"as a representative of all the birds in the world, you could do worse than pick the white stork." "It's a marvellous flyer, an intrepid traveller." "This pair will have come from Africa to nest in this small town in Bavaria." "They have complicated courtship and greeting rituals and they're devoted parents." "Just as they could stand for all the birds in the world, so this, a stork's feather, could be seen as a key to everything that is most crucial about a bird." "The feather is a marvellous aerofoil." "Man has yet to invent anything as strong, weight for weight." "It's also an extremely efficient insulator, and that too is important to the bird." "And it's a very complicated structure." "This feather has several hundred separate filaments on either side of the central quill." "They are held together to form one continuous surface by several hundred thousand microscopic hooks." "The feather is the individual creation of the birds." "No other kind of animal possesses it." "And the oldest known feather in the world was discovered as a fossil in the rocks only a few miles from here in Bavaria." "It's two and three-quarter inches long, preserved in miraculous detail, and to all intents and purposes it looks identical with a stork feather." "That feather had been found by men quarrying limestone near the little town of Solenhofen." "The stone had been laid down about 150 million years ago at the bottom of a shallow lagoon, and its fine, even texture made it ideal for use in lithographic printing." "But that texture also makes it a superb preserver of fossils." "The feather tantalised the world of science." "What sort of creature could it have possibly come from?" "Well, immediately, there was a huge search mounted in these quarries." "Even now, it's almost impossible to resist the temptation of pulling down almost every boulder you see and then opening it like a book to look at each unopened page to see whether maybe..." "it contains yet another fossil." "And after nearly a year, in 1861, in this very quarry, they found what they'd been looking for." "A skeleton a foot or so long surrounded by feathers." "They called it archaeopteryx, "ancient bird"." "Its skull was missing, but then another complete skeleton was found." "The creature had limbs of equal length, so if it weren't for the feathers, it might have been taken for a four-legged runner, like a lizard." "Its head too, was veru reptilian, with tiny teeth along its bony jaws." "The front limbs had three toes apiece, each toe ending with a claw." "The tail was supported by a bony rod, an extension of the backbone running down the middle." "But all around, there are the miraculously detailed impressions of feathers." "In some places, it's possible to see the filaments on either side of a quill." "So those front limbs with claws are not the legs of a lizard, but the wings of a bird." "So perfect are these fossils that we can make a pretty confident reconstruction of the living animal" "But could this, the earliest of birds, flap its wings?" "Its breastbone has no keel on it to carry large muscles, so its wing-beats at best could only have been feeble." "It probably depended for the most part on gliding." "The long toes on its feet had a good grasp both forwards and backwards, so it would have had no difficulty in perching on branches." "And those claws on its wing doubtless helped it to steady itself as it clambered around." "In all the world today, there is only one living creature with claws on its wings." "And this is it." "This is the hoatzin." "Not an adult bird, but a chick." "It only possesses claws on its wings for a week or so." "While it does, it gives a vivid hint of how the first birds may have moved about in their trees." "Maybe the ancestors of archaeopteryx took to the trees because hungry reptiles roamed below looking for a meal." "The young hoatzin faces just such dangers today, for its home in the swamps of Venezuela is haunted by crocodiles and cayman." "And reptiles very like them prowled swamps and forests 150 million years ago." "Although the adult hoatzins don't have claws on their wings, they nevertheless still have a very reptilian look to them, with their glittering eyes surrounded with scaly skin and an odd, bristly crest." "Nor do they seem to have totally mastered flight." "They can only cover relatively short distances before they need a rest." "In the branches, they use their wings to help them keep their balance." "Nonetheless they are true birds and very much better adapted for flying than archaeopteryx ever was." "Flyers must reduce their weight to a minimum, and all birds today, including the hoatzin, have lost the bony tail of the reptile and have instead a lightweight tail constructed entirely of feathers." "Weight has been reduced at the front end as well." "Bony jaws and teeth are particularly heavy, and no modern bird possesses them." "Instead, they have beaks of keratin, the same horny substance as that from which feathers are made." "Keratin is not only light and strong, but it can easily be moulded into a great variety of shapes and turned into the particular tool that a bird needs to gather its food." "The hoatzin has an unusual diet." "It uses its beak to pluck leaves, which it then regurgitates for its chick." "Often the beak is elongated and used as a pair of forceps." "The white stork has a medium-sized model for picking up frogs and little fish." "Another stork, the shoebill, has a heavy-duty version for dragging lungfish from mud, and the crane a short pair with which to pick up seeds and insects." "The butchers among birds have turned their beaks into hooks with which to tear flesh: vultures." "The monkey-eating eagle from the Philippines." "Others, like the scarlet ibis, have long probes that can pick out small invertebrates from their burrows." "The beak of a spoonbill is not in fact a spoon but a sieve, with which its owner collects small creatures from the water." "The flamingo's bill is a filter pump." "The tongue works like a piston, drawing water in and squirting it out several times a minute." "Coarse hairs on the side of the bill prevent mud getting in, and hairs inside trap microscopic plants and animals." "Pelicans." "Some dive on shoals of fish." "Others use their baggy bills as nets, and go fishing in teams." "Another fisherman." "Little fish, it seems, are eager to swim into the shade." "The black heron provides it with its wings and then stabs with precision at any fish that attracted to it." "The beak is not only a feeding tool." "It's also an essential instrument for keeping in trim those most valuable of a bird's possessions, its feathers." "They need a lot of maintenance if they to be kept in the best of condition, and the beak, even the biggest, is used with great delicacy to preen the feathers one by one, repairing any breaks in their veins by zipping up the hooks on the filaments." "Storks, like most birds, have a preen gland on their rump." "They collect oil from it with their beaks and use that to waterproof their feathers." "Waterproofing is obviously particularly important for waterbirds, and water only flows off a duck's back because its feathers are well oiled." "But being waterproof does cause problems." "Below water, unwetted feathers hold air trapped between them like a silver sheath, and that's very buoyant, so ducks and ducklings have to paddle hard with their legs to prevent themselves from bobbing back to the surface." "The business of getting the beak down into the mud of the bottom is made easier by having legs far back on the body, near the tail." "All the same, it's hard work." "As well as oiling their feathers, many birds, like the peacock, ruffle them in dust." "The skin beneath the feathers must make it a very attractive home for parasites like fleas and lice, and dust bathing helps get rid of them." "Another way is to enlist the help of other insects: ants." "Many ants, when irritated, squirt acid, and that will shift most insect parasites." "Jays and crows are particularly addicted to this habit." "By spreading its wings, the bird makes it easier for angry ants to swarm all over its skin between the feathers." "And often, the bird seems to enjoy the process so much that it goes into a kind of ecstasy." "So one way or another, birds go to a lot of trouble to keep their feathers in good condition." "In truth, their lives depend on them, and not only for support in the air." "Birds are warm-blooded." "They have to be to produce the energy they need for their very active lives." "So insulation for their bodies is essential, and nothing does it better than a coat of feathers." "Only a bird wrapped in a coat of fine feathers can live in the coldest place on earth:" "the Antarctic ice cap in winter." "Some species of penguin survive temperatures of 40 degrees below freezing." "And for weeks on end." "The feathers of both adult and chick are specially adapted to provide warmth." "They're very fine and grow in a thick mat." "But the feathers of most birds have to serve another purpose as well: flight." "If beauty comes from perfection, if grace is a measure of skill, then a bird in the air must be among the loveliest sights in nature." "Terns are among the most graceful of flyers, responding to every tiny variation in the wind currents with subtle adjustments to the contours of the tail and wings." "The tropic bird, by using updraughts and working hard, can hang in the air in order to display it to its mate." "Ocean-going birds like the frigate sail on long, thin wings, the best shape for efficient gliding." "One of the most skilled gliders of all, the albatross, which beats up and down the ocean supported by the lightest of breezes with only the gentlest of flaps of its wings." "But long wings for gliding flight don't make for easy landings." "Having missed its touchdown, the booby has to labour to regain speed and avoid a stall and a crash." "The frigate bird has similar problems but solves them successfully." "The booby has another try." "There are helpful winds to be exploited over land as well as over the sea, and above wild, mountainous country like the Grand Canyon where the sun heats the naked rock, there are hot thermal currents that sweep up the cliff faces." "So vultures can sail and soar with an economy that rivals that of the albatross." "Such birds as these, sliding effortlessly through the air, can reach great speeds." "But the airspeed record is held by a much smaller flyer." "The swift." "Here, it is in slow motion." "One species is said to reach speeds in level flight of 170km an hour." "The swift is the most aerial of birds, hardly ever alighting except to nest, mating and even sleeping on the wing, and every day flying up to 1,000km a day, to gather insects from the air." "Other birds also feed on the wing, and just as ground feeders have beaks modified for their particular diets, so many of these flying hunters have beaks suited to their own techniques." "And what's more, ones that require great acrobatic skill to manage properly." "The skimmer has the oddest of beaks." "It's the only bird with the lower mandible longer than the upper." "And to use it requires perfect flight control." "When the lower mandible strikes an object like a fish, the beak automatically snaps shut." "Some say there's more to it than that." "The furrow cut in the surface of the water sparkles and attracts surface-feeding fish." "Having made one run, the skimmer often turns and flies back along exactly the same course, perhaps to collect anything that has taken the lure." "In the Andes live other birds with superb aerial control and extraordinary beaks to manipulate." "The detura plant is rich in nectar, and hummingbirds are nectar addicts." "But those with normal-sized bills can't reach the main supply at the top of the blossoms, even when they cling to the flowers with their feet." "The sapphirewing has a somewhat longer bill." "But even this can't reach into the depths of the flowers." "What is needed is this." "The outsize beak of the sword-billed hummingbird, that is longer than its entire body." "The bird's flying control has to be total to manoeuvre this huge instrument, and it is." "Slow motion shows how expert it is in keeping its bill perfectly steady in relation to the blossom, even while its body moves in all directions." "Slowed down still further, you can see how the wings move in order to enable the bird to hang in the air." "The bird tips its body vertically so that air currents from the wings are driven downwards." "Each wing is so jointed, it beats in a figure of eight and produces lift on both the forward and the backward beat." "Their arms are short and close to the body, so these birds actually fly with their hands." "So, with the help of their feathers, birds have mastered all the manoeuvres in the air." "The stork's wings carry it for thousands of miles up from Africa to Northern Europe each spring to nest." "Often on exactly the same site it's used many times before." "The male usually arrives first and immediately proclaims ownership of the site." "The nest must be refurbished." "No matter how big it is already, the bird seems to think it'll be improved with a few more sticks and a fresh lining." "(CLATTERING)" "This display not only serves as a notice of possession." "but as an invitation to a mate." "Once the pair have come together, the ritual is carried out again and again, strengthening the bond between them." "The sound of the bill clatter is an integral part of the display." "The nightingale also needs a mate and a nesting site, but its feathers are drab, its habits retiring, and it claims them not with a dance and a clatter but with a song." "A song that penetrates the thickets in which it lives." "(CHIRPING)" "Song, like bright feathers, conveys a third message:" "identity." "(LIVELY CHIRPING)" "This is a relative of the nightingale, the blackcap." "He makes his species clear with that patch of black on his head." "He also produces a quite different and very characteristic song." "The grasshopper warbler relies almost entirely on song." "That's a rival singing and he must answer." "(LOW-PITCHED WHIRRING)" "(SIMILAR SOUND IN DISTANCE)" "This looks like another grasshopper warbler, and most birdwatchers, and most birds, couldn't be quite sure it isn't until it sings." "(HIGH-PITCHED CHIRPING)" "It's a willow warbler." "So, with song and dance, identities are established, territories claimed and the pair bond made." "All is now set for the business of reproduction." "Feathers are particularly suited for display." "They're light, they can be easily erected into great fans and crests, and some birds like for example the cory bustard have exploited that potential to an extraordinary degree." "When male meets male on the African plains, they argue over territory with feathers." "The female great bustard is neatly camouflaged and unobtrusive." "But her mate inflates himself in the most spectacular fashion." "But one family has excelled all others in the shape, the colour, the sheer beauty of their display feathers." "They live in New Guinea." "The birds of paradise." "This superb bird not only has an iridescent shield on its chest, but on the nape of its neck a roll of feathers it can open into an umbrella." "The six-wired birds, and there are several kinds, carry half a dozen naked quills on their heads, each ending in a small black pennant." "The males display on the ground, clearing special dancing floors which they tend every day, keeping them meticulously clean and tidy." "The female has none of the splendour of the male." "His life during the breeding season is devoted to dancing." "The females tour the courts and eventually mate with one of these dandies." "She rears the young entirely by herself while he continues to strut on his court." "The magnificent bird sprouts two curling quills from its tail and has three capes on his shoulders each of different colour." "He too displays on the ground and strips the leaves from saplings so he can dance in a pool of light." "Other birds of paradise display up in the branches." "The males don't acquire these plumes until they're several years old." "And they moult themevery year at the end of the breeding season." "So for much of the time, they look very like their drab females." "When they're dressed for the dance, they spend a lot of time grooming and cleaning themselves, lavishing as much care on their display feathers as they do on those utilitarian ones on which they depend for flight." "The females visit the display trees to select their partners." "But the males display whether they're there or not." "Each species, this is the lesser bird, has its own particular dance, its own characteristic way of showing off its finery to the best advantage." "The Emperor of Germany's bird begins with a fluffing up of the plumes beneath his wings,but has developed a most surprising climax to his performance." "Count Raggi's bird throws his plumes over his back in a quivering fountain of red." "But to me, the most remarkable and thrilling display of all is that of the bluebird." "And as he quivers and trembles, he sings as extraordinary and un-birdlike a song as comes from the throat of any bird." "(PULSING CALL)" "And these are some of the largest feathers in the world, and among the most spectacular." "The peacock's feathers." "They're still something of a mystery." "Darwin confessed that he was baffled by the sheer perfection of such feathers as these." "Were they really developed just to enable the peacock to compete in splendour?" "Or to impress the peahen?" "There are lot of people who think we have some way to go before we know the full answer to questions like those." "And this is one characteristic of the reptiles that birds never abandoned." "Laying eggs in nests." "Every other vertebrate group has some species that retain the eggs in the body and give birth to live young." "Some fish do it, some amphibians, some reptiles, and, of course, all mammals." "But there's not a single bird that does it." "The reason is pretty obvious." "It would be a severe handicap for a bird to fly around with the weight of this in its body, let alone a weight of a whole clutch, for as long as it takes for it to hatch." "Much better to lay it in a nest as soon as it forms." "But that, of course, makes the eggs very vulnerable." "And birds go to a lot of trouble to protect their eggs and their nests." "The peahen makes a straightforward nest in a secluded place in the undergrowth and she forgoes the attention-catching feathers of her mate so it she well camouflaged." "Several waterbirds, including the giant coot in Chile, lay their eggs on floating islands of vegetation, well beyond the reach of most robbers." "Other birds, these are oropendulas from South America, achieve inaccessibility by weaving bottle-shaped nests on branches." "On the pampas of South America, the oven bird builds a nest of mud." "It's shaped like a local oven, and when it's finished, it will have a tiny entrance hole which effectively foil most intruders." "Long-tailed tits weave a domed nest of cobwebs and moss, fill the inside with carefully collected downy feathers, and camouflage the outside with lichen." "The sparrow is one of the untidiest of builders." "Which will make use of any sticks around, including those being used by others for their nests." "In Iceland, there are great colonies of Arctic terns." "Shores where they nest provide very little building material and no cover whatsoever." "So they largely dispense with nests and do ther best deflect intruders by diving at them." "The safety of their eggs depends largely on their camouflaged shells." "Inside the eggs, the developing chicks, like their parents, have warm blood, and if they get chilled, they die." "The eider duck, which also breeds in Iceland, develops special downy feathers on its breast and with them builds one of the warmest of all nests." "Man himself has yet to devise anything more luxuriously warming than eider-down." "The colour of birds' eggs varies hugely." "And so does their size." "This is the smallest of all, laid by a hummingbird and no bigger than a pea, and this is the biggest." "It's probably the largest egg that it's possible to have." "Because obviously the shell has to be pretty thick to hold two gallons of liquid." "If it were any bigger, it might have to be so thick the young chick inside would be unable to hammer its way out." "This egg was found here in these thorn forests of southern Madagascar, and it was laid by a giant, flightless bird, one of the biggest to have existed, rather like the ostrich, standing about ten feet tall." "It was called the elephant bird, or aepyornis, and it seems that it was alive up to about 200 or 300 years ago." "But now, alas, it's certainly extinct." "Parent birds have to labour hard, keeping their eggs warm in cold climates, and in warm ones, protecting them from the sun so that they don't overheat." "And when the eggs hatch, they must collect food to supply their growing and perpetually hungry young." "Soon, these young storks will fly." "But where exactly will they go?" "To find out, stork chicks all over Europe have been ringed." "The rings are light and of aluminium and carry an address, so that anyone finding the bird will know where it was hatched and reared." "The young storks flap their wings, exercising the muscles that will have to sustain them in the air, while their parents continue to collect daily supplies of frogs and fish." "And then, after about 60 days, both young and parents depart." "The chicks miraculously having most of the skills of flying the very first time they launch into the air." "Some surprising results have come from ringing storks in this town in" "Southern Germany." "Many of the birds make their way to Africa, going east around the Mediterranean by way of Istanbul." "But the town lies on a fork in the migration route, and others go west across the Straits of Gibraltar." "And as they head south, they become more and more concentrated." "These immense continental journeys make great demands on a bird's strength." "Many rely on the upward thermal currents produced when the sun heats the land." "For if you can get high, you can glide effortlessly for great distances." "Thermals don't occur over the sea, so the migrants gain as much height as they possibly can before embarking on a crossing of the Mediterranean." "Near both Gibraltar and Istanbul, they soar round and round in the upcurrents, climbing higher and higher." "Those that arrive at the coast in the evening roost, for after the sun has gone down, there are no more thermals." "It's better to wait until morning." "So the Straits of Gibraltar each spring and autumn are visited by many thousands of bird travellers on their way to or from Africa." "The nearby mountains and the rock itself, warming in the Mediterranean sun, produce particularly strong upcurrents of air, and Africa lies only a few kilometres away across the strait." "A kestrel, taking a rest on its long journey." "Honey buzzards from much of Europe congregate here and share the thermals with the storks." "These great invasions of tourists often infuriate the local residents." "Sometimes, on dull days, the short- toed eagles can't get the lift they need for launching off to Africa and fly around Gibraltar harbour." "The local gulls don't care for this kind of intrusion and mob them." "Sometimes even drive them down into the water from which they can't take off again." "Just another hazard in the risky business of migration." "A black kite on its way back to Africa after breeding in Europe." "September in Gibraltar is a marvellous place for the birdwatcher as travellers congregate at this international crossroads of migration routes." "One of the best places to watch is from the very top of the rock itself." "It's coming to the end of the day and it's been a good one for the migrants." "Parties of big birds, 30, 40, 50-strong, have been passing the rock and gathering to get one last lift from a thermal in Europe so they can gain altitude and glide across the straits to Africa, 12 miles away." "But how did they find their way here?" "Well' Some undoubtedly used geographical landmarks." "They come along the coast." "Others follow prominent river valleys." "But that can't be all there is to it, because young birds that have never made the journey can manage to do so by themselves." "So they must have some kind of inherited map in their minds." "Other birds manage to use the sun in some way because they can cross large expanses of sea and even featureless land." "But the sun has one major drawback as a navigational aid." "It moves, so if you want to find your way by it, you have to know what the time is." "So those birds, presumably, must also have a clock in their minds." "But in the evening, of course, the sun goes down, it gets dark, and you may no longer be able to see geographical landmarks." "What happens then?" "The answer can be found here in the air traffic control tower at the rock." "Gibraltar is of great strategic importance in the defence of Western Europe and close watch is kept by radar of all aircraft movements around it." "But radar can show up flocks of birds just as it can show up aircraft." "And in the autumn and spring, the information that can come from these screens about what goes on in the skies at night is spectacular indeed." "A few hours of an autumn nigh can be condensed into a few seconds." "The numbers of birds crossing the straits of Gibraltar into Africa can be estimated from the mass of black dots moving south-west." "On this night, up to 200,000 birds at one time are represented on the screen." "It's estimated that 5,000 million cross the whole Mediterranean each autumn." "How do they find their way?" "Well, some birds seem to be able to fly by the stars." "Because if you release them in a planetarium where artificial stars have been twisted around, they fly by way of those." "Others birds apparently are sensitive to electromagnetic waves." "So it appears that a bird not only has to have a map of the land and a star chart and a clock, but also a compass in its mind." "But the fact remains, there's still a very great deal we don't know about bird navigation." "Gibraltar is only a halfway stage for most migrants." "Arctic terns hatched in Iceland in July are here in September, but they still have 10,000km to go before they reach their destination." "Shearwaters move in a different direction, migrating east and west between the Mediterranean and the Atlantic." "They're great travellers." "One returned to its nest in Wales, crossing the Atlantic in 12 days." "This Arctic tern has now reached the southern tip of South America." "Having left the Arctic at the end of summer, when the sun never set, it's flying to the Antarctic summer, so it sees more daylight than any other living creature." "The African plains are the target for the storks." "By the end of September, they're feeding among game just as they did among dairy cows only a few weeks earlier." "So flight, the birds' supreme achievement, has carried them not only to all parts of the world, but has made them into the greatest of all animal travellers." "And yet, most surprisingly, some species have abandoned it." "There is no doubt that the ostrich's ancestors could fly." "Its body still retains adaptations for flight." "A beak instead of heavy teeth and jaws, and feathers on its wings that sprout in patterns needed for flight." "But now they're used only for display." "Since the feathers need no longer support the bird in the air, the hooks on the filaments have disappeared and the feathers have a soft fluffiness that is found to be alluring by other creatures as well as female ostriches." "But why should the ancestral ostrich have given up flight?" "Well, flying is a very demanding business." "If there are no ferocious predators to drive birds into the air, it's much easier option to remain on the ground." "That often happens today on islands, and it happened once to the ancestor ostriches." "Ostriches belong to one of the most ancient of the bird families." "When they first appeared, about 50 million years ago, the dinosaurs and other giant reptiles had only recently vanished, and the position of ruler of the world was vacant." "It seems that birds like that made a bid for it." "There was one great flightless bird in North America that had a huge, murderous bill, that looked as though it could kill any animal that was around at that time." "And even looking at these ostriches, it's not difficult to imagine how dangerous they might be if they suddenly acquired a taste for red meat." "They could certainly outrun me, and one kick from those legs could knock me over and rip me open." "But that bid for supremacy by the birds failed." "There was another, unobtrusive, little creature around at the time that also had warm blood." "But it was descended from a different group of reptiles and the birds, and it insulated its body not with feathers but with fur." "That was the creature whose descendants were to inherit the earth." "That was the first mammal."