0:00:02 > 0:00:07*
0:00:35 > 0:00:38The desolate wastes of the Antarctic -
0:00:38 > 0:00:42so cold that insects would freeze solid.
0:00:43 > 0:00:46Volcanic springs in Africa,
0:00:46 > 0:00:51spouting water so hot and corrosive that it'll strip skin from flesh.
0:00:53 > 0:00:57The waterless deserts of the tropics -
0:00:57 > 0:01:00hundreds of square miles of baking sand.
0:01:03 > 0:01:07The earth can be an inhospitable place,
0:01:07 > 0:01:13yet birds of some kind manage somehow to endure all its privations.
0:01:13 > 0:01:19Indeed, there is scarcely a corner of the globe that birds have not colonised.
0:01:27 > 0:01:30Sandgrouse live in the deserts of Africa,
0:01:30 > 0:01:34as barren a landscape as you can imagine.
0:01:34 > 0:01:37Yet in these sands are tiny seeds,
0:01:37 > 0:01:43shed by plants months or years ago after a storm briefly dampened the desert.
0:01:43 > 0:01:50The sandgrouse, by searching incessantly, manage to pick out several thousand every day.
0:01:51 > 0:01:54But they have to drink.
0:01:54 > 0:01:57Waterholes are few and far between
0:01:57 > 0:02:02and some birds may have to fly for as much as 50 miles to find one.
0:02:02 > 0:02:08When they get there, all it is is a little puddle, like this one here.
0:02:08 > 0:02:11SANDGROUSE CHIRP
0:02:16 > 0:02:20After such a long flight, their thirst is huge.
0:02:52 > 0:02:57But some must do more than satisfy their own needs.
0:02:57 > 0:03:02They have left behind them, away in the desert, newly hatched chicks.
0:03:02 > 0:03:09Chicks can't fly, but they too must have water and the males will take it to them.
0:03:09 > 0:03:12They can't carry it in their crops.
0:03:12 > 0:03:16They'll need that water to sustain themselves.
0:03:16 > 0:03:19But they have extra tanks.
0:03:19 > 0:03:23Their breast feathers have a special adaptation.
0:03:23 > 0:03:31They're covered on the inner sides with filaments so fine that they absorb water like blotting paper.
0:03:35 > 0:03:40And then they're off again on the long return flight.
0:03:46 > 0:03:48A female is waiting for her mate.
0:03:48 > 0:03:51It's roastingly hot
0:03:51 > 0:03:54and with her are her chicks.
0:03:57 > 0:04:01Here he comes... and the female makes way for him.
0:04:06 > 0:04:09CHICKS TWITTER
0:04:09 > 0:04:13While the last chick struggles from its shell,
0:04:13 > 0:04:18the others cluster around and suck from his breast,
0:04:18 > 0:04:21for all the world like puppies or kittens.
0:04:23 > 0:04:28One comparatively small adaptation of its feathers
0:04:28 > 0:04:34has enabled the sandgrouse to colonise a corner of the world closed to others.
0:04:37 > 0:04:45The ground in the wake of one of the bush fires that regularly sweep across the grasslands of Africa
0:04:45 > 0:04:49seems initially just as parched as its deserts.
0:04:49 > 0:04:56Yet the courser, a relative of the plovers, is a nomad who actually seeks it out.
0:04:56 > 0:05:00Insects, killed by the flames, are easily collected,
0:05:00 > 0:05:03so it has some attractions.
0:05:03 > 0:05:06Yet it is also here that it nests.
0:05:11 > 0:05:14This must be a long-standing habit,
0:05:14 > 0:05:19for its eggs are camouflaged to match the incinerated earth.
0:05:19 > 0:05:23Since all the scrub has been cleared by fire,
0:05:23 > 0:05:27the bird is able to see approaching predators.
0:05:38 > 0:05:42Dawn on the shores of the Persian Gulf
0:05:42 > 0:05:48and crab plovers, having fed on the edge of the sea,
0:05:48 > 0:05:50come back to their breeding grounds.
0:05:50 > 0:05:56It will soon be so hot that the sand will be painful to touch.
0:05:56 > 0:06:01Yet this is where the crab plovers choose to nest.
0:06:06 > 0:06:13Every other plover in the world lays its eggs in a simple scrape on the ground, but not these.
0:06:13 > 0:06:17They, in spite of their unsuitably long legs,
0:06:17 > 0:06:20have learned how to become burrowers.
0:06:20 > 0:06:25A few inches below the surface, the sand is wonderfully cool.
0:06:25 > 0:06:29A bird can sit on its eggs in comfort
0:06:29 > 0:06:33throughout the crushing heat of the day.
0:06:36 > 0:06:41To feed, the plovers have to go down to the edge of the sea.
0:06:45 > 0:06:49There they can keep cool by bathing.
0:07:02 > 0:07:06The African Rift Valley offers no such relief.
0:07:06 > 0:07:10This steaming hot water comes from volcanic springs
0:07:10 > 0:07:17and is so loaded with soda that around the lake it solidifies into white curds.
0:07:17 > 0:07:20Yet flamingos come here in thousands.
0:07:25 > 0:07:32The attraction? The salty, tepid water is full of algae and small crustaceans
0:07:32 > 0:07:37which the birds collect using their specialised beaks like filter pumps.
0:07:41 > 0:07:46The fact that so few creatures can tolerate these conditions
0:07:46 > 0:07:50means that any animal that can has the place to itself
0:07:50 > 0:07:53and can proliferate in vast numbers.
0:07:53 > 0:07:57That applies to the crustaceans and the algae
0:07:57 > 0:08:01and also to the birds that feed on them.
0:08:01 > 0:08:05For the birds, there is an additional attraction.
0:08:05 > 0:08:12The soda-rich waters are so caustic that hunters, such as hyenas or lions won't wade through them,
0:08:12 > 0:08:18so the centre of the lake is one of the safest places for a nest.
0:08:26 > 0:08:28The flamingos pile mud into mounds,
0:08:28 > 0:08:33just high enough to be clear of any salt spray blown by the wind.
0:08:33 > 0:08:37That, if it caked the eggs, would kill them.
0:08:41 > 0:08:44But the heat is so extreme,
0:08:44 > 0:08:46the congealed soda so caustic,
0:08:46 > 0:08:50that sometimes a whole generation is lost.
0:08:50 > 0:08:57Nonetheless, the success rate is still sufficient to maintain the size of the flocks.
0:09:05 > 0:09:10This white desert is also hostile to life,
0:09:10 > 0:09:13but for a very different reason.
0:09:14 > 0:09:20The crust that I'm walking on is not soda, it's snow and ice,
0:09:20 > 0:09:24and that too causes huge difficulties for birds.
0:09:24 > 0:09:28Here in the Arctic during the winter,
0:09:28 > 0:09:33such things as are edible are locked away beneath the snow and ice.
0:09:33 > 0:09:40Nonetheless, a few birds manage to survive this bleak season provided they get help...
0:09:40 > 0:09:43from polar bears.
0:09:53 > 0:09:58The bears will eat almost every part of a seal, their staple diet,
0:09:58 > 0:10:04but they leave enough to provide scavenging gulls with a meal.
0:10:23 > 0:10:26In summer, on the tundra,
0:10:26 > 0:10:30it's warm enough for plants to grow in the lakes.
0:10:30 > 0:10:38There, spectacled eider duck swim and dive to collect insect larvae and worms from the muddy bottom.
0:10:50 > 0:10:55But when winter comes, the lakes freeze and then the ducks vanish.
0:10:55 > 0:11:02Until very recently, no-one knew where they went. The answer was found in 1995.
0:11:02 > 0:11:04Hundreds of miles from the coast,
0:11:04 > 0:11:10they gather together on the surface of the sea surrounded by ice.
0:11:14 > 0:11:18There are no more than half a dozen such assemblies
0:11:18 > 0:11:25and between them they contain the entire world population of the spectacled eider.
0:11:36 > 0:11:41The birds are so tightly packed and so continuously on the move
0:11:41 > 0:11:46that within their huge pond, the water does not freeze over.
0:11:46 > 0:11:52They collect food from the bottom of the Arctic Ocean 200 feet below -
0:11:52 > 0:11:57food that would otherwise be denied to them by the sea ice.
0:12:00 > 0:12:05In the Antarctic, at the other end of the globe,
0:12:05 > 0:12:07the winter can be even more severe.
0:12:07 > 0:12:14Temperatures can fall to 80 degrees below zero and gales blow at over 100 miles an hour.
0:12:14 > 0:12:20Yet this is the time the biggest penguins, emperors, HAVE to breed.
0:12:22 > 0:12:26Having mated at the beginning of the winter,
0:12:26 > 0:12:32the females return to the sea, leaving the eggs with the males,
0:12:32 > 0:12:37who hold them on top of their feet to keep them off the ice.
0:12:39 > 0:12:45Emperors are so big that there isn't time in the short Antarctic summer
0:12:45 > 0:12:49for the chicks to grow into sea-going adults,
0:12:49 > 0:12:53so breeding must start before the winter sets in.
0:13:01 > 0:13:05The males cannot feed for four months.
0:13:05 > 0:13:11Then the females will return, allowing the males to go down to the sea for a meal.
0:13:17 > 0:13:22Meanwhile, in the continuous darkness of mid-winter,
0:13:22 > 0:13:25broken only by the Southern Lights,
0:13:25 > 0:13:29all the male emperors can do is endure.
0:13:31 > 0:13:35The darkness perhaps doesn't trouble them unduly.
0:13:35 > 0:13:41Penguins don't fly, but most birds DO and rely on sight to navigate,
0:13:41 > 0:13:44so for them, darkness is a problem,
0:13:44 > 0:13:49and no darkness is more complete than in a cave.
0:13:49 > 0:13:52This is the Caripe Cavern, Venezuela.
0:13:52 > 0:13:54BIRDS SCREECH
0:13:54 > 0:13:59And here, there is no natural light whatsoever,
0:13:59 > 0:14:04and yet, as I can hear from this deafening chorus of calls,
0:14:04 > 0:14:09there's a huge population of birds here. How can they see to fly?
0:14:09 > 0:14:17Well, we have with us some very, very dim lights and an extremely sensitive low-light camera.
0:14:17 > 0:14:22So if I turn this out, I can't see anything at all
0:14:22 > 0:14:28and presumably the birds can't either, but hopefully you can.
0:14:30 > 0:14:36These are oilbirds. They're related to nightjars and like them have large eyes
0:14:36 > 0:14:41that help them fly by the light of the moon and stars,
0:14:41 > 0:14:45but in caves, even these are of no help.
0:14:45 > 0:14:47Instead, the birds navigate by sound.
0:14:47 > 0:14:54Their raucous social calls are augmented by high-pitched rattling sounds.
0:14:54 > 0:15:00The echoes of these enable the birds to visualise their surroundings so well
0:15:00 > 0:15:05that they can unfailingly find their own nest.
0:15:06 > 0:15:13In the evening, they fly out into the comparative brightness of the starry sky to feed.
0:15:15 > 0:15:20They seek out the fruit of palms and laurels
0:15:20 > 0:15:25which have a strong fragrance, so the oilbirds can find them by smell.
0:15:28 > 0:15:32They are now in no danger of being attacked by hawks,
0:15:32 > 0:15:39as they would have been if they had not spent the day in the safety of their cave.
0:15:56 > 0:16:02So all over the world, birds, by changing their habits or adapting their anatomy,
0:16:02 > 0:16:06manage to survive in the most hostile of places.
0:16:08 > 0:16:12A century ago, a new kind of environment appeared on earth
0:16:12 > 0:16:19and nothing like it had faced birds before in their 200 million years' history,
0:16:19 > 0:16:23yet some species began to adapt to it almost immediately.
0:16:23 > 0:16:26This is it - the modern city.
0:16:28 > 0:16:34Sao Paulo in Brazil, a wilderness of glass and brick, concrete and steel.
0:16:34 > 0:16:39And circling among the skyscrapers - black vultures.
0:16:39 > 0:16:44The ledges on these man-made cliffs serve as nest sites
0:16:44 > 0:16:49and the vultures have little hesitation in using them.
0:16:49 > 0:16:51DISHES CLATTER
0:16:51 > 0:16:54MAN SPEAKS PORTUGUESE ON TV
0:17:06 > 0:17:11This devoted parent has brought back a crop-load to feed its chicks.
0:17:30 > 0:17:35The adults have little difficulty in finding all the food they need
0:17:35 > 0:17:38for themselves and their young.
0:17:40 > 0:17:44There is, literally, tons of it around.
0:18:01 > 0:18:05A short flight away, on the city outskirts,
0:18:05 > 0:18:09the rotting leftovers of a million meals are dumped daily,
0:18:09 > 0:18:15mixed with inedible refuse of all kinds, some of it actively poisonous.
0:18:15 > 0:18:20Not many birds have either the temperament to tolerate such places
0:18:20 > 0:18:24or the digestion to cope with such food.
0:18:24 > 0:18:28But those that have swarm in huge numbers,
0:18:28 > 0:18:31like flamingos on an African soda lake.
0:18:41 > 0:18:47In the same way, when farmers bring industrial methods into agriculture
0:18:47 > 0:18:52and devote huge fields to raising just one particular crop
0:18:52 > 0:18:56and it particularly suits the taste of one particular bird,
0:18:56 > 0:19:01that bird will turn up in huge numbers to feast on it.
0:19:02 > 0:19:05Waxwings.
0:19:08 > 0:19:13They love these blueberries ripening in plantations in Florida,
0:19:13 > 0:19:17so they come in thousands to collect them.
0:19:17 > 0:19:20If they reach plague proportions,
0:19:20 > 0:19:27then that is no more than a reflection of the intensive way in which man grows his crops.
0:19:27 > 0:19:33Few other birds can manage to eat these large, cultivated blueberries
0:19:33 > 0:19:38and indeed, even waxwings sometimes have a little trouble in doing so.
0:19:50 > 0:19:53Crows have become highly skilled
0:19:53 > 0:19:56at making a living in urban environments.
0:19:56 > 0:20:04In this Japanese city, they have devised a way of eating a food that normally they can't manage.
0:20:22 > 0:20:28Dropping a nut from a great height onto a road does sometimes crack it.
0:20:28 > 0:20:31But some nuts are particularly tough,
0:20:31 > 0:20:35so the crows have devised a better way.
0:20:41 > 0:20:44Drop it among the traffic.
0:20:58 > 0:21:04The problem now is collecting the bits without getting run over.
0:21:08 > 0:21:12Some birds have refined their technique.
0:21:12 > 0:21:16They station themselves beside pedestrian crossings.
0:21:32 > 0:21:36Wait for the lights to stop the traffic.
0:21:38 > 0:21:40BEEPING
0:21:45 > 0:21:50Then collect your cracked nut in safety.
0:21:55 > 0:21:59HORN HONKS
0:22:03 > 0:22:06BELLS TOLL
0:22:06 > 0:22:12City life may offer birds attractions that are rather less obvious than just food.
0:22:12 > 0:22:18This is the centre of Glasgow - five o'clock on an autumn evening.
0:22:18 > 0:22:25For half an hour, thousands of starlings put on a spectacular display of formation flying
0:22:25 > 0:22:27over the darkening city.
0:22:29 > 0:22:33WHY they do this we don't really know.
0:22:33 > 0:22:39Maybe it is to get to know one another, creating a team spirit,
0:22:39 > 0:22:42for they tend to spend the winter in parties.
0:22:42 > 0:22:47Maybe it's because there's safety in numbers when avoiding predators.
0:22:50 > 0:22:55When it's too dark for aerobatics, they come in to roost.
0:22:55 > 0:22:59Such assemblies may be information centres.
0:22:59 > 0:23:07Birds that have fed well head back to where they know there is food and those that are hungry will follow.
0:23:07 > 0:23:13In Europe, towns are also attractive because it's warmer than out in the countryside.
0:23:19 > 0:23:26You might think that this is the last place that a bird or any other animal would choose to sleep -
0:23:26 > 0:23:32an oil refinery on the banks of the Amazon River in Central Brazil.
0:23:32 > 0:23:37Just across the water, there's lovely, virgin rainforest,
0:23:37 > 0:23:41yet here, well, just look and listen.
0:23:41 > 0:23:44MECHANICAL CHURNING AND HISSING
0:23:44 > 0:23:49A fine mist of acrid droplets stings your eyes.
0:23:49 > 0:23:51The noise hurts your ears.
0:23:54 > 0:24:01Yet promptly at five minutes past six o'clock every evening, there is an invasion.
0:24:09 > 0:24:15'Purple martins. Stay still and they will settle within inches of you.'
0:24:22 > 0:24:26Why they come here in such numbers is a mystery.
0:24:26 > 0:24:32They can hardly be seeking warmth in this tropical Brazilian atmosphere.
0:24:32 > 0:24:34They don't feed here.
0:24:34 > 0:24:41Perhaps it's because there are fewer hawks to harry them than in the forest.
0:24:41 > 0:24:45But whatever the reason, come they do.
0:24:46 > 0:24:52In March, however, many of them will migrate north to the United States
0:24:52 > 0:24:56to take up residence in very different homes.
0:24:58 > 0:25:01AMERICAN VOICES CHATTER
0:25:01 > 0:25:09RADIO: # Hey it's good to be back home again... #
0:25:14 > 0:25:17A small lakeside town in Pennsylvania.
0:25:35 > 0:25:42This luxury tower block has accommodation for over 40 adults and 200 youngsters.
0:25:42 > 0:25:46Each apartment has all modern conveniences.
0:25:46 > 0:25:51It can be wound down regularly by the local people
0:25:51 > 0:25:56and the shelf brought out to make sure that the young are fit
0:25:56 > 0:25:59and don't need any help with their housekeeping.
0:25:59 > 0:26:07These apartments are so luxurious that these days purple martins don't nest in natural sites any more.
0:26:07 > 0:26:12The purple martin has become totally dependent on human beings.
0:26:28 > 0:26:35It's said that the tradition was started by the people native to this part of North America -
0:26:35 > 0:26:38Choctaw and Chickasaw indians,
0:26:38 > 0:26:42who were glad to see the birds arrive each spring
0:26:42 > 0:26:46and hung out gourds to encourage them to nest.
0:26:46 > 0:26:51Today, over a million people in the United States
0:26:51 > 0:26:55offer hospitality to purple martins in this way.
0:26:55 > 0:27:03It seems that those of us who live in cities feel increasingly cut off from the natural world
0:27:03 > 0:27:08and so we treasure any contact we can find with wild creatures.
0:27:08 > 0:27:16Certainly, an affection for birds is shared by all kinds and combinations of people all over the world.
0:27:24 > 0:27:30In Arizona, Jesse Hendrix is particularly devoted to hummingbirds.
0:27:37 > 0:27:42His home lies on the migration routes of several species.
0:27:42 > 0:27:46The black-chinned is one of the most common.
0:27:46 > 0:27:54In spring, they travel from Mexico on their way to nest as far north as Montana and British Columbia.
0:27:54 > 0:28:02In autumn, he sees them again on their way back to their winter quarters in the warmth of the south.
0:28:07 > 0:28:11Some of them have been fitted with leg rings,
0:28:11 > 0:28:17so he knows that the same birds visit each year to drink from the same feeder.
0:28:17 > 0:28:25It's possible that many now vary their routes to make sure that they visit such a reliable restaurant.
0:28:31 > 0:28:38At the height of the migration, he may be visited in a single day by about 9,000 different birds
0:28:38 > 0:28:45and every day he provides his customers with over 13 gallons of sugar water.
0:28:45 > 0:28:52These meals could make the difference between life and death for the little rufous hummingbirds
0:28:52 > 0:28:59which, on leaving Jesse's fuel station, have still to tackle the last stage of a 2,000-mile migration,
0:28:59 > 0:29:05across the Bay of Mexico in one, single 600-mile non-stop flight.
0:29:09 > 0:29:16The very regularity and predictability of birds can be part of their appeal.
0:29:16 > 0:29:21..It's unpredictable. We can never be terribly certain...
0:29:21 > 0:29:24On Philip Island, near Melbourne, Australia,
0:29:24 > 0:29:29people come to watch a regular evening parade.
0:29:29 > 0:29:33Little penguins - the smallest of the family.
0:29:58 > 0:30:03They fish for pilchards and anchovies out at sea during the day
0:30:03 > 0:30:08and every evening come ashore to return to their nest burrows,
0:30:08 > 0:30:14following paths that have probably been in use for thousands of years.
0:30:23 > 0:30:28Scientists started to tag them back in 1968.
0:30:28 > 0:30:33It's the longest-running bird study in the whole of Australia,
0:30:33 > 0:30:37so by now they are well used to being stared at.
0:30:49 > 0:30:55Human beings have built houses for themselves along the penguins' beach,
0:30:55 > 0:30:58but that hasn't deterred the birds.
0:31:08 > 0:31:12Two half-grown chicks await their evening meal.
0:31:12 > 0:31:19The human residents are only too delighted to have such engaging lodgers with regular habits
0:31:19 > 0:31:22living beneath their front doorstep.
0:31:22 > 0:31:24CHICKS SCREECH
0:31:46 > 0:31:52Humanity's impact on the bird world has not always been so helpful.
0:31:52 > 0:31:58Birds reached all the islands of the Pacific long before people did.
0:31:58 > 0:32:03Small birds, such as white-eyes, are not very powerful flyers,
0:32:03 > 0:32:09but probably made the sea crossings inadvertently, carried by storms.
0:32:09 > 0:32:12Once on land, they and others,
0:32:12 > 0:32:20like fantails, found insects to eat which doubtless had made the journey in the same sort of way.
0:32:20 > 0:32:25Honeyeaters found plants in bloom from which they could drink nectar.
0:32:33 > 0:32:36And pigeons found fruit.
0:32:47 > 0:32:51But when people sailed across the sea,
0:32:51 > 0:32:57they brought animals that by themselves could never have made the journey.
0:32:57 > 0:33:00This is the small island of Guam
0:33:00 > 0:33:06that during the Second World War became a major military base.
0:33:06 > 0:33:09Some time in the 1940s,
0:33:09 > 0:33:15brown tree snakes from New Guinea appeared here, brought by ships.
0:33:15 > 0:33:18Tree snakes hunt birds
0:33:18 > 0:33:25and Guam's white-eyes and fantails, having no experience of predators, had no defence against them.
0:33:38 > 0:33:42Today, Guam is an island without birds.
0:33:42 > 0:33:47Species that evolved here and differed from any elsewhere
0:33:47 > 0:33:49have now gone for good.
0:33:49 > 0:33:55Insects and spiders, without birds to keep them in check, have proliferated
0:33:55 > 0:34:00and the forests have fallen totally silent.
0:34:10 > 0:34:15These New Zealand forests have also been invaded by foreigners.
0:34:15 > 0:34:21They have caused great problems for the kaka, the local parrot.
0:34:21 > 0:34:25These invaders are surprisingly very small.
0:34:25 > 0:34:30They are European wasps, but their effects have been devastating.
0:34:35 > 0:34:39Kakas eat a great deal of vegetable food -
0:34:39 > 0:34:42fruit and seeds and nectar.
0:34:43 > 0:34:46But they also feast on honeydew,
0:34:46 > 0:34:51a sticky fluid excreted by insects that live beneath the tree bark.
0:34:51 > 0:34:58Female kakas rely on this high-energy food to bring them into breeding condition.
0:35:03 > 0:35:08But the European wasps found honeydew much to their taste as well.
0:35:11 > 0:35:13The kakas are unable to compete
0:35:13 > 0:35:19and are already under attack from introduced predators such as stoats.
0:35:28 > 0:35:32These insect invaders may well be the final competitors
0:35:32 > 0:35:36that eliminate the kaka from these forests.
0:35:36 > 0:35:43But the greatest destruction of the world's birds has been inflicted by human beings.
0:35:43 > 0:35:47The huia, which once lived in New Zealand's woodlands,
0:35:47 > 0:35:54was hunted precisely because it was rare and was finally totally gone in 1907.
0:35:54 > 0:35:59The great auk, a giant, flightless relation of the razorbill,
0:35:59 > 0:36:04was hunted and exterminated by the middle of the 19th century.
0:36:04 > 0:36:09The dodo, a pigeon that, safe in its island sanctuary of Mauritius,
0:36:09 > 0:36:12also evolved into a flightless giant,
0:36:12 > 0:36:19was easy prey for sailors. They exterminated it by the middle of the 17th century,
0:36:19 > 0:36:23less than 200 years after men first set foot on their island.
0:36:23 > 0:36:30It's not only on islands that birds are vulnerable to changes brought by humanity.
0:36:30 > 0:36:35150 years ago, prairies like this in the US
0:36:35 > 0:36:40were home to flocks of birds two to three thousand MILLION strong.
0:36:40 > 0:36:45They were so big they darkened the skies and took three days to pass.
0:36:45 > 0:36:51They were probably the most numerous bird that has ever existed on earth -
0:36:51 > 0:36:54passenger pigeons.
0:36:54 > 0:37:01Their numbers were so astronomic that no-one considered them as anything but pests,
0:37:01 > 0:37:06nor could imagine that they would ever be in danger of extinction.
0:37:06 > 0:37:12But a combination of hunting and changes to the landscape brought by farming destroyed them.
0:37:12 > 0:37:17The last wild passenger pigeon was sighted in 1889
0:37:17 > 0:37:22and the last survivor of all, a lonely female called Martha,
0:37:22 > 0:37:25died in Cincinnati Zoo in 1914.
0:37:25 > 0:37:29Birds are still being slaughtered in huge numbers today,
0:37:29 > 0:37:34particularly when there are economic reasons for doing so.
0:37:36 > 0:37:41Dickcissels in Venezuela also swarm in flocks millions strong.
0:37:41 > 0:37:49The whole world's population comes here in winter, sometimes roosting in only three or four sites.
0:37:49 > 0:37:56Should anything happen to those sites, the dickcissels could go the same way as the passenger pigeon,
0:37:56 > 0:37:59and they are a very serious pest.
0:37:59 > 0:38:04Farmers know how to deal with INSECT pests.
0:38:10 > 0:38:13They spray them with poisons.
0:38:18 > 0:38:23So the same technique is sometimes used against dickcissels,
0:38:23 > 0:38:27in spite of the fact that it's against the law.
0:38:28 > 0:38:32The birds, recorded here by amateur video,
0:38:32 > 0:38:35take several days to die.
0:38:37 > 0:38:43Yet humanity, so often in the past the mindless and merciless exterminator of birds,
0:38:43 > 0:38:46can sometimes become their guardians.
0:39:02 > 0:39:09In West Africa, in Cameroon, villagers celebrate the forest beside which they live
0:39:09 > 0:39:13and in particular one of its birds.
0:39:17 > 0:39:20Bannerman's turaco.
0:39:20 > 0:39:28Many of the creatures of the forest, such as the elephant, that also feature in this celebration,
0:39:28 > 0:39:31have long since disappeared.
0:39:31 > 0:39:33The turaco, however, still survives,
0:39:33 > 0:39:38though in this forest there are only about 4,000 pairs
0:39:38 > 0:39:41and it lives nowhere else.
0:39:47 > 0:39:55For decades, the forest has been felled to make way for fields in which the people can grow their food.
0:39:55 > 0:39:59It's now only half the size it was 30 years ago.
0:39:59 > 0:40:04Yet the people also know that they depend on the forest -
0:40:04 > 0:40:09for water and firewood, for medicine and for meat.
0:40:09 > 0:40:12So now a balance has been struck.
0:40:12 > 0:40:19The traditional beliefs of the people have been harnessed to come to the forest's defence.
0:40:19 > 0:40:26The masked figure of Mabu, their spirit guardian, accompanied by the village elders,
0:40:26 > 0:40:30regularly patrols the margins of the forest.
0:40:30 > 0:40:36Stakes are planted to mark the point beyond which no tree may be felled.
0:40:36 > 0:40:42The turaco has become a symbol of the villagers' regard for their environment.
0:40:42 > 0:40:47Mabu is in league with international bird conservation bodies
0:40:47 > 0:40:53who are also concerned about the survival of Bannerman's turaco.
0:40:58 > 0:41:01MAN PURRS AND WHOOPS
0:41:01 > 0:41:09In North America, there are other masquerades to protect a bird that is even rarer than the turaco.
0:41:09 > 0:41:17A whooping crane chick learns to feed, encouraged by the gestures and calls of human foster parents.
0:41:20 > 0:41:24In 1945, only 16 whooping cranes existed.
0:41:24 > 0:41:26Today, there are 300,
0:41:26 > 0:41:32thanks to captive breeding and the patient rearing of chicks by hand.
0:41:32 > 0:41:40And this is surely one of the most extraordinary hand-rearing devices yet invented -
0:41:40 > 0:41:43a whooping crane adult glove puppet,
0:41:43 > 0:41:48with a trigger inside so that I can operate the beak.
0:41:48 > 0:41:55I'm speaking quietly because behind these doors are whooping crane chicks
0:41:55 > 0:42:00and it's important they don't get used to the sound of human voices
0:42:00 > 0:42:03at this early stage in their lives.
0:42:03 > 0:42:09It's even more important that they don't SEE humans, which is why they're fed with this.
0:42:16 > 0:42:21Here at the International Crane Foundation in Wisconsin,
0:42:21 > 0:42:28they believe that were the chicks fed by humans directly and visibly, they'd risk becoming humanised,
0:42:28 > 0:42:34so that as adults, they wouldn't be able to breed with their own kind.
0:42:45 > 0:42:50As they grow, the whoopers lose all their brown plumage
0:42:50 > 0:42:52and replace it with white feathers.
0:42:54 > 0:42:58They must now learn how to use them in flight.
0:43:09 > 0:43:15And once again, they have to be shown the sort of thing they must do.
0:43:24 > 0:43:27Away to the west, in Idaho,
0:43:27 > 0:43:34a farmer with a passion for cranes, Kent Clegg, has also been rearing a small group of chicks.
0:43:34 > 0:43:39He has a mechanised way of persuading his little flock to fly.
0:43:39 > 0:43:43He has reared them in a quite different way -
0:43:43 > 0:43:49initially in small groups, which he believes will avoid humanisation.
0:43:49 > 0:43:52He then taught them to follow him.
0:43:52 > 0:44:00He's put them together with the young of a commoner, smaller species, sandhill cranes, the all-brown ones.
0:44:04 > 0:44:09So the little mixed flock has become confident in the air.
0:45:25 > 0:45:30There's one further problem - whooping cranes are migratory.
0:45:30 > 0:45:38In the past, some used to overwinter in the US, but many, in the autumn, would fly south to New Mexico.
0:45:38 > 0:45:42These birds might try to do the same thing,
0:45:42 > 0:45:49but how would they know which way to go without their parents to guide them?
0:45:49 > 0:45:52Well, that problem is being tackled too.
0:46:05 > 0:46:11Kent Clegg is planning to lead them there himself in his microlight.
0:46:53 > 0:46:59Birds were flying from continent to continent long before we were.
0:46:59 > 0:47:04They reached the coldest place on earth long before we did.
0:47:04 > 0:47:07They can survive in the deserts.
0:47:07 > 0:47:11Some can remain on the wing for years at a time.
0:47:11 > 0:47:17Now we have taken over the earth and the sea and the sky,
0:47:17 > 0:47:20but with skill, care and knowledge
0:47:20 > 0:47:24we can ensure that there is still a place on earth for birds
0:47:24 > 0:47:27in all their beauty and variety...
0:47:27 > 0:47:31if we want to... and surely we should.
0:48:47 > 0:48:52Subtitles by Neil Gemmill BBC Scotland - 1998