Wednesday, September 5, 2007

The scene: a traffic light crossing

on a university campus in Japan. Carrion crows and humans line up patiently, waiting for the traffic to halt.

When the lights change, the birds hop in front of the cars and place walnuts, which they picked from the adjoining trees, on the road. After the lights turn green again, the birds fly away and vehicles drive over the nuts, cracking them open. Finally, when it’s time to cross again, the crows join the pedestrians and pick up their meal.

If the cars miss the nuts, the birds sometimes hop back and put them somewhere else on the road. Or they sit on electricity wires and drop them in front of vehicles.

Biologists already knew the corvid family–it includes crows, ravens, rooks, magpies and jackdaws–to be among the smartest of all birds. But this remarkable piece of behavior–it features in the final program of “Life of Birds”–would seem to be a particularly acute demonstration of bird intelligence.

The crows in Japan have only been cracking nuts this way since about 1990. They have since been seen doing it in California. Researchers believe they probably noticed cars driving over nuts fallen from a walnut tree overhanging a road. The crows already knew about dropping clams from a height on the seashore to break them open, but found this did not work for walnuts because of their soft green outer shell.

Other birds do this, although not with quite the same precision. In the Dardia Mountains of Greece, eagles can be seen carrying tortoises up to a great height and dropping them on to rocks below. The hapless Aeschylus (525-456 BC), a father of Greek tragic drama, is said to have met his end by this means.

A seer predicted he would die when a house fell on him, so the wary scribe departed for the hillsides, well away from any dwellings, where he believed he was safe. He wasn’t. An eagle is said to have mistaken Aeschylus’ bald pate for a stone, and dropped the creature in its “house” onto it.

Scientists have argued for decades over whether wild creatures, including birds, show genuine intelligence.

Some still consider the human mind to be unique, with animals capable of only the simplest mental processes. But a new generation of scientists believe that creatures, including birds, can solve problems by insight and even learn by example, as human children do. Birds can even talk in a meaningful way.

Some birds show quite astonishing powers of recall. The Clarke’s nutcracker, a type of North American crow, may have the animal world's keenest memory. It collects up to 30,000 pine seeds over three weeks in November, then carefully buries them for safe keeping across over an area of 200 square miles. Over the next eight months, it succeeds in retrieving over 90 percent of them, even when they are covered in feet of snow.

A Japanese carrion crow examines the fruit of its labors
On the Pacific island of New Caledonia, the crows demonstrate a tool-making, and tool using, capability comparable to Palaeolithic man’s. Dr Gavin Hunt, a New Zealand biologist, spent three years observing the birds. He found that they used two different forms of hooked “tool” to pull grubs from deep within tree trunks.

Other birds and some primates have been seen to use objects to forage. But what is unusual here is that the crows also make their own tools. Using their beaks as scissors and snippers, they fashion hooks from twigs, and make barbed, serrated rakes or combs from stiff leathery leaves. And they don’t throw the tools away after one use–they carry them from one foraging place to another.

Scientists are still debating what this behavior–shown in program three–means. Man’s use of tools is considered a prime indication of his intelligence. Is this a skill acquired by chance? Did the crows acquire tool making skills by trial and error rather than planning? Or, in its ability to adapt and exploit an enormous range of resources and habitats, is the crow closer to humans than any other creature?

Dr Hunt, then of Massey University in New Zealand, said this of his research: “There are many intriguing questions that remain to be answered about crows’ tool behavior. Most important would be whether or not they mostly learn or genetically inherit the know-how to make and use tools. Without knowing that it is difficult to say anything about their intelligence, although one could guess that these crows have the capability to be as clever as crows in general.”

The Caledonian Crow uses a twig as a tool to extract grubs
The woodpecker finch, a bird of the Galapagos, is another consummate toolmaker. It will snap off a twig, trim it to size and use it to pry insects out of bark. In captivity, a cactus finch learnt how to do this by watching the woodpecker finch from its cage. The teacher helped the pupil by passing a ready-made spine across for the cactus finch to use.

Sometimes a bird species’ very survival depends on its ability to learn fast. Birds need to recognize a cuckoo egg dumped in their own nest and either throw out the strange egg or desert the nest to start afresh. In Japan, the common cuckoo recently switched to a new, unsuspecting host on which to dump its eggs, the azure-winged magpie. The emerging cuckoo chicks ejected their foster siblings, and the magpie population dropped dramatically.

Ten years on, the magpies started to fight back. They learnt to detect the “foreign” eggs. Within a few years, there was a four-fold increase in its rejection of cuckoo eggs. The speed with which the magpie changed its behavior has astounded biologists.

The Galapogos Finch also uses a twig to extract a meal
Another sign of intelligence, thought to be absent in most non-human animals, is the ability to engage in complex, meaningful communication. The work of Professor Irene Pepperberg of the University of Arizona, Tucson, has now shown the general perception of parrots as mindless mimics to be incorrect.

The captive African grey parrot Alex is one of a number of parrots and macaws now believed to have the intelligence and emotional make-up of a 3 to 4 year old child. Under the tutelage of Professor Pepperberg, he acquired a vocabulary of over 100 words. He could say the words for colors and shapes and, apparently, use them meaningfully. He has learned the labels for more than 35 different objects; he knows when to use “no,” and phrases such as “come here”, “I want X,” and “Wanna go Y.”

A bird’s ability to understand, or speak, another bird’s language can be very valuable. New Zealand saddlebacks, starling-like birds, occupy the same territory for years. They have distinct song “dialects” passed on through the generations.

New territory vacancies are hard to find, so young males are always on the look-out for new widows into whose territory they can move. While they wander around the forest, they learn the different dialect songs, just as we might learn a language or develop a regional dialect.

As soon as a territory-owning male dies, a new young male may move in to take over within 10 minutes. He will immediately start singing the dialect of the territory he is in.

Intelligence–if this is what scientists agree these birds possess–is not limited to the birds we always thought of as “bright.” In recent experiments at Cardiff University in Britain, a pigeon identified subtle differences between abstract designs that even art students did not notice. It could even tell that a Picasso was not the same as a Monet. The experiment seems to show that pigeons can hold concepts, or ideas, in their heads. The visual concept for the pigeon is Picasso’s painting style.

Some birds seem to indulge in “intelligent” play. The kea, a New Zealand parrot, has been filmed ripping (inedible) windscreen wipers off cars. Young keas, in a neat variation of ringing the doorbell and running away, are known to drop rocks on roofs to make people run outside.

Jack the jackdaw was raised by wildlife film producer John Downer. As soon as Jack was mature, he was released into the wild. However, he couldn’t stay away. “One thing he is totally fascinated by is telephones,” said Downer. “He knows how to hit the loudspeaker button and preset dial button. Once we came into the office to find him squawking down the telephone to the local travel agent.”

Jack also likes to fly down onto the mirror of the production car when he sees somebody going out. “He turns into the wind, gets his head down and surfs on the air current until we reach about 30 mph when he gives up.

“Like all jackdaws, Jack shows great versatility and intelligence. Because he has to exploit a wide range of foods, he is investigating things all the time.”

However, scientists believe it is not physical need that drives creatures to become smarter, but social necessity. The complexities of living together require a higher level of intelligence. Corvids and parrots, along with dolphins, chimps, and humans are all highly social–and smart–animals.

Some ravens certainly apply their intelligence for the good of the flock. In North America, they contact other ravens to tell them the location of a carcass. Ravens are specialized feeders on the carcasses of large mammals such as moose during the harsh winter months of North America. The birds roost together at night on a tree, arriving noisily from all directions shortly before sunset. The next morning, all the birds leave the roost as highly synchronized groups at dawn, giving a few noisy caws, followed by honking.

They may all be flying off in the direction taken by a bird, which had discovered a carcass the previous day. This bird leads the others to his food store, apparently sharing his prize finding with the rest of the flock.

Ravens share information about their findings of food carcasses because dead animals are patchily distributed and hard to find. Many eyes have a better chance of finding a carcass, and once one has been located, the information is pooled.

Although the carcass now has to be shared between more individuals, the heavy snowfall and risk of mammal scavengers taking the kill mean that a single bird or a small group could not eat it all alone anyway. Some are even believed to solicit help with the carving, by tipping off other predators, such as wolves, about the meat so they will rip it open and make it more accessible to the ravens.

The African honeyguide lures badgers to bees nests, and feeds on the leftovers. To humans they offer their services as paid employees. They call and fly backwards and forward to draw local tribespeoples’ attention to the location of honeycombs, and are then rewarded with a share of the takings for their trouble.

Of course, the bird world has its share of “bird brains.” There are the birds that build three nests behind three holes under a flower pot, because they can't remember which is which, and birds that attack their own reflections. The Hawaiian goose is as innocent of danger as a baby crawling along the girder in an unfinished skyscraper. It would walk up to an introduced mongoose on Hawaii, and be attacked.

The level of intelligence among birds may vary. But no living bird is truly stupid. Each generation of birds that leaves the protection of its parents to become independent has the inborn genetic information that will help it to survive in the outside world and the skills that it has learned from its parents.

They would never have met the challenge of evolution without some degree of native cunning. It’s just that some have much more than others.

The kiwi is one of the rarest

and shiest birds in the world. It only comes out to feed by nights in remote parts of New Zealand. So how did the BBC manage to film it so candidly for "The Life of Birds?"

Series producer Mike Salisbury takes up the story. It proves the value of the assiduous "reccy" or reconnoitre trip, the many months spent in research before an inch of film was shot.

Mr Salisbury went to New Zealand determined to find a good location in which to film the unique bird. "After a month I had still not found anywhere. The kiwi is the national symbol, but even the Department of Conservation said it would be so hard to find we might have to film tame birds. I told them wherever possible our policy was to film birds in the wild, behaving naturally." Eventually Mr Salisbury met a man in a bar in Invercargill, on the southermost tip of New Zealand, who told him kiwis could be seen on Stewart Island off the south coast. He took the ferry, booked into the hotel and asked around. He was directed to local man Philip Smith who took him out that night in his boat, around a headland to a secluded beach.

"We crouched down on the sand and, just as the moon rose, out of the forest came two kiwis to feed on sand hoppers along the tide line. It was a magical moment. We wrote this scene into the script and returned the following year to film the perfect sequence with Sir David Attenborough." [It features in the last part of the first program.] They used the Starlight camera (so sensitive that, as the name suggests, it only needs starlight to operate).

"The Life of Birds" took three years to make at a cost of $15 million. Sir David Attenborough travelled 256,000 miles during filming - 10 times round the Earth. The production employed 48 cameramen and camerawomen, many of them battle-hardened veterans of overseas wildlife filming, working in 42 countries on five continents. They used up 200 miles of film on 300 bird subjects.

The kiwi filmed by starlight camera
They applied the latest techniques of ultra-slow motion filming, night vision cameras and tiny cameras that film inside nests, allied to plain old-fashioned field craft, to bring in footage of some of the world's rarest birds and examples of remarkable avian behaviour never filmed before. The few failures were greatly outnumbered by many spectacular filming successes.

The series is the logical follow-on to the BBC's Private Life of Plants. Mike Salisbury, a veteran producer in the unit, was appointed executive producer. He met with Sir David to decide the number of progams and a basic structural outline. Sir David then wrote a proposal, outlining the program themes. This document was accepted by the controllers at the BBC and co-producers PBS.

BBC Natural History Unit wildlife series like this follow the same painstaking development - with up to a year of planning before an inch of film is shot. The series is founded on an exhaustive world-wide research trawl to find the best answer to any question presenter and producers could put on birds, providing the best examples to illustrate any avian point they wanted to make.

Two researchers spent many months reading journals, scientific papers and books; they contacted behavioural scientists in universities, people in bird organisations and all the main naturalists conducting research on birds around the world. The Internet, too, became a powerful research tool during the making of this series.

A bird take a look at a grub (and possibly a micro camera)
The researchers' brief was to gather many good examples and stories on bird behaviour, preferably new ones that not been covered much, if at all. The final research document contained far more examples than could ever be included in the series. Many old assumptions about birds were junked. The researchers frequently came across interesting avian behaviour of which Sir David had never heard. Unexpected discoveries were made - for example about the unassuming British dunnock, which turns out to be a garden Lothario.

"In many meetings we kicked around what we liked and didn't like in the short-list of stories, themes and possible sequences," said Mr Salisbury. "Sir David would argue his case or accept a better example. Then the producers assembled, and we divided up the world into research areas - North America, South America, Africa, Australasia, the Far East.

Armed with these draft treatments, each producer was sent off to investigate his zone of the world. They tried to visit the scientists who had given them the fruits of their research and decide how to turn it into a film sequence. Years of work were, of necessity, pared down to a brief few minutes of TV in the series. Often the visit would tease out new ideas, and identify better film locations.

Only now would filming begin. "It is important to plan carefully," said Mr Salisbury "There is the danger that if we started too soon, our film sequences would not fit in with the overall plan. We had to know the context: filming had to be relevent to the story we are trying to illustrate."

The series hired a top team of seven cameramen - famous names in wildlife filming like Barrie Britton, Andrew Anderson and Mike Potts; and one one women, Justine Evans.

They used the latest technology. But this was not a series for which radical new equipment was specifically devloped. Mr Salisbury explained: "We decided that, unlike Private of Plants, where we spent a lot of the budget developing new technologies to film plants, for this series we would use much of our budget on keeping our camerpeople in the field for much longer that they would normally stay even for an important wildlife documentary. We wanted them to be out there for as long as it took, employing good old fashioned field craft to film their subjects.

Professor Davies, studying the lifestyle of the dunnock
"We also decided not to use any trickery: no filming against false blue backgrounds, for example. Nor did we want to attach miniature cameras to birds. We wanted to make the sequences as natural as possible, filming as much as we could in the wild with real wild birds."

However there were a few occasions where they did use habituated birds, when they wanted to show big close-up details of flight, where it was an advantage to have a camera directly alongside a flying bird.

To achieve this they used the technique of "imprinting", which several producers at Bristol have perfected. So consultant Conrad Maufe became a duck "mother" (the results are in programs 2 and 5), personally caring for birds from the moment they left the egg. In the absence of a real mother, the ducks fastened on Mr Morfe as their surrogate "mother."

Once they had learnt to fly they would follow him anywhere, when he was riding a bicycle or even driving a car. In one sequence, filmed on a dam in North Wales, Mr Maufe drove a car along the water's edge, with cameraman Mike Potts sitting next to him training a camera on a drake from Mr Maufe's "family" flying alongside, a few feet away.

Producer Nigel Marven wanted, in the same unbroken sequence, to show the drake flying close to the camera, then banking over to Sir David who would be sitting in a boat in the lake introducing the program on water birds (program five). It went exactly as he had hoped. The drake did tear himself away from his "mother", breaking the bonds of imprinting, because he had seen his harem of female ducks sitting on the water around Sir David's boat. One lure turned out to be stronger than the other.

This imprinted mallard flys alongside the camera vehicle
Mr Salisbury cites some of the sequences of which he and the team are particularly proud. One was the filming of New Caledonian crows, which use tools to extract grubs from trees. "It had only just been discovered and had never been filmed. We used a micro-camera inside the tree to reveal more about the exact technique used by the crows than even the scientist who discovered it had known. People had told us we just couldn't film it."

Then there was the buff-breasted sandpiper in the Alaskan tundra. A PhD student had just discovered its extrordinary mating display, an usual dance by the male. But it only happened for four days each season, immediately after the first snow melt, which is very unpredictable. The crew were filming phalaropes in the region when the researcher alerted them to the arrival of the first sandpipers. They dropped everything and rushed over to film the sandpipers. If they hadn't done so immediately, they would have missed the action - that year only the first day was suitable for filming. The next day thick fog set in and stayed for the rest of the week.

"They had to make quick decision," said Mr Salisbury, "whether to leave what they were doing and go to film the bird, a day's journey away." They decided to go. In the end it made an important four minute sequence (see it in in program 7). In caves in Venezuela, Justine Evans used low light cameras to film oil birds, "illuminating" the scene with infra red light which birds cannot see. Sir David was left in the pitch dark to make his commentary.

One sequence amply illustrates one of the series' great values - attention to detail. Peter Bassett and Andrew Anderson were determind to film a dawn chorus in a depth that had never been achieved before. They made sure every shot was genuinely at dawn, back lit so the bird's breath can be seen - an indication of early morning chill. Microphones were fixed to the posts where the birds perched to record them as they sang: it was not, as sometimes happens, added afterwards.

The New Caledonian crow footage broke new ground
The same applied to the episode with the lyre bird, the superb mimic able to copy the sound of a camera's motor drive and many other details. The cameraman insisted on filming with synchronised sound because he thought viewers would not otherwise believe it was happening.

The film makers suffered frequent discomfort, sometimes of an amusing nature. Producer Peter Bassett was bombed in the face with droppings by angry fieldfares that attacked him to defend their nests. One scored a direct hit on his glasses.

Cameraman Barrie Britton spent a cramped week lying on the ground in a hide in Professor Nick Davies's garden in Cambridgeshire to film the hitherto unsuspected bigamy of the unassuming donnock.

One film crew had to dress up in costumes reminiscent of the Ku Klux Klan to film endangered whooping cranes in the USA. They were also not allowed to talk to each other, but had to hoot just as cranes do.

Sometimes things did go wrong. In Alaska a scientist had just discovered that the spectacled eider ducks of the Arctic Circle wintered at a rent in the sea ice way out from shore. Thousands of birds keep the water ice-free with their body warmth, feeding on molluscs 200 feet down. A crew tried to film them from a helicopter, but it was so cold the film kept breaking.

The lyre bird
Cameraman Nick Gordon was on in a tree platform 75 feet up in the Amazon rainforest to film calfbirds displaying (never filmed before), when his tree was struck by lightning. And while trying to film Jamaican streamertail hummingbirds, a crew were severely bitten by swarms of tiny cattle ticks that infested their whole bodies.

The most logistically difficult trip was to the Himalayas, to film the mating behaviour of the Nepalese honeyguide. 40 porters carried the crew's gear, provisions and combs of dripping honey to attract the birds into an isolated valley. They found the birds, but mating never took place.

Returning from a trip to New Guinea a crew had their rare film of the McGregor's bird of paradise ruined by a powerful new airport security X-ray machine. It had been introduced, to detect explosives, without passengers being told. They were unable to return to reshoot the sequence because of an outbreak of tribal unrest.

It took two and a half years to complete filming. Sir David was kept extremely busy. The sequences where he speaks to camera on location and interacts with birds - for example where he "talks" to woodpeckers in Patagonia by tapping a tree - take a lot of time to set up.

"It is a lot more time consuming than if we used Sir David in a general location shot, then cut away to the birds. It's much more more difficult to get him in the same shots as the birds.

"We think a big feature in the success of the series is his terrific ability as a storyteller, to hit on a concept for each programme and work out a way to keep the viewer's attention, inviting the viewer to want to know more."

Birds arrived comparatively late

on Planet Earth. First came insects, in the unimaginably distant past. For over 100 million years or more they ruled the skies. But these were mere pioneers of the air. Think of them, in aviation terms, as the flimsy open-cockpit planes of the early 20th Century.

Then, several hundred million years ago, huge and often terrifying new life forms, Pterosaurs, or flying dinosaurs, took the ascendancy. These massive creatures had wings of skin, stretched between one enormously elongated finger and their flanks. Around 150 million years ago they were joined by - or, as many scientists say, they began to turn into - a much more aerodynamic, feathered creature. The bird was born.

And so the flimsy biplane ceded aerial mastery to nature's many equivalents of the Boeing 767, Concorde, the B52 bomber, the stealth fighter. A huge variety of ancient bird types have come and gone and evolved to give us the 9000 different species we know today.

Many scientists are convinced that birds evolved from the dinosaurs. Numerous finds in recent years have seemed to support the hypothesis that birds descended from two-legged, running dinosaurs called theropods.

Pterosaurs were among the first vertebrates in the air
This theory was born with the discovery of a 150-million-year-old fossilised creature in a swamp in Germany in the 1860s. Archaeopteryx was possibly the most controversial prehistoric remain ever dug up. It is the oldest known bird fossil. Most biologists accept it as conclusive proof that dinosaurs sired birds.

Archaeopteryx had three toes armed with claws and long, strong legs. Clearly it walked and perched like a bird. Its head had the reptilian feature of jaw bones. Its spine was extended into a bony tail - just like a reptile's. On both sides of the tail bones, clearly visible, were the clinching characteristics of birds - feathers.

But not all scientists agree with the birds-from-dinosaurs link. Alan Feduccia, professor of biology at the University of North Carolina, is a noteable doubter.

He contends that Archaeopteryx wasn't the ancestor of all birds, but just another of nature's many experiments. He argues that a huge evolution of birds had been going on before[italics] Archaeopteryx, and that they evolved from four-legged forest reptiles.

In 1996 Feduccia investigated an intriguing bird that lived about 135 million years ago, just after Archaeopteryx. The bird, Liaoningornis, did not look like a dinosaur bird at all. It had a breastbone similar to modern birds, with massive flight muscles that enabled longer flights.

It was found alongside fossils of ancient birds not unlike Archaeopteryx. Feduccia believes that birds were very widespread by that date, occupying a variety of habitats. He believes most of them died out with the dinosaurs, about 65 million years ago.

The ancestors of all today's birds evolved later, he says, between 65 and 53 million years ago, independently of the dinosaurs. This is the "big bang theory" of birds. Feduccia and his fellow sceptics - it must be stressed they are in the minority - regard any similarity between birds and dinosaurs as an example of convergent evolution, by which two independent groups grow to look alike.

However the dinosuar-to-birds theory took another startling turn recently with the discovery of two species of feathered dinosaurs in China, dating from between 145 million and 125 million years ago.

"This is the most important dinosaur discovery of this century," said Philip J. Currie of the Royal Tyrrell Museum of Paleontology in Drumheller, Alberta. "The credibility of the dinosaur-to-birds theory takes a gigantic leap ahead with these specimens."

While scientists continue to debate exactly where birds came from, nobody denies that their subsequent success in colonising the planet has been immense.

Since the catastrophe that wiped out the dinosaurs - now commonly believed to have been a huge meteor - birds have taken total command of the skies. For a time, when the early mammals were still quite small, birds effectively ruled the planet. Huge flightless "terror-birds" stalked the land. Mighty vultures cruised the skies. One had a wingspan of over twenty feet - bigger even that that of the Andean Condor, and probably the biggest flying bird that has ever existed.

The power of flight gave birds the edge over most other creatures. They could travel futher and wider in search of food, and live where no other creature could go. Millions of years of evolution have adapted each bird species to fit into its own little niche and pre-programmed it to feed, to migrate, to nest and breed in its own particular place and manner.

Birds have adapted so well to the demands of and trials set by our planet that Sir David Attenborough believes they may be the most successful creatures on earth, more successful even than insects.

Archaeop- teryx glides in for a meal
At the southern extremity of the world lives the Emperor Penguin, better adapted to the cold than any other animal on earth. Short feathers made up of tiny filaments that trap the air in a continuous layer all around the body enable the adults and chicks to survive some of the coldest conditions on Earth, the Antarctic ice-cap in winter.

The champion of the Arctic, in the cold north, is the ivory gull. This beautiful snow-white gull breeds further north than any other bird, and it perfectly adapted to the conditions which defeat most other life forms. It lives here all year-round, even in the dreary winter dark.

The bar-headed goose breeds in one of the most desolate places on earth - high up on the Tibetan plateau, deep within the heart of the vast Asian continent.

Equally desolate, but much hotter is the vast barren landscape of the Atacama Desert in South America, with not a green leaf in sight. The savage, searing sun heats the grey sand up to temperatures as high as 50C. In this dreadful desert grey gulls live untroubled by predators. But they have to fly hundreds of miles to find food.

There are many other examples of birds living on the edge. The oilbird lives in the total blackness of Venezuelan caves. The rufous hummingbird survives and breed at altitudes of 9000ft and at temperatures well below freezing by making a nest of the highest insulate qualities, a network of lichen and spiders web, as good as the finest down.

Emperor Penguin males shuffle along with the eggs they are caring for
The gouldian finch, one of world's most beautiful birds, requires fire for its food. It feeds mainly on the seeds of one plant - speargrass. It is only after fires - started by accident or by man - have cleared the undergrowth that the birds can reach the seeds on the ground. Another bird that lives on the elemental edge is the Temmincks courser in Africa. It seeks grassland that has just been razed by fire for its nesting habitat. Yet there are practical benefits in such a forbidding terrain. A flush of insects follows the inferno; and the open vistas enable it to see predators.

There have been many extinctions as birds edged up evolutionary blind alleys, and as periodic ice ages swept up and down the latitudes. In one prolonged period of cold about 3 million years ago, climate changes may have caused the extinction of a quarter of the existing bird species.

But, armed with the beak, one of the most versatile of all nature's feeding implements, birds have colonized the world.

It's as if humans had developed a hundred thousand different versions of the knife and fork.

The Gouldian Finch
High in the New Zealand Alps lives a bird that finds food with a unique beak. In shallow, gravelly streams the wrybill probes for larvae under heavy boulders it couldn't hope to shift. It has the only beak in the entire bird world that's bent to one side (the right).

Today the main threat posed to birds comes from man, his destructive tendencies and his manipulation of the environment. The life of birds has changed enormously since man spread widely around the planet, and began to develop and despoil it. Man is the primary force threatening the natural world. Habitat destruction, hunting, introduction of alien species and pollution combine to threaten almost 1000 species of birds world-wide.

Perhaps the best known bird extinction is the passenger pigeon, a North American species. It may once have been the commonest bird that has ever lived on earth. There was a population of an estimated two billion birds in colonial days, when huge overflying flocks would darkened the sky. But even these phenomenal numbers could not guarantee the bird's existence. European colonists cut down the beech forests that provided food for the pigeons, and slaughtered the birds for food. The last wild pigeon was shot by a boy in 1900; Martha, the last captive bird, died in Cincinnati Zoo in 1914.

Birds living on small islands are highly vulnerable to extinction. Many have become flightless in the absence of natural predators, and when man arrived, with rats, cats and other animals, the birds stand little chance. Over 90% of birds that have become extinct during historical times lived on islands.

The wrybill has a unique curved beak
The dodo is the tragic symbol of bird extermination. This large, flightless, turkey-sized pigeon lived on the tropical island of Mauritius. A fruit-eater, it had little reason to move fast or fly. It was easy prey for man the hunter.

The sailor Volquard Iversen, shipwrecked on Mauritius for 5 days in 1662, gave the last eye witness account. He wrote: "They were larger than geese but not able to fly. Instead of wings they had small flaps, but they could run very fast." Not fast enough, though, for human hunters, Only fossils and a few preserved specimens remain to remind us of this tragic species.

On the islands of New Zealand you can still glimpse what the world would have been like if birds had won the battle with the early mammals and now ruled the earth. These islands, with no endemic mammals, and isolated for so long from man, became a true paradise for birds, many of them flightless.

The dodo
There were twelve species of moas, including the tallest bird that has ever been known, The first human settlers on these islands saw these giants alive, then proceeded to slaughter them. Within 200-300 years most of the moas' habitat was destroyed, and all the moas were hunted to extinction in one of the greatest mass extinctions of birds in man's history.

But many extraordinary birds still live only in New Zealand, including the strange, nocturnal kiwi, and the heaviest parrot in the world, the flightless kakapo, which is itself on the brink of extinction.

The other effect man is having on birds is the phenoenom of climate change, caused by global warming, believed to be mainly a result of the burning of fossil fuels. One of the likeliest victims is the Bermuda Petrel, surely doomed if the earth gets much warmer. The bird nests in burrows on the side of the cliffs just above the sea-line. But with increasing warming of the earth and the danger of the sea-level rising, these petrels risk being washed out of their burrows.

The Bermuda Petrel's history has been one of continuous disasters. In the early 1600s, the birds were hunted and eaten in their thousands by the first sailors and settlers that arrived on Bermuda. The petrels only come to land at night, and the sailors called them "cahow" after their fearsome call. Within 20 years of the islands being settled, the birds were thought to be extinct, and for 300 years they remained a folk memory. In 1951 about 18 pairs of birds were re-discovered nesting in shallow burrows and rock crevices on tiny offshore islands.

Man makes a damaging impact on the natural environment of birds through farming, forestry and building works. There are many casualties: in Britain ornithologists have noted the decline of many once-common birds like the song thrush and the skylark, because of intensivive farming regimes. The British government now publishes an annual index containing certain key bird species; it has accepted the tenet that a fall in bird numbers damages the citizen's "quality of life."

Sometimes birds destroy their own habitat. La Perouse Bay on the Hudson Bay in the Canadian Arctic is a traditional breeding ground for the lesser snow goose.

After reserves were created to protect the birds, the population grew to such an extent that the birds actually ate themselves out of their own food. La Perouse Bay today is a saline desert - the geese have eaten and destroyed all the natural grasses that used to grow here. But such self destruction is the exception.

The birds that survive best tend be those most tolerant of man, or most able to take advantage of him. Birds like the waxwing, which have become a major problem for blueberry and strawberry growers in Florida and other states. Flocks of 500-1000 tiny birds can wipe out a whole blueberry crop within a few days.

Some birds, perversely, actually benefit from the pollution from intensive farming. The concentrated fertilisers farmers apply to fields may be good for the crops, but when they are washed out by the rain they contaminate streams and rivers. Rich nutrients cause some aquatic plants and invertebrates to flourish at the expense of the delicate balance of life in the waters.

This is bad for many birds, but not the ruddy duck, a small diving duck of North America. It feeds on the small aquatic Chironomid larvae in lake and river sediment. The larvae thrive in agricultural run-off. Ruddy duck feed on the burgeoning larvae and are also doing well.

The densely crowded and noisy cityscape would seem to be a highly inhospitable place for birds, unlike anything nature has produced. And yet there are birds which survive and prosper in the city. These are the generalists - able to eat anything and nest anywhere.

Black vultures in Sao Paulo city are never more than a flap and a glide from all the fetid rubbish they can eat. These urban scavengers nest on window ledges and roofs of tall skyscrapers. Some spend hours each day basking in front of warm exhausts from air-conditioner units.

Moa foraging for food
In Kampala, Uganda, marabou storks are seen on the Sheraton Hotel. In parts of Africa the white stork now only nests on buildings.

In downtown Manhattan, peregrine falcons can be seen hawking down the "canyons" between buildings for small birds. In the black townships of South Africa, red-footed falcons roost in large numbers. They often select a large tree close to a source of light and pick off the many insects attracted to it.

In Trafalgar Square, London, in the middle of one of the world's largest cities, pigeons outnumber people. These unfussy feeders survive easily on the many scraps of food. The many city window ledges and concrete structures provide ample nesting sites, perfect substitutes for the cliff ledges that are their natural nesting places.

Many storks have adapted well to man
Birds also receive immeasurable assistance from the active caring of millions of people around the world. The food put out by ordinary homeowners benefits countless birds. Many Americans and Canadians feed hummingbirds. The profusion of artificial feeders seems to changing the migration paths of the some species. In Arizona thousands of hummingbirds come each day to one particular garden feeder.

Many people put up gourds or more expensive bird houses for the purple martin. Now the bird prefers the articifial structures to its traditional home. There are many more examples throughout the world. In Britain the passion by householders for feeding birds in harsh weather is known to support a number of declining species. The main bird British body, the RSPB, has 1 million members.

Promoting alternative methods of food production and income for local people in underdeveloped countries is crucial to successfully protecting wild birds' habitats; this is the approach that is increasingly being taken by conservation projects around the world. Local people are being encouraged to look on birds and other wild creatures as economic assets, for example making their area more attractive to tourists.

In a Cameroon village, elders struck a deal with western conservationists to save the forest containing their scred bird, the Bannerman's turaco. Near Melbourne in Australia tourists pay big money to watch the nightly parade of the little penguins, and fund their conservation.

There are many examples of committed conservation projects which have saved birds otherwise doomed to extinction. Schemes to rescue the Gurney's pitta, the western tragopan and Bannermann's turaco are just a few of the many integrated conservation projects currently underway.

Birdhouses have become the favored homes of many birds
The programme to save the black robin on the Chatham Islands off the coast of New Zealand in 1976 is one of most famous conservation success stories of all.

There were just seven birds left on all the islands, and only one was a female. Scientists removed the female's eggs as soon as they were laid, so inducing her to lay more than one clutch per season.

The eggs were placed into the tiny nests of surrogate parents (warblers and tomtits). The robins were then raised as the tomtits' own chicks and fed up to, and past, fledging. Today there are more than 200 pairs of robins on the Chatham Islands. The idea of using surrogate parents to incubate eggs has been widely copied.

A black robin
In North America a remarkable breeding programme has brought the whooping crane back from the brink of extinction, from just 16 pairs to over 300. They are fed with a crane-shaped glove puppet to stop them becoming humanised.

But it's not enough to raise the cranes by hand. Somehow they must find the way to their traditional wintering grounds. Idaho farmer and whooping crane breeder Kent Clegg knows what to do. When the time is right, he leads them south to New Mexico. Behind his microlight.

So where are birds going? More extinctions are certain, as man drives on to conquer the remotest parts of the globe, and populations grow and climate continues to change.

But other species birds will return to old habitats, often with man's help. One remarkable example is the red kite, a bird wiped out by Victorian hunters in England, and now thriving in a heavily populated area just 20 miles north of London where several pairs were reintroduced in the early 1990s. They fend for themselves, feeding on a ready supply of small mammals killed on the road.

And the shape of birds to come? That can only be guessed at, as birds continue to adapt to habitats and changing conditions. One thing is certain. Such a versatile creature will always be with us, and with our distant descendants.