine and for meat.

So now a balance has been struck.

The traditional beliefs of the people have been harnessed to come to the forest's defence.

The masked figure of Mabu, their spirit guardian, accompanied by the village elders,

regularly patrols the margins of the forest.

Stakes are planted to mark the point beyond which no tree may be felled.

The turaco has become a symbol of the villagers' regard for their environment.

Mabu is in league with international bird conservation bodies

who are also concerned about the survival of Bannerman's turaco.

MAN PURRS AND WHOOPS

In North America, there are other masquerades to protect a bird that is even rarer than the turaco.

A whooping crane chick learns to feed, encouraged by the gestures and calls of human foster parents.

In 1945, only 16 whooping cranes existed.

Today, there are 300,

thanks to captive breeding and the patient rearing of chicks by hand.

And this is surely one of the most extraordinary hand-rearing devices yet invented -

a whooping crane adult glove puppet,

with a trigger inside so that I can operate the beak.

I'm speaking quietly because behind these doors are whooping crane chicks

and it's important they don't get used to the sound of human voices

at this early stage in their lives.

It's even more important that they don't SEE humans, which is why they're fed with this.

Here at the International Crane Foundation in Wisconsin,

they believe that were the chicks fed by humans directly and visibly, they'd risk becoming humanised,

so that as adults, they wouldn't be able to breed with their own kind.

As they grow, the whoopers lose all their brown plumage

and replace it with white feathers.

They must now learn how to use them in flight.

And once again, they have to be shown the sort of thing they must do.

Away to the west, in Idaho,

a farmer with a passion for cranes, Kent Clegg, has also been rearing a small group of chicks.

He has a mechanised way of persuading his little flock to fly.

He has reared them in a quite different way -

initially in small groups, which he believes will avoid humanisation.

He then taught them to follow him.

He's put them together with the young of a commoner, smaller species, sandhill cranes, the all-brown ones.

So the little mixed flock has become confident in the air.

There's one further problem - whooping cranes are migratory.

In the past, some used to overwinter in the US, but many, in the autumn, would fly south to New Mexico.

These birds might try to do the same thing,

but how would they know which way to go without their parents to guide them?

Well, that problem is being tackled too.

Kent Clegg is planning to lead them there himself in his microlight.

Birds were flying from continent to continent long before we were.

They reached the coldest place on earth long before we did.

They can survive in the deserts.

Some can remain on the wing for years at a time.

Now we have taken over the earth and the sea and the sky,

but with skill, care and knowledge

we can ensure that there is still a place on earth for birds

in all their beauty and variety...

if we want to... and surely we should.

Subtitles by Neil Gemmill BBC Scotland - 1998