0:00:02 > 0:00:07*
0:01:05 > 0:01:10Birds are the most accomplished aeronauts the world has ever seen.
0:01:10 > 0:01:14They fly high...and low, at great speed...
0:01:14 > 0:01:17and very slowly...
0:01:17 > 0:01:22and always with extraordinary precision and control.
0:02:16 > 0:02:20But birds are not the only creatures in the air.
0:02:20 > 0:02:26There are also small furry mammals - bats, like these in Texas.
0:02:26 > 0:02:29They are so competent in the air,
0:02:29 > 0:02:34that they have just made a journey from Mexico, a thousand miles away,
0:02:34 > 0:02:37to rear their young in this cave,
0:02:37 > 0:02:40which is suitable for them as a nursery.
0:02:40 > 0:02:45Now, they are out to catch their evening meal of insects.
0:02:45 > 0:02:52But they had better be careful because above them, there lurks a creature that can outfly them.
0:02:54 > 0:02:59It is, of course, a bird - a red-tailed hawk.
0:02:59 > 0:03:04Bats, with their fluttering zig-zag flight, are not easy targets,
0:03:04 > 0:03:09and a hawk needs all its aerobatic skills and powers of concentration
0:03:09 > 0:03:13to snatch one out of the confusing multitude.
0:03:29 > 0:03:34That is one bat that will not return to the roost tonight.
0:03:37 > 0:03:40The red-tail lives beside the cave
0:03:40 > 0:03:44and is well practised in bat-catching.
0:03:46 > 0:03:52This prairie falcon, however, is a visitor, but it's learning fast.
0:04:03 > 0:04:08Unlike the hawk, it chooses to eat its meals on the wing.
0:04:14 > 0:04:17Bats are latecomers to the skies.
0:04:17 > 0:04:21They've only been flying for a mere 60 million years.
0:04:21 > 0:04:26The air was first colonised 200 million years earlier -
0:04:26 > 0:04:30by the insects - but now they can't escape the birds either.
0:05:10 > 0:05:14Some insects, of course, have powerful weapons
0:05:14 > 0:05:17 with which to defend themselves.
0:05:17 > 0:05:22But a bee-eater certainly knows how to deal with a bee.
0:05:31 > 0:05:36A rub against the perch usually discharges the sting.
0:05:36 > 0:05:39And if that doesn't,
0:05:39 > 0:05:45then a sharp nip will squirt the venom harmlessly into the air.
0:06:05 > 0:06:10Dragonflies first flew around 350 million years ago;
0:06:10 > 0:06:16and insects had the skies to themselves for 150 million years thereafter.
0:06:16 > 0:06:20And then a different kind of animal joined them in the air.
0:06:22 > 0:06:25As the dinosaurs dominated the land,
0:06:25 > 0:06:29so the pterosaurs now ruled the skies.
0:06:33 > 0:06:40Pterosaurs had wings of skin stretched between one enormously elongated finger and their flanks.
0:06:41 > 0:06:46They flew over the sea as well as the land.
0:06:49 > 0:06:54It seems likely that some roosted on cliffs
0:06:54 > 0:06:59and launched themselves into the air as gannets do today.
0:07:03 > 0:07:09They probably snatched fish from the surface of the sea,
0:07:09 > 0:07:12and some certainly fell into it.
0:07:11 > 0:07:12AARK!
0:07:20 > 0:07:25Their bodies were buried by mud, the mud turned to limestone
0:07:25 > 0:07:31and eventually became exposed in quarries like this one in Germany.
0:07:35 > 0:07:39Today, separating the layers of sediment
0:07:39 > 0:07:43is like searching through the pages of a visitors' book
0:07:43 > 0:07:47that hasn't been opened for 150 million years.
0:07:47 > 0:07:52Of course, nearly all the pages are absolutely blank.
0:07:52 > 0:07:55Visitors, after all, were very few.
0:07:55 > 0:08:01But now and again you come across a signature that is unmistakable.
0:08:02 > 0:08:05A fish the size of a sardine.
0:08:05 > 0:08:10A shrimp - even its antennae perfectly preserved.
0:08:10 > 0:08:15One of the pioneering dragonflies - nearly six inches across.
0:08:15 > 0:08:20And a pterosaur with skinny wings and teeth in its jaws.
0:08:20 > 0:08:27With so many superb fossils, people thought that they had a complete list of the visitors to the lagoon.
0:08:27 > 0:08:32And then, in the middle of the last century, a signature was discovered
0:08:32 > 0:08:37that was wholly unexpected and totally amazing. This is it.
0:08:37 > 0:08:39It's a feather.
0:08:39 > 0:08:46Its barbs are narrower on one side of the quill than the other, as they are on a modern bird's wing.
0:08:46 > 0:08:51This asymmetry is a sure sign that such feathers were used for flight.
0:08:51 > 0:08:56But what animal at the time of the dinosaurs could have such a wing?
0:08:56 > 0:09:00The answer was found the very next year in the same quarry.
0:09:00 > 0:09:06A fossil with its feathers still attached to its body.
0:09:06 > 0:09:09This is archaeopteryx.
0:09:11 > 0:09:17It had three toes armed with claws and long, strong legs.
0:09:17 > 0:09:21Clearly, it walked and perched like a bird.
0:09:21 > 0:09:26But its head was very reptilian, with bony jaw bones.
0:09:26 > 0:09:29And in those jaws - teeth.
0:09:32 > 0:09:38Its spine was extended into a bony tail - again like that of a reptile.
0:09:38 > 0:09:40But on either side of the tail bones,
0:09:40 > 0:09:46it had those characteristic possessions of birds - feathers.
0:09:46 > 0:09:51Feathers are made of keratin, as are the scales on the legs of many birds
0:09:51 > 0:09:56and all over the bodies of reptiles. A scaly coat must be very hot,
0:09:56 > 0:10:03so reptiles like this skink have to seek shade during the hottest part of the day.
0:10:03 > 0:10:10But if the scales became fibrous, they could be fluffed up to let in cooling air during the day,
0:10:10 > 0:10:15and closed down to trap insulating air for warmth at night.
0:10:15 > 0:10:21So it is not hard to believe that scales eventually became feathers.
0:10:21 > 0:10:27But why did they become so long that they enabled an animal to fly?
0:10:27 > 0:10:30This Australian lizard has one answer.
0:10:30 > 0:10:34When it is threatened by its enemies,
0:10:34 > 0:10:40it responds by spreading the great frill it has around its neck.
0:10:40 > 0:10:45But if that doesn't scare them off, it runs away...on its hind legs.
0:10:45 > 0:10:53If such a reptile had developed feathery scales on its forelegs and then spread them out,
0:10:53 > 0:10:59then it might easily lift into the air and escape a land-bound predator.
0:11:02 > 0:11:05Here's another possibility.
0:11:05 > 0:11:10Maybe that early reptile did not live on the ground, but in the trees,
0:11:10 > 0:11:15as today, the little flying lizard of Borneo does.
0:11:15 > 0:11:18It now glides from tree to tree.
0:11:18 > 0:11:21It has developed wings
0:11:21 > 0:11:25that are flaps of skin supported by elongated ribs.
0:11:31 > 0:11:35If that early enterprising reptile with feathery scales
0:11:35 > 0:11:38did have extra long ones on its arms,
0:11:38 > 0:11:42then they too would have enabled it to glide from tree to tree.
0:11:42 > 0:11:50Maybe its arm muscles were even strong enough to allow it to make a few flaps to help it on its way.
0:11:50 > 0:11:54Archaeopteryx was certainly well-equipped for climbing,
0:11:54 > 0:12:00for its wings still carried three fingers, each with a hooked claw.
0:12:00 > 0:12:05And there are birds today with very similar ones that give a clear hint
0:12:05 > 0:12:08as to how it might have used them.
0:12:08 > 0:12:14These young hoatzin in South America are still guarded by their parents.
0:12:14 > 0:12:18A hoatzin chick has an adventurous disposition
0:12:18 > 0:12:22and starts clambering about when only a few days old.
0:12:30 > 0:12:35The hooks on its front limbs are useful in keeping it secure
0:12:35 > 0:12:39until they become feathered and reliable wings.
0:12:40 > 0:12:45One can imagine that archaeopteryx used them in much the same way.
0:12:47 > 0:12:50Sometimes, however, there's a disaster.
0:12:53 > 0:12:58There are dangerous reptiles in the swamp - snakes and cayman.
0:13:00 > 0:13:06But those claws on the wings are, once again, invaluable.
0:13:10 > 0:13:15Mother returns. She has been feeding on leaves and will have a full crop.
0:13:15 > 0:13:19Maybe there will be some for the chick.
0:13:29 > 0:13:36The hoatzin, like all modern birds, doesn't have bony jaws with teeth like archaeopteryx,
0:13:36 > 0:13:42but a lightweight beak. When did that important change take place?
0:13:43 > 0:13:48This fossilised bird HAS a beak. It was found in China recently.
0:13:48 > 0:13:54It's just younger than archaeopteryx, so the change took place quickly.
0:13:54 > 0:13:59The beak prevented the bird from being nose-heavy
0:13:59 > 0:14:03and significantly reduced its overall weight.
0:14:03 > 0:14:08By 50 million years ago, the dynasty of birds was firmly established.
0:14:08 > 0:14:13At that time, a great lake lay here in central Germany.
0:14:13 > 0:14:19It dried out long ago and the layers of mud have turned into shales.
0:14:19 > 0:14:24Excavations like the one that's going on here,
0:14:24 > 0:14:29have revealed just how varied the birds had become.
0:14:29 > 0:14:35This one's been set in yellow resin to make its details quite clear.
0:14:35 > 0:14:39It had a horny beak, a fully-feathered wing,
0:14:39 > 0:14:43a long feathered tail with no bony support,
0:14:43 > 0:14:48and long legs. It probably looked like a...rail.
0:14:49 > 0:14:57Other fossils from these shales show that several families of modern birds were already established.
0:14:57 > 0:15:01This was a water bird - possibly an ancestor of today's jacana.
0:15:01 > 0:15:06It would have found insects among the leaves on the lake.
0:15:06 > 0:15:12There were birds with chisel-like bills. Perhaps they were woodpeckers
0:15:12 > 0:15:19that even in this early period had started excavating insects from the trees in the surrounding forest.
0:15:19 > 0:15:25Another resident of those woods had a stubbier, more all-purpose beak,
0:15:25 > 0:15:27rather like finches do today.
0:15:30 > 0:15:34There were tall birds with long, powerful legs
0:15:34 > 0:15:38that probably hunted for small reptiles on the ground,
0:15:38 > 0:15:41as the South American seriema does.
0:15:47 > 0:15:53And there was a gigantic vulture with a wingspan of over 20 feet -
0:15:53 > 0:15:56bigger than that of the Andean condor
0:15:56 > 0:16:02and probably the biggest flying bird that has ever existed.
0:16:08 > 0:16:13There were even birds which, judging from their skeletons,
0:16:13 > 0:16:18were as agile as their probable descendants, the frigate birds.
0:16:18 > 0:16:21So by 50 million years ago,
0:16:21 > 0:16:26several families of modern birds were well established.
0:16:26 > 0:16:33The rule of the reptiles was now over. Not only had pterosaurs disappeared from the skies,
0:16:33 > 0:16:35dinosaurs had gone from the ground.
0:16:35 > 0:16:43So the dominance of the land was up for grabs. There were two contenders: the mammals and the birds.
0:16:43 > 0:16:50The biggest mammal found from this lake in Germany was a primitive horse, no bigger than a spaniel.
0:16:50 > 0:16:53The biggest bird was very different.
0:16:53 > 0:16:56That was the lower part of its beak,
0:16:56 > 0:16:59 and this was the upper.
0:17:02 > 0:17:09If its skeleton still lay here, you would have to dig a huge pit to extract it.
0:17:09 > 0:17:12This bird was immense.
0:17:17 > 0:17:21It has been named - with good reason - the terror bird.
0:17:23 > 0:17:25Its wings were tiny,
0:17:25 > 0:17:28but it had long and powerful legs.
0:17:43 > 0:17:47Flightless birds of a comparable size still exist
0:17:47 > 0:17:52and can give us some idea of what it looked like.
0:17:52 > 0:17:57This, the ostrich, is the biggest and heaviest bird alive today.
0:17:57 > 0:18:04It is probably not closely related to those monstrous feathered hunters of prehistory,
0:18:04 > 0:18:09but together with the Australian emu and the rhea of South America,
0:18:09 > 0:18:17it belongs to a very ancient family of birds that abandoned flight a very long time ago.
0:18:18 > 0:18:21It relies for its defence on speed,
0:18:21 > 0:18:25and to increase its efficiency as a runner,
0:18:25 > 0:18:27its toes have been reduced to two.
0:18:27 > 0:18:32If pursued, it can sprint at over 40 miles an hour.
0:18:41 > 0:18:43But although it is now flightless,
0:18:43 > 0:18:49it still has many of the physical characters evolved by its ancestors
0:18:49 > 0:18:51that enabled THEM to fly.
0:18:51 > 0:18:56It still has feathers. They are still placed on its wings
0:18:56 > 0:19:01in much the same position as those on the wings of a flying bird.
0:19:01 > 0:19:05But they are now useless for flight.
0:19:05 > 0:19:11Their filaments have no hooks, so cannot be zipped together into an unbroken blade.
0:19:11 > 0:19:14Instead, they are loose and fluffy.
0:19:14 > 0:19:21Their only function now is as insulation - to keep out the cold at night and the heat during the day.
0:19:23 > 0:19:26Ostriches have become grazers -
0:19:26 > 0:19:30the bird equivalent of antelope or horses.
0:19:38 > 0:19:43But unlike them, they not only pick up leaves,
0:19:43 > 0:19:49they swallow all kinds of other things too - and for a good reason.
0:19:49 > 0:19:56Just as they inherited feathers from their flying ancestors, they also inherited a light, horny beak
0:19:56 > 0:20:00instead of a heavy jaw laden with teeth.
0:20:00 > 0:20:05And without teeth, they need another way to grind up their food.
0:20:05 > 0:20:09A pebble can help them do just that.
0:20:14 > 0:20:20It goes into a muscular compartment of the stomach - the gizzard,
0:20:20 > 0:20:27a kind of mill where bits of vegetation are churned around and ground into a digestible pulp.
0:20:30 > 0:20:34But while some birds were abandoning flight,
0:20:34 > 0:20:38some mammals were becoming formidable hunters.
0:20:42 > 0:20:46Ostriches, with their superb eyesight and tall necks,
0:20:46 > 0:20:50can keep a sharp lookout for danger.
0:20:54 > 0:21:00The cheetah has to calculate whether it's worthwhile chasing something...
0:21:00 > 0:21:04and an ostrich, usually, is not. It is so fast,
0:21:04 > 0:21:10and it has little meat on it compared with a similar sized mammal.
0:21:10 > 0:21:16But birds that can't run are a tempting target for hunters.
0:21:24 > 0:21:28If they couldn't fly, they wouldn't last long.
0:22:16 > 0:22:21Flight has certainly enabled birds to colonise the entire globe.
0:22:21 > 0:22:28But the compulsion that drove them into the air in the first place,
0:22:28 > 0:22:33and has kept most of them there ever since, was probably safety.
0:22:33 > 0:22:36 Even so, the cost of flying is high.
0:22:36 > 0:22:42Flapping wings takes a lot of effort and if there is no need to do so, birds save energy.
0:22:42 > 0:22:47Those that live here on the isolated Galapagos Islands,
0:22:47 > 0:22:54have no natural enemies from which to escape, so some birds don't bother to fly.
0:22:54 > 0:22:58Have a look at these cormorants, for example.
0:22:58 > 0:23:05At first sight, they look like any other cormorant to be found sitting on cliffs round the world.
0:23:05 > 0:23:10But these wings are stunted and tattered.
0:23:10 > 0:23:12CROAKS
0:23:14 > 0:23:16This bird could never fly.
0:23:16 > 0:23:21Its feathers serve only to keep it warm in the water.
0:23:21 > 0:23:25It's for that reason alone that it keeps them well-oiled.
0:23:30 > 0:23:35It is scarcely any better at walking than it is at flying.
0:23:55 > 0:24:00Once in the water, however, it's a very efficient mover indeed.
0:24:16 > 0:24:22The position of its legs right at the back of its body that made it so clumsy on land
0:24:22 > 0:24:25is ideal for speeding through water
0:24:25 > 0:24:29and helps it to catch all the fish it needs.
0:24:33 > 0:24:38For the Galapagos cormorant, flight has become an irrelevance.
0:24:40 > 0:24:44Other island birds have reacted in a similar way.
0:24:44 > 0:24:51This is New Caledonia in the western Pacific - and this is its special bird, the kagu.
0:24:51 > 0:24:59Its ancestors must have arrived here by air, but since New Caledonia had no ground predators until recently,
0:24:59 > 0:25:04they gave up flying and today the kagu is virtually flightless.
0:25:05 > 0:25:11It finds all its food on the ground in the leaf litter.
0:25:11 > 0:25:19It's been here so long, it's not clear who its ancestors were, but they were probably herons.
0:25:35 > 0:25:39Rails are a very widespread family of birds.
0:25:39 > 0:25:44Wherever there is a big swamp, you are likely to find one.
0:25:44 > 0:25:49On the continents, they tend to lurk shyly in the undergrowth,
0:25:49 > 0:25:57but some have also managed to reach a great number of islands, and there they seem to have no fear at all.
0:25:57 > 0:26:02This one - it's a weka - has also become flightless
0:26:02 > 0:26:06because of its isolation on an island.
0:26:06 > 0:26:10But its island...is immense.
0:26:10 > 0:26:18It's a thousand miles long if you discount a narrow arm of sea crossing it in the middle,
0:26:18 > 0:26:23and it contains mountains over 12,000 feet high. It's New Zealand.
0:26:23 > 0:26:28The first land-living mammals to get here were human beings
0:26:28 > 0:26:32and they didn't arrive until 1,500 years ago.
0:26:32 > 0:26:36So here you can see what the world would have been like
0:26:36 > 0:26:43if the birds had won that battle with the early mammals and now ruled the earth...for here they once did.
0:26:47 > 0:26:52Many of New Zealand's birds flew here from Australia,
0:26:52 > 0:26:551,500 miles away across the sea.
0:26:55 > 0:27:02They started to do so millions of years ago and they are still doing so today.
0:27:07 > 0:27:10So if you know Australian birds,
0:27:10 > 0:27:17you will recognise quite a lot, particularly those that are relatively recent arrivals.
0:27:19 > 0:27:24The New Zealand pigeon is not very much different from Australian ones.
0:27:24 > 0:27:30The saddleback, however, must have been living here for much longer,
0:27:30 > 0:27:36for it's changed so much that no-one is sure what family it belongs to.
0:27:37 > 0:27:40The tui has similarly mysterious origins.
0:27:40 > 0:27:45No other bird has a costume like its lacy cape
0:27:45 > 0:27:48and that little white throat bobble.
0:27:55 > 0:28:00The kaka is clearly a parrot. There are lots of parrots in Australia
0:28:00 > 0:28:05so it's not surprising that some have found their way here.
0:28:09 > 0:28:15Most of these birds have still not learned that mammals are dangerous.
0:28:15 > 0:28:18This saddleback is a fully wild bird
0:28:18 > 0:28:24and certainly hasn't seen me before. But look how trusting it is.
0:28:32 > 0:28:38This is a New Zealand robin. It's no relation to the European robin
0:28:38 > 0:28:41and, if anything, it's even braver.
0:28:49 > 0:28:55New Zealand is full of food, and as the birds once had it all to themselves,
0:28:55 > 0:29:01some adopted diets and lifestyles that elsewhere were claimed by mammals.
0:29:01 > 0:29:05The kokako eats much the same thing as squirrels -
0:29:05 > 0:29:08fruit and leaves and insects.
0:29:12 > 0:29:16European squirrels run along the branches;
0:29:16 > 0:29:21Asian squirrels, using a skinny parachute,
0:29:21 > 0:29:24 are able to glide as well.
0:29:24 > 0:29:29And that is very much how the kokako gets around in the trees.
0:29:43 > 0:29:46Having glided down the branches,
0:29:46 > 0:29:49it runs back up them
0:29:49 > 0:29:51and jumps from one to the other.
0:30:13 > 0:30:16So if the kokako, up in the trees,
0:30:16 > 0:30:20feeds in the same way as a squirrel might do,
0:30:20 > 0:30:24what lives and feeds like a mammal on the ground?
0:30:24 > 0:30:29The leaf litter in these forests is full of food.
0:30:29 > 0:30:34There are earthworms and insects and beetle larvae.
0:30:35 > 0:30:41In any other land, there would be some small mammal burrowing around, seeking that food.
0:30:41 > 0:30:46But not here in New Zealand. Here there's something different.
0:30:47 > 0:30:50You will only see it after dark.
0:30:59 > 0:31:02It is, of course, a bird,
0:31:02 > 0:31:06but what an extraordinary one. The kiwi.
0:31:08 > 0:31:14It's territorial and calls stridently to proclaim its ownership.
0:31:14 > 0:31:17RATTLING CALL
0:31:26 > 0:31:29It finds its prey by smell.
0:31:29 > 0:31:33Uniquely, its nostrils are on the tip of its beak.
0:31:36 > 0:31:39It's found a worm.
0:31:40 > 0:31:45But once it drops it, its eyesight is so poor that it can't see it
0:31:45 > 0:31:49and it has to smell for it - with its beak.
0:31:53 > 0:31:59Its tiny vestigial wings are invisible, buried in its plumage,
0:31:59 > 0:32:02and it has lost all sign of a tail.
0:32:05 > 0:32:09If the kiwis live in forest close by the sea,
0:32:09 > 0:32:15in the evening, they may come down onto the beach to look for these -
0:32:15 > 0:32:20sandhoppers. They love 'em. And that will give us a chance,
0:32:20 > 0:32:24a rare chance, to see them out in the open.
0:32:27 > 0:32:33To do so properly, we have to use our special starlight camera.
0:32:46 > 0:32:49The kiwi is hunting along the strandline
0:32:49 > 0:32:53for hoppers feeding on the decaying seaweed.
0:32:56 > 0:32:59Its sense of smell is so acute,
0:32:59 > 0:33:04it can pick out the largest, juiciest hoppers deep in the sand
0:33:04 > 0:33:06without even seeing them.
0:33:06 > 0:33:11Our starlight camera can see much better than I can.
0:33:11 > 0:33:16I need a torch to see this extraordinary creature properly...
0:33:16 > 0:33:19but it doesn't seem to mind.
0:33:29 > 0:33:32Its feathers are just filaments,
0:33:32 > 0:33:37so that it almost looks as if it is covered with coarse fur.
0:33:43 > 0:33:47Probing sand with your nostrils is all very well,
0:33:47 > 0:33:52but it does clog them up, so you need to blow them clear now and then.
0:34:05 > 0:34:10It's nocturnal and furry, it finds its way around by smell,
0:34:10 > 0:34:14it lives in holes and digs for worms and grubs.
0:34:14 > 0:34:17It's a bird equivalent of a badger.
0:34:24 > 0:34:30But there's plenty of other food to be found in the New Zealand bush.
0:34:30 > 0:34:34Here on the forest floor, there are lots of leaves.
0:34:34 > 0:34:40They may be a bit twiggy and coarse but they are food. What could have browsed on these?
0:34:42 > 0:34:44Well, not far from here,
0:34:44 > 0:34:47bones like this have been dug up.
0:34:47 > 0:34:54It's obviously a leg bone, and at first sight you might think it was the bone of a mammal, perhaps a cow.
0:34:54 > 0:34:57But when you look closely,
0:34:57 > 0:35:02you can see a honeycomb structure - a lightweight bone. It's a bird bone,
0:35:02 > 0:35:06but the bone of a very big bird indeed,
0:35:06 > 0:35:10as we know from the rest of its skeleton.
0:35:15 > 0:35:18It had just three toes.
0:35:20 > 0:35:25Its pelvis and its spine lead up to an extraordinarily long neck.
0:35:29 > 0:35:33This bird stood over six feet - two metres tall.
0:35:39 > 0:35:45The first human settlers here saw them alive and called them moas.
0:35:45 > 0:35:49Among them were the tallest birds that ever existed,
0:35:49 > 0:35:53that weighed over 200 kilos - 400lbs.
0:35:53 > 0:35:59There were about a dozen different species of varying size and weight.
0:36:11 > 0:36:14Up on the high moorlands,
0:36:14 > 0:36:19there were smaller species with thicker feathers to keep them warm.
0:36:19 > 0:36:25The absence of mammals didn't mean that the moas had no enemies.
0:36:25 > 0:36:29They were hunted by, of course, another bird.
0:36:37 > 0:36:42An immense eagle that could manoeuvre through the patchy forest.
0:36:42 > 0:36:47The only prey abundant enough to feed such a giant were other birds,
0:36:47 > 0:36:52and it could probably tackle even the biggest moa.
0:36:52 > 0:36:57Its talons were long enough to stab through the flesh into its pelvis,
0:36:57 > 0:37:00as some of the bones show.
0:37:00 > 0:37:05Nevertheless, the moas survived for a million years or more
0:37:05 > 0:37:08and spread all over New Zealand.
0:37:08 > 0:37:15But eventually mammals DID reach these remote islands. Apart from bats which flew here,
0:37:15 > 0:37:20the first to arrive were those most dangerous of all - human beings.
0:37:20 > 0:37:25They hunted the moas for meat and soon hunted them to extinction.
0:37:25 > 0:37:33But a different kind of flightless bird does still survive, up in these high mountains.
0:37:33 > 0:37:40Like so many of New Zealand's native birds that had abandoned flight and nested on the ground,
0:37:40 > 0:37:45it had no defence against the alien mammals that Europeans brought
0:37:45 > 0:37:48and that soon escaped and ran wild.
0:37:48 > 0:37:51Rats ate their eggs and killed the chicks,
0:37:51 > 0:37:55cats and stoats massacred the adults.
0:37:57 > 0:38:02There was a giant flightless coot that was originally very common.
0:38:02 > 0:38:07But it got scarcer and scarcer and by the middle of the 19th century,
0:38:07 > 0:38:10it was thought to be extinct.
0:38:10 > 0:38:15And then, just 50 years ago, someone in these remote valleys
0:38:15 > 0:38:18 found something like this.
0:38:19 > 0:38:22This is the dropping of a takahe,
0:38:22 > 0:38:25and here...
0:38:25 > 0:38:30the severed stems of tussock grass on which it's been feeding.
0:38:30 > 0:38:33It's still here.
0:38:35 > 0:38:39(And here is her nest.)
0:38:48 > 0:38:50She's sitting tight,
0:38:50 > 0:38:55hiding her brilliant red bill so she is not conspicuous.
0:39:04 > 0:39:09Indeed, when only her lovely moss-green back is visible,
0:39:09 > 0:39:16she is well camouflaged from her only native enemy - a bird of prey circling overhead.
0:39:18 > 0:39:23Only about 40 pairs of takahe survive today in the wild,
0:39:23 > 0:39:27so the eggs she is sitting on are very precious.
0:39:27 > 0:39:32This high country was probably not the takahe's original home.
0:39:32 > 0:39:39Most in the last century lived lower down where they fed on lush vegetation in the warm swamps.
0:39:39 > 0:39:44But most of those were drained and turned into farmland.
0:39:44 > 0:39:50So now these high empty valleys, scraped down to the rock by glaciers,
0:39:50 > 0:39:52are the takahe's last refuge.
0:39:52 > 0:39:56There is little to eat up here except tussock grass.
0:40:14 > 0:40:19Extracting something nutritious from tussock is not easy.
0:40:19 > 0:40:25The takahe's technique is to pull up a whole stem and then nibble the bottom inch.
0:40:25 > 0:40:33That's where most of the minerals and sugars are and it's the only bit tender enough to be easily cut.
0:40:44 > 0:40:49At first the chick doesn't know how to do this and has to be fed.
0:40:49 > 0:40:53It will stay with its parent for a whole year.
0:40:53 > 0:40:58Only then will it be skilled enough to feed entirely by itself.
0:41:02 > 0:41:08Now it's summer, but when winter comes, life will be even tougher.
0:41:08 > 0:41:13Then the pools freeze over and the tussock has no fresh shoots
0:41:13 > 0:41:20even if they could be reached under the snow. Then the takahe has to dig for tubers in the freezing earth.
0:41:20 > 0:41:27So the birds' continued survival up here in these barren moorlands is by no means assured.
0:41:29 > 0:41:35One other flightless bird found refuge from mammals in these high mountains,
0:41:35 > 0:41:42and in many ways, it was the most extraordinary of all. It was a giant parrot, the kakapo.
0:41:42 > 0:41:46It lived in much the same way as rabbits do.
0:41:46 > 0:41:51It made tracks through its territory, generation after generation,
0:41:51 > 0:41:56trudging along here and feeding by plucking these grasses
0:41:56 > 0:41:59and eating the succulent base.
0:42:00 > 0:42:03This path runs under this bush
0:42:03 > 0:42:08and continues upwards along the highest edge of this narrow ridge.
0:42:17 > 0:42:22The track leads to this shallow bowl,
0:42:22 > 0:42:27and there are others like it spaced out along the track.
0:42:27 > 0:42:33They were excavated by the male kakapo whose territory this was.
0:42:33 > 0:42:38In the night he would come here and crouching low,
0:42:38 > 0:42:43would make a deep booming call which echoed out across these valleys,
0:42:43 > 0:42:46summoning the females to come to him.
0:42:48 > 0:42:53But there were no females seen after the 1970s up here.
0:42:53 > 0:42:59One lone male continued trudging up here and calling...but in vain.
0:42:59 > 0:43:04And in 1985, his call was heard no more.
0:43:09 > 0:43:14When hope was almost gone, a new population of kakapos was discovered
0:43:14 > 0:43:18on the southernmost island - Stewart Island.
0:43:18 > 0:43:22They too were being harried by cats and stoats,
0:43:22 > 0:43:27so the survivors were caught and taken to three small cat-free islets.
0:43:27 > 0:43:29There were only 61 of them.
0:43:29 > 0:43:34The kakapo's survival was on a knife edge.
0:43:44 > 0:43:48A male, after slumbering all day in his burrow,
0:43:48 > 0:43:51emerges for his evening meal.
0:43:53 > 0:43:57His hearing is acute - he listens for danger.
0:44:18 > 0:44:21He's following his regular track
0:44:21 > 0:44:26that will lead him to the highest slopes of his mountain.
0:44:31 > 0:44:36A female has clambered up into the top of the bushes,
0:44:36 > 0:44:39looking for fresh shoots and fruit.
0:44:41 > 0:44:47Her dappled plumage camouflages her against attacks from falcons,
0:44:47 > 0:44:54but even so, she won't dare to venture into the topmost branches until it's dark.
0:44:58 > 0:45:04Nightfall. Now we need our starlight camera to see what's happening.
0:45:07 > 0:45:09By midnight,
0:45:09 > 0:45:14the male has plodded his way right to the summit of his mountain.
0:45:17 > 0:45:20He has reached one of his bowls
0:45:20 > 0:45:25from which his call could echo out over the valley below.
0:45:25 > 0:45:28He begins to tidy it up.
0:45:36 > 0:45:41The female has found what she wants in the branches.
0:45:41 > 0:45:46She'll need all the nourishment she can find if she is to produce an egg.
0:45:46 > 0:45:54Even at the best of times, she will not accumulate enough bodily reserves to lay every year.
0:45:58 > 0:46:02The male begins to inflate air sacs on his chest
0:46:02 > 0:46:07that will act as resonators and so amplify his calls,
0:46:07 > 0:46:11sending them booming out across the valley.
0:46:11 > 0:46:14RHYTHMIC HISSING
0:46:27 > 0:46:30DEEP HONKS
0:46:36 > 0:46:39DISTANT HONKS
0:46:49 > 0:46:52DEEP HONKING
0:46:55 > 0:47:00There are probably only 12 fertile female kakapos left alive.
0:47:00 > 0:47:05In the first ten years after they were moved to their new homes,
0:47:05 > 0:47:10only three chicks were reared. But then in the last two seasons,
0:47:10 > 0:47:14seven kakapo were successfully hatched.
0:47:14 > 0:47:19Maybe they will come back from the brink of extinction after all.
0:47:24 > 0:47:30Of course, only a minority of New Zealand's birds have become flightless.
0:47:30 > 0:47:37Most, like these spotted shags, have retained that characteristic talent of birds -
0:47:37 > 0:47:40the ability to travel by air.
0:47:40 > 0:47:45Worldwide, birds have exploited that ability to an extraordinary degree.
0:47:45 > 0:47:53Some can fly over 1,000 miles without landing, some can fly to altitudes of over 25,000 feet,
0:47:53 > 0:47:55some can even fly backwards.
0:47:55 > 0:48:00And how they manage to get into the air and sustain themselves there
0:48:00 > 0:48:04is what we will look at in the next programme.
0:48:43 > 0:48:48Subtitles by Gillian Frazer BBC Scotland 1998