0:01:18 > 0:01:25White Storks - if you wanted to pick one bird as representative of all birds in the world...
0:01:25 > 0:01:31you could do worse than pick the White Stork - a marvellous flier and an intrepid traveller.
0:01:31 > 0:01:37This pair have come from Africa to nest in this small town in Bavaria -
0:01:37 > 0:01:43they have complicated courtship and greeting rituals and they are devoted parents.
0:01:43 > 0:01:49Just as they could stand for all the birds, so this - a stork's feather -
0:01:49 > 0:01:54could be seen as a key to everything that is most crucial about a bird.
0:01:54 > 0:02:02A feather's a marvellous aerofoil - man has yet to invent anything as strong weight for weight.
0:02:02 > 0:02:08It's also an efficient insulator and that too, is important to a bird.
0:02:08 > 0:02:11It's a complicated structure.
0:02:11 > 0:02:18This feather has hundreds of filaments on either side of the central quill.
0:02:20 > 0:02:27They're held together by several hundred thousand microscopic hooks.
0:02:27 > 0:02:35The feather is the individual creation of the bird - no other animal possesses it.
0:02:36 > 0:02:45And the oldest known feather was found as a fossil in rocks a few miles from here in Bavaria.
0:02:45 > 0:02:51It's about 3 inches long, preserved in miraculous detail
0:02:51 > 0:02:56and to all intents and purposes, it looks identical with a stork's feather.
0:03:16 > 0:03:23That feather had been found by men quarrying this limestone near the town of Solhofen.
0:03:23 > 0:03:29The stones have been laid down 150 million years ago, at the bottom of a shallow lagoon.
0:03:29 > 0:03:35Its fine, even texture, made it ideal for use in lithographic printing.
0:03:35 > 0:03:44The texture also makes it a superb preserver of fossils and the feather tantalised the world of science.
0:03:44 > 0:03:52What could it have come from? Immediately there was a huge search mounted in the quarries.
0:03:52 > 0:04:00Even now it's almost impossible to resist the temptation of pulling down every boulder you see
0:04:00 > 0:04:10then opening it like a book to look at each page to see if it contains yet another fossil.
0:04:12 > 0:04:21After nearly a year, in 1851, in this very quarry, they found what they'd been looking for.
0:04:23 > 0:04:29A skeleton, a foot long, surrounded by feathers - Archaeopteryx - Ancient bird.
0:04:29 > 0:04:34Its skull was missing - but then, another complete skeleton was found.
0:04:34 > 0:04:42It had limbs of equal length, so but for the feathers it might have been a four-legged runner.
0:04:44 > 0:04:50Its head too, was very reptilian with tiny teeth along its bony jaw.
0:04:51 > 0:04:59The front limbs had three toes apiece - each toe ending with a claw.
0:05:01 > 0:05:07The tail was supported by a rod, an extension of the backbone running down the middle.
0:05:07 > 0:05:12All around are miraculously detailed impressions of feathers.
0:05:12 > 0:05:18In some places it's even possible to see the filaments on either side of a central quill.
0:05:18 > 0:05:25So those front limbs with claws are not the legs of a lizard, but the wings of a bird.
0:05:26 > 0:05:32So perfect are these fossils, we can make a confident reconstruction of the animal.
0:05:32 > 0:05:37But could this earliest of birds flap its wings?
0:05:37 > 0:05:44Its breastbone had no keel to carry muscles so its wing beats can only have been feeble.
0:05:44 > 0:05:48It probably depended for the most part on gliding.
0:05:50 > 0:05:54The long toes had a good grasp forwards and backwards.
0:05:54 > 0:05:58So it would've had no difficulty perching on branches.
0:05:58 > 0:06:02The claws on its wing helped it steady itself.
0:06:04 > 0:06:12In all the world today, there's only one creature with claws on its wings - and this is it:
0:06:16 > 0:06:23This is the Hoatzin - not an adult but a chick and it only has claws on its wing for a week or so
0:06:23 > 0:06:29but while it does, it gives a vivid hint of how the first birds may have moved in the trees.
0:06:45 > 0:06:50Maybe ancestors of Archaeopteryx took to trees because of hungry reptiles
0:06:50 > 0:06:53roaming below looking for a meal.
0:06:53 > 0:06:56The young Hoatzin faces just such dangers today.
0:06:56 > 0:07:03Its home in the swamps of Venezuela is haunted by crocodile and caiman,
0:07:03 > 0:07:08and reptiles very like them prowled the swamps and forests 150 million years ago.
0:07:17 > 0:07:23Although adult Hoatzin don't have claws on the wings, they do have a reptilian look
0:07:24 > 0:07:29with glittering eyes, surrounded with scaly skin and an odd, bristly crest.
0:07:31 > 0:07:37Nor have they totally mastered flight - they can only cover short distances.
0:07:39 > 0:07:44In the branches, they use their wings to help them keep their balance.
0:07:44 > 0:07:48But they're true birds, better adapted for flying
0:07:48 > 0:07:51than Archaeopteryx ever was.
0:07:51 > 0:07:54Fliers must reduce their weight to a minimum.
0:07:54 > 0:08:00All birds today, including the Hoatzin have lost the tail of the reptile and have a tail of feathers.
0:08:03 > 0:08:05Weight has been reduced in front -
0:08:05 > 0:08:08bony jaws and teeth are heavy -
0:08:08 > 0:08:11and no modern bird has them.
0:08:12 > 0:08:17Instead, they've beaks of keratin, the same horny substance as that from which feathers are made.
0:08:18 > 0:08:25Keratin is light and strong and can easily be moulded into a variety of shapes
0:08:25 > 0:08:30and turned into the particular tool the bird needs to gather its food.
0:08:32 > 0:08:35The Hoatzin has an unusual diet.
0:08:36 > 0:08:40It plucks leaves which it regurgitates for its chick.
0:08:57 > 0:09:01Often the beak is elongated and used as forceps.
0:09:01 > 0:09:06The White Stork can pick up frogs and little fish.
0:09:09 > 0:09:14The Shoebill has a heavy-duty version for dragging lungfish from mud.
0:09:14 > 0:09:18The Crane has a short pair to pick up seeds and insects.
0:09:19 > 0:09:27The butchers among birds have turned their beaks into hooks to tear flesh - Vultures.
0:09:31 > 0:09:35The Monkey-eating Eagle from the Philippines.
0:09:42 > 0:09:50Others, like the Scarlet Ibis, have long probes that can pick small invertebrates from burrows.
0:09:54 > 0:10:02The beak of a Spoonbill isn't a spoon but a sieve which collects small creatures from the water.
0:10:07 > 0:10:16A Flamingo's bill is a filter-pump - the tongue's a piston drawing water in and squirting it out.
0:10:16 > 0:10:25Coarse hairs on the side prevent mud getting in and hairs inside trap microscopic plants and animals.
0:10:26 > 0:10:28Pelicans.
0:10:32 > 0:10:37Some dive on shoals of fish - others use their bills as nets.
0:10:38 > 0:10:41They fish in teams.
0:10:55 > 0:10:58Another fisherman.
0:10:59 > 0:11:03Little fish swim into the shade.
0:11:03 > 0:11:06The Black Heron provides it with its wings
0:11:06 > 0:11:09and then stabs with precision at any fish that's attracted to it.
0:11:11 > 0:11:14The beak's not only a feeding tool
0:11:16 > 0:11:21it's an essential instrument for keeping in trim the feathers.
0:11:21 > 0:11:24They need a lot of maintenance if they're to be kept in good condition.
0:11:24 > 0:11:29The beak is used with great delicacy to preen the feathers,
0:11:29 > 0:11:35repairing any breaks by zipping up the hooks on the filaments.
0:11:52 > 0:11:57Storks, like most birds, have a preen gland on their rump.
0:11:57 > 0:12:03They collect oil with their beak and use it to waterproof their feathers.
0:12:07 > 0:12:11Waterproofing is specially important for water birds...
0:12:11 > 0:12:15and water flows off a duck's back because its feathers are well-oiled.
0:12:29 > 0:12:32But being waterproof makes problems.
0:12:33 > 0:12:36Below water, unwetted feathers hold air like a silver sheath.
0:12:36 > 0:12:42It's very buoyant, so ducks and ducklings must paddle hard
0:12:43 > 0:12:45or they bob back.
0:13:06 > 0:13:09The business of getting the beak into the mud
0:13:09 > 0:13:16is made easier by having the legs back near the tail - all the same, it's hard work.
0:13:50 > 0:13:53As well as oiling feathers
0:13:53 > 0:13:57many birds, like the Peacock, ruffle them in dust.
0:13:57 > 0:14:03The skin beneath the feathers makes an attractive home for parasites like fleas and lice.
0:14:03 > 0:14:06This gets rid of them.
0:14:06 > 0:14:13Another way is to enlist the help of other insects - ants.
0:14:13 > 0:14:16Ants, when irritated, squirt acid and that shifts most insect parasites.
0:14:19 > 0:14:23Jays and Crows are addicted to this habit.
0:14:36 > 0:14:40By spreading its wings, the bird makes it easy for angry ants
0:14:40 > 0:14:43to swarm over its skin between the feathers.
0:14:43 > 0:14:46Often the bird enjoys it so much
0:14:47 > 0:14:50it goes into a kind of ecstasy.
0:15:09 > 0:15:15So, one way or another, birds go to a lot of trouble to keep their feathers in good condition.
0:15:15 > 0:15:19In truth, their lives depend on them - and not just for support in the air.
0:15:19 > 0:15:23Birds are warm-blooded.
0:15:26 > 0:15:32So insulation for their bodies is essential - and nothing does it better than a coat of feathers.
0:15:35 > 0:15:38Only a bird in a coat of feathers...
0:15:38 > 0:15:42..can live in the coldest place on Earth - the Antarctic in winter.
0:15:51 > 0:15:58Some species of Penguin survive at 40 degrees below freezing for weeks on end.
0:16:09 > 0:16:12The feathers of adult and chick
0:16:12 > 0:16:17are adapted to provide warmth - fine and in a thick mat.
0:16:17 > 0:16:23But the feathers of most birds serve another purpose as well - flight.
0:16:23 > 0:16:28If beauty comes from perfection, grace a measure of skill,
0:16:28 > 0:16:33then a bird in the air must be one of the loveliest sights in nature.
0:17:14 > 0:17:20Terns are among the most graceful of fliers, responding to every variation of wind currents
0:17:20 > 0:17:25with subtle adjustments to the contours of tail and of wings.
0:17:51 > 0:17:59The Tropic bird uses updraughts and works hard to hang in the air to display to its mate.
0:18:12 > 0:18:20Ocean-going birds like the Frigate sail on long thin wings - the best shape for efficient gliding.
0:18:26 > 0:18:30One of the most skilled gliders of all - the Albatross.
0:18:30 > 0:18:37It beats up and down the ocean, supported by the lightest of breezes with only gentle flaps of its wings.
0:18:50 > 0:18:55But long wings for easy flight don't make for easy landings.
0:19:07 > 0:19:15Having missed its touchdown, the Booby labours to regain speed and avoid a stall and a crash.
0:19:27 > 0:19:33The Frigate has similar problems, but solves them successfully.
0:19:41 > 0:19:45The Booby has another try.
0:19:57 > 0:20:02There are helpful winds to be exploited over land as well as sea.
0:20:02 > 0:20:08Above wild, mountainous country, like the Grand Canyon, the sun heats the naked rock.
0:20:09 > 0:20:12There are hot currents sweeping up...
0:20:12 > 0:20:18so vultures can sail and soar with an economy that rivals that of the Albatross.
0:20:27 > 0:20:33Such birds sliding effortlessly though the air, can reach great speeds.
0:20:33 > 0:20:37But the airspeed record is held by a much smaller flier...
0:20:37 > 0:20:42..the Swift - here it's in slow motion.
0:20:42 > 0:20:48One species can reach speeds of 170 kms an hour.
0:20:48 > 0:20:55The Swift - most aerial of birds, hardly alighting except to nest, mating and sleeping on the wing...
0:20:55 > 0:20:58..flying up to 1,000 kms a day...
0:20:59 > 0:21:01..to gather insects from the air.
0:21:01 > 0:21:08Others feed on the wing and just as ground feeders have beaks modified for their diets...
0:21:09 > 0:21:15..so many of these hunters have beaks specially suited to their own techniques.
0:21:15 > 0:21:19What's more, ones that require acrobatic skill to manage properly.
0:21:21 > 0:21:24The Skimmer has the oddest.
0:21:24 > 0:21:31It's the only bird with the lower mandible longer than the upper - to use it needs perfect control.
0:21:39 > 0:21:44When the lower mandible strikes an object, the beak snaps shut.
0:21:47 > 0:21:50There may be more to it than that.
0:21:51 > 0:21:57The furrow in the surface of the water sparkles and attracts surface-feeding fish.
0:21:57 > 0:22:03Having made one run, the Skimmer turns and flies back along the same course.
0:22:03 > 0:22:08Perhaps to collect anything that has taken the lure.
0:22:33 > 0:22:41In the Andes live other birds with superb aerial control and extraordinary beaks to manipulate.
0:22:41 > 0:22:45The Datura plant is rich in nectar and humming birds love it.
0:22:47 > 0:22:52But those with normal-sized bills can't reach the main supply at the top of the tubular blossom,
0:22:52 > 0:22:55even when they cling to the flowers with their feet.
0:23:02 > 0:23:06The Sapphire-Wing has a longer bill.
0:23:10 > 0:23:14Even this can't reach the depths of the flowers.
0:23:18 > 0:23:20What's needed is this -
0:23:20 > 0:23:24the beak of the Swordbilled hummingbird
0:23:24 > 0:23:27longer than its entire body.
0:23:27 > 0:23:30The flying control has to be total
0:23:30 > 0:23:34to manoeuvre this huge instrument, and it is.
0:23:34 > 0:23:39Slow motion shows its expertise at keeping its bill perfectly steady
0:23:39 > 0:23:41in relation to the blossom,
0:23:41 > 0:23:46even while its body moves in all directions.
0:23:52 > 0:23:59Slowed right down, you can see how the wings move to enable the bird to hang in the air.
0:23:59 > 0:24:05The bird tips its body vertically so air currents from the wings are driven downwards.
0:24:05 > 0:24:12Each wing's so jointed, it beats in a figure of 8 and gives lift on both forward and backward beat.
0:24:12 > 0:24:16Their arms are short and close to the body,
0:24:16 > 0:24:20so they actually fly with their hands.
0:24:34 > 0:24:37So with the help of feathers
0:24:38 > 0:24:42birds have mastered all manoeuvres in the air.
0:24:42 > 0:24:47The stork flies up from Africa to Europe in spring to nest,
0:24:47 > 0:24:53often on the same site it's used many times before.
0:25:05 > 0:25:11The male usually arrives first and proclaims his ownership of the site.
0:25:19 > 0:25:28The nest's refurbished - no matter how big it is, the bird improves it with sticks and a fresh lining.
0:25:32 > 0:25:36This display is not only a notice of possession, but is also an invitation to a mate.
0:25:36 > 0:25:42BILLS CLATTER
0:25:42 > 0:25:49Once they've come together, the ritual's carried out again and again strengthening bonds between them.
0:25:49 > 0:25:53The sound of the bill-clatter is an integral part of the display.
0:25:56 > 0:26:00The Nightingale also needs a mate and a nesting site...
0:26:00 > 0:26:07but its feathers are drab, its habits retiring, and it claims them with a song
0:26:07 > 0:26:11a song that penetrates the thickets where it lives.
0:26:37 > 0:26:41Song, like bright feathers, conveys a third message - identity.
0:26:46 > 0:26:50A relative of the nightingale - the Blackcap.
0:26:50 > 0:26:55He makes his species clear with that distinctive patch of black on his head.
0:26:55 > 0:26:59But he produces a quite different, and very characteristic song.
0:27:08 > 0:27:12The Grasshopper Warbler relies almost entirely on song.
0:27:12 > 0:27:15A rival is singing and he must answer.
0:27:52 > 0:28:00This looks a Grasshopper Warbler and birdwatchers and birds can't be sure it isn't till it sings.
0:28:04 > 0:28:07It's a Willow Warbler.
0:28:07 > 0:28:14So with song and dance, identities are established, territories claimed and the pair bond made.
0:28:19 > 0:28:24All is set for the business of reproduction.
0:28:48 > 0:28:51Feathers are well suited for display.
0:28:52 > 0:28:58They're light, can be easily erected into fans and crests, and some birds
0:28:59 > 0:29:04like the Kori Bustard, have exploited that potential to an extraordinary degree.
0:29:04 > 0:29:10When male meets male on the African plains, they argue over territory with feathers.
0:29:22 > 0:29:28The female Great Bustard is neatly camouflaged and unobtrusive
0:29:28 > 0:29:33but her mate inflates himself in a most spectacular fashion.
0:29:35 > 0:29:38One family excels in the shape,
0:29:38 > 0:29:45colour and beauty of its feathers - New Guinea's Birds of Paradise.
0:30:26 > 0:30:30The Superb bird has an iridescent sheen on its chest
0:30:30 > 0:30:35and a roll of feathers it can open like an umbrella.
0:30:37 > 0:30:45The Six-Wired birds carry six naked quills on their heads, each ending in a black pennant.
0:30:46 > 0:30:53The males display on the ground, clearing special dancing floors, which they keep meticulously clean.
0:31:02 > 0:31:05The female hasn't his splendour.
0:31:05 > 0:31:13The male's life in the breeding season is devoted to dancing - she mates with one of the dandies.
0:31:13 > 0:31:15She rears the young by herself,
0:31:15 > 0:31:19while he continues to strut on his court.
0:31:19 > 0:31:21The Magnificent bird has two quills
0:31:22 > 0:31:26and three capes of different colours.
0:31:28 > 0:31:33He too, displays on the ground and strips the leaves so he can dance in a pool of light.
0:31:35 > 0:31:39Other Birds of Paradise display in the branches.
0:31:39 > 0:31:47Males don't acquire plumes until they're older and moult at the end of the breeding season.
0:31:47 > 0:31:50So mostly they're like their drab females.
0:31:50 > 0:31:56When dressed for the dance however they spend a lot of time grooming and preening themselves.
0:31:56 > 0:32:05They lavish as much care on their display feathers as they do on the utility ones - those for flight.
0:32:17 > 0:32:22Females visit the display trees to select partners
0:32:22 > 0:32:26but males display whether they are there or not.
0:32:52 > 0:32:57Each species - this is a Lesser bird - has its own dance
0:32:57 > 0:33:02its own way of showing off its finery to the best advantage.
0:33:11 > 0:33:17The Emperor of Germany's bird begins by fluffing up the plumes beneath its wings
0:33:17 > 0:33:22but has developed a most surprising climax to his performance.
0:33:39 > 0:33:45Count Raggi's bird throws his plumes over his back in a quivering fountain of red.
0:33:51 > 0:33:55But the most remarkable display is that of the Bluebird.
0:34:11 > 0:34:17As he quivers, he sings as extraordinary and unbirdlike a song
0:34:17 > 0:34:19as comes from any bird.
0:34:58 > 0:35:05These are among the largest feathers and the most spectacular - the Peacock's feathers.
0:35:05 > 0:35:10They're still something of a mystery - Darwin was baffled
0:35:10 > 0:35:14by the sheer perfection of such feathers as these.
0:35:14 > 0:35:20Are they just to help him compete?
0:35:20 > 0:35:22Or to impress the Peahen?
0:35:22 > 0:35:29There are people who think we've some way to go before we know the answer to questions like those.
0:35:44 > 0:35:51This is one characteristic of the reptiles, birds never abandoned - laying eggs in nests.
0:35:51 > 0:35:58Every other vertebrate group has species that retain eggs in the body and give birth to live young.
0:35:58 > 0:36:08Some fish, amphibians, reptiles and all mammals, but not a single bird does - the reason's obvious.
0:36:08 > 0:36:16It would be a severe handicap for a bird to fly with the weight of this or a whole clutch
0:36:16 > 0:36:20for as long as it takes for it to hatch.
0:36:20 > 0:36:29Much better to lay it in a nest as soon as it forms - but that makes the eggs very vulnerable.
0:36:29 > 0:36:35Birds go to a lot of trouble to protect their eggs and their nests.
0:36:39 > 0:36:49The peahen nests in undergrowth and foregoes the display feathers of her mate so she's well camouflaged.
0:36:53 > 0:37:00Some waterbirds such as the Giant Coot in Chile, lay eggs on islands of vegetation.
0:37:00 > 0:37:04Beyond the reach of nest robbers.
0:37:19 > 0:37:24Other birds, like the Oropendolas from South America, achieve inaccessibility
0:37:24 > 0:37:29by weaving bottle nests on branches.
0:37:31 > 0:37:34On the pampas of South America, the Oven birds build with mud.
0:37:35 > 0:37:43It's shaped like a local oven and when finished has a tiny entrance which foils most intruders.
0:37:49 > 0:37:54Longtailed Tits weave a domed nest of cobwebs and moss...
0:37:54 > 0:38:01fill it inside with downy feathers and camouflage it with lichen.
0:38:02 > 0:38:11The Sparrow is an untidy builder and makes use of sticks, including those from other nests.
0:38:25 > 0:38:29In Iceland, there are great colonies of Arctic Terns.
0:38:29 > 0:38:34The shores where they nest provide little building material and no cover whatsoever.
0:38:34 > 0:38:41So they dispense with nests and do their best to deflect intruders by diving at them.
0:38:43 > 0:38:48The safety of their eggs depends largely on their camouflaged shells.
0:38:48 > 0:38:53Inside the eggs, developing chicks like parents, have warm blood
0:38:53 > 0:38:56and if they get chilled, they die.
0:38:56 > 0:39:02The Eider Duck, which also breeds in Iceland, develop special downy feathers on the breast
0:39:02 > 0:39:07and with them, builds one of the warmest of all nests.
0:39:11 > 0:39:17Man himself has yet to devise anything more luxuriously warming than eider down.
0:39:17 > 0:39:22The colour of eggs varies - and so does the size.
0:39:22 > 0:39:29This is the smallest of all, laid by a Hummingbird and no bigger than a pea - and this is the biggest.
0:39:31 > 0:39:41It's the largest egg it's possible to have - the shell has to be thick to hold two gallons of liquid.
0:39:41 > 0:39:49If it were any bigger, it might have been so thick the chick might not be able to hammer its way out.
0:39:49 > 0:39:54This egg was found here in the thorn forests of Madagascar.
0:39:54 > 0:40:04It was laid by a giant flightless bird, the biggest ever, like the Ostrich - about 10 feet tall.
0:40:05 > 0:40:15It was the Elephant bird and was alive up to 200-300 years ago, but now, alas, extinct.
0:40:18 > 0:40:26Birds have to work hard keeping them warm in the cold or protecting them from the sun.
0:40:27 > 0:40:34When the eggs hatch, they must collect food for the growing and perpetually hungry young.
0:40:37 > 0:40:44Soon these storks will fly - but where exactly will they go?
0:40:44 > 0:40:49To find out, stork-chicks all over Europe have been ringed.
0:41:12 > 0:41:16The rings are light and aluminium with an address,
0:41:16 > 0:41:21so anyone finding the bird will know where it was hatched and reared.
0:41:24 > 0:41:31The young storks flap their wings, exercising the muscles that will sustain them in the air,
0:41:31 > 0:41:36while their parents collect daily supplies of frogs and fish.
0:41:47 > 0:41:50In 60 days, young and old depart.
0:41:50 > 0:41:57The chicks have most of the skills of flying the very first time they launch into the air.
0:42:08 > 0:42:13Some surprising results have come from ringing storks in this town in southern Germany.
0:42:13 > 0:42:19Many make their way to Africa going east round the Mediterranean by way of Istanbul.
0:42:19 > 0:42:26The town lies on a fork in the migration route - others go west across the Straits of Gibraltar.
0:42:26 > 0:42:30As they head south they become more concentrated.
0:42:30 > 0:42:35These journeys make great demands on a bird's strength.
0:42:36 > 0:42:42Many rely on upward-rising thermal currents produced when the sun heats the land.
0:42:42 > 0:42:47If you can get high, you can glide effortlessly for great distances.
0:42:47 > 0:42:56Thermals don't occur over the sea so birds gain as much height as they can before crossing the Med.
0:42:56 > 0:43:03Near Gibraltar and Istanbul they soar round and round in up-currents climbing higher and higher.
0:43:04 > 0:43:08Those that arrive in the evening, roost.
0:43:08 > 0:43:14After the sun's gone, there are no more thermals and it's better to wait till morning.
0:43:30 > 0:43:38The Straits of Gibraltar in spring and autumn are visited by thousands on the way to or from Africa.
0:43:38 > 0:43:43Nearby mountains and the Rock warming in the sun
0:43:43 > 0:43:51produce strong up-currents of air - and Africa lies only a few kilometres away across the Straits.
0:43:52 > 0:43:55A Kestrel, resting on its journey.
0:43:59 > 0:44:05Honey Buzzards from much of Europe congregate here and share thermals with Storks.
0:44:20 > 0:44:24These invasions of "tourists" infuriate local residents.
0:44:24 > 0:44:29Some days Short-toed Eagles can't get the lift they need.
0:44:31 > 0:44:35They fly round the Harbour and local gulls mob them.
0:44:37 > 0:44:45Sometimes they drive them into the water and they can't take off again - another hazard of migration.
0:44:53 > 0:44:58A Black Kite on its way to Africa after breeding in Europe.
0:44:58 > 0:45:02September in Gibraltar is a marvellous place for a birdwatcher,
0:45:02 > 0:45:06as travellers meet at this migration crossroads.
0:45:06 > 0:45:10The best place to watch is from the top of the Rock.
0:45:14 > 0:45:18It's coming to the end of the day and it's been a good one for the migrants.
0:45:18 > 0:45:23Parties of big birds, 30, 40 or 50 strong, have been passing the Rock...
0:45:23 > 0:45:27gathering to get a last lift from a thermal in Europe
0:45:27 > 0:45:34so they can glide down across the Straits to Africa 12 miles away.
0:45:34 > 0:45:36How did they find their way here?
0:45:36 > 0:45:42Some undoubtedly use geographical landmarks and come along the coast.
0:45:42 > 0:45:48Others use prominent river valleys - but that can't be all there is to it.
0:45:48 > 0:45:52Young birds that have never made the journey manage it alone.
0:45:52 > 0:45:58So presumably, they have some kind of inherited map in their minds.
0:45:58 > 0:46:07Others use the sun in some way - they can cross large expanses of sea and featureless land.
0:46:07 > 0:46:12But the sun has a major drawback as a navigational aid - it moves.
0:46:12 > 0:46:17So, to find your way by it, you must know what the time is.
0:46:17 > 0:46:21So these birds must also have a clock in their minds.
0:46:21 > 0:46:24But in the evening
0:46:24 > 0:46:26the sun goes down and it gets dark,
0:46:26 > 0:46:31you may no longer be able to see landmarks - what happens then?
0:46:34 > 0:46:39The answer can be found here in the Air Traffic Control Tower at the Rock.
0:46:39 > 0:46:44Gibraltar's important to defence in Western Europe
0:46:44 > 0:46:49and watch is kept by radar on aircraft movements around it.
0:46:49 > 0:46:54But radar can show flocks of birds as well as aircraft.
0:46:54 > 0:46:59In autumn and spring the information from these screens,
0:46:59 > 0:47:03about the sky at night is spectacular indeed.
0:47:06 > 0:47:11A few hours of an autumn night can be condensed to a few seconds.
0:47:11 > 0:47:19The number of birds crossing into Africa can be estimated from the mass of dots moving south-west.
0:47:19 > 0:47:24On this night up to 200,000 birds at one time are represented on the screen.
0:47:24 > 0:47:29It's estimated 5,000 million cross the Mediterranean each autumn.
0:47:34 > 0:47:37How do they find their way?
0:47:37 > 0:47:38Some birds fly by the stars
0:47:38 > 0:47:42and if you release them in a Planetarium
0:47:42 > 0:47:48where artificial stars have been twisted around, they fly by those.
0:47:48 > 0:47:52Other birds are sensitive to electro-magnetic waves.
0:47:52 > 0:47:58So it appears a bird must not only have a map, a star chart and a clock
0:47:58 > 0:48:01but a compass in its mind.
0:48:01 > 0:48:08The fact is there's a great deal we don't know about bird navigation.
0:48:08 > 0:48:12Gibraltar's a half-way stage for most migrants -
0:48:12 > 0:48:16Arctic Terns hatched in July are here in September.
0:48:18 > 0:48:23They've still 10,000 kms to go before reaching their destination.
0:48:24 > 0:48:26Shearwaters move in a different direction,
0:48:26 > 0:48:30migrating east and west between the Mediterranean and the Atlantic.
0:48:30 > 0:48:37They're great travellers - one was back in its nest in Wales after crossing the Atlantic in 12 days.
0:48:41 > 0:48:45This Arctic Tern has reached the southern tip of South America.
0:48:45 > 0:48:48It left the Arctic at the end of its summer when the sun never set,
0:48:48 > 0:48:51it's flying to an Antarctic summer.
0:48:51 > 0:48:56So it sees more daylight than any other creature.
0:48:58 > 0:49:02The African plains are the target for Storks.
0:49:02 > 0:49:05By the end of September, they're among game
0:49:05 > 0:49:09as they were among herds of dairy cows a few weeks earlier.
0:49:11 > 0:49:17So flight, birds' great achievement has carried them not only to all parts of the world
0:49:17 > 0:49:20but makes them the greatest of animal travellers.
0:49:20 > 0:49:23Yet, most surprisingly
0:49:23 > 0:49:26some species have abandoned it.
0:49:26 > 0:49:30There's no doubt ostriches' ancestors could fly.
0:49:30 > 0:49:34It still has a beak instead of teeth and jaws,
0:49:34 > 0:49:38and feathers in patterns needed for flight.
0:49:38 > 0:49:42Now the feathers are used only for display.
0:49:56 > 0:50:02The feathers no longer support the bird in the air, so the hooks on the filaments have disappeared.
0:50:02 > 0:50:08The feathers have a soft fluffiness that is found to be alluring by other creatures.
0:50:46 > 0:50:50Why should the ancestral ostrich have given up flight?
0:50:50 > 0:50:52Well, it's a demanding business.
0:50:52 > 0:50:59If there are no predators to drive birds into the air, it's easier to remain on the ground.
0:50:59 > 0:51:06That happens today on islands and it happened once to ancestral ostriches.
0:51:12 > 0:51:18Ostriches belong to one of the most ancient of bird families.
0:51:18 > 0:51:21They appeared 50 million years ago
0:51:21 > 0:51:27when dinosaurs and other giants had only recently vanished.
0:51:27 > 0:51:30The position of ruler of the world was vacant
0:51:30 > 0:51:35and it seems that birds like that, made a bid for it.
0:51:35 > 0:51:37There was one
0:51:37 > 0:51:45a flightless bird in America with a huge bill which could have killed any animal around.
0:51:45 > 0:51:48Even looking at ostriches
0:51:48 > 0:51:56you see how dangerous they might be if they suddenly acquired a taste for red meat.
0:51:56 > 0:52:04They could outrun me and one kick from those legs could knock me over and rip me open.
0:52:04 > 0:52:11But that bid for supremacy failed - there was another, unobtrusive creature around at the time...
0:52:11 > 0:52:17that also had warm blood but was descended from a different group of reptiles from the birds...
0:52:17 > 0:52:21and it insulated its body, not with feathers, but with fur.
0:52:21 > 0:52:26That was the creature whose descendants would inherit the Earth,
0:52:26 > 0:52:28that was the first mammal.
0:53:06 > 0:53:10Subtitles by Red Bee Media Ltd