Eyewitness II; #106; Bird

This is... Presentation of this program was made possible by the Corporation for Public Broadcasting and by annual financial support from viewers like you. (birds chirping) From this

simple and perfect shape emerges an animal of such variety and beauty. It has captured our imagination, inspired our reverence, and taught us the secret of flight. We've always yearned to be free as a bird, and our fascination with these princes of the skies is as ageless as humanity itself. From this protective shell, a chick prepares to hatch, continuing a cycle that has been evolving and repeating itself for millions of years. 200 million years ago there were birds. Insects were the only flying creatures. Then came the pterodactyl, a giant flying reptile with wings made of membranes. But membranes were easily torn and couldn't be repaired. During the heyday of the pterodactyl, evolution solved this problem with the feather.

feather, one of nature's greatest innovations. The first feathered creature that we know of, the first bird, was Archaeopteryx, which lived one hundred and fifty million years ago. It's reptile-like teeth and tail provide an evolutionary link between flying reptiles and the feather covered bodies of birds. From Archaeopteryx and its descendants came the 8,500 species of birds that currently populate the earth. A determined bird watcher setting out to see each and every species of bird would have to observe a new species every day for the next 23 years. There are now about 500 billion birds in the world. A single fertile cell surrounded by yolk soon divides and multiplies so that after only a few days the heartbeat is the discernable.

Halfway through development limbs begin to take shape. Before the chick can crack the egg it must turn itself and break the air sac. After filling its lungs with air for the first time, the chick may call to its mother, signaling to her to prepare for the onset of hatching. From the faintest chirp inside an egg to the-round-the clock song of a nightingale, the elaborate language of birds far surpasses that of humans. Poets would have us believe that a singing bird is proclaiming its happiness, but birdsong has more to do with proclaiming territory, like this bellbird, whose call can be heard up to two and a half miles away. Bird song is also used to attract a mate. The song of the male lyrebird is actually a medley of borrowed tunes. Eighty percent of its song is mimicry of other birds. The repertoire can even include barking dogs.

And with tail feathers shaped like a Greek lyre, it's not difficult to work out the origin of its musical name. Perhaps the most unmusical bird is the raven. The Norse god Odin is often depicted with a raven on each shoulder. It was believed these ravens flew around the world every day and reported to him what they had seen. The bird as gossip survives to this day in the phrase, "A little bird told me." As well as couriers of scandal, birds were also seen as omens. A pure white bird is so rare that seeing one was considered a portent of death. This may have had to do with the cry of the swan, so mournful, that for a long time

it was believed the swan sang as it died. The belief proved false, but we still refer to someone's final act as their swan song. (music) (music) (music) (music) How does this creature that has given flight to our imagination become airborne? How does a bird fly? Bone structure, metabolic rate, wing structure, and the unique design of the feather all play a part in the bird's ability to fly. The lighter the material, the easier it is to get off the ground.

A land animal's bone consists of a heavy honeycomb of tissue. A bird's bone is almost hollow and reinforced with lightweight struts, and less bone requires less muscle, very handy when it comes to defying gravity and performing takeoff, the most difficult stage of flight. And takeoff is the moment that separates the fliers from the walkers. (music) (music) (music) (music) With so little muscle, how can a bird be so active and not suffer from

exhaustion? Actually, some do. The Pheasant can only take off a few times before it becomes exhausted and incapable of flight. (music) Most birds, however, can sustain long periods of hyperactivity. The hummingbird feeds while beating its wings up to 80 times a second. But to sustain such levels of energy, birds must take in large amounts of food. To "eat like a bird" is actually to have a voracious appetite. A hatching chick consumes the egg's yolk, now a marble-sized sack of food attached to its belly. It provides the chick with energy to get through the most exhausting day of its life. Once fully grown, a small bird may consume its body weight in food every day. That's about 300 small insects. A larger

bird of prey consumes up to a third of its body weight per day, and the equivalent for the average human? 100 hamburgers would do it. With so many calories to burn it's no wonder birds have the highest body temperature of all warm blooded animals, and their blood hurtles around their bodies at rates that would kill a person. Ourl resting heart rate is about 60 beats per minute. A Robin's heart beats at 600 times a minute. It's this ability to deliver an immense amount of energy to the wing, combined with a lightness of design which allows a bird to lift off the ground and stay there. Like the swimmer through water, a bird pushes against the medium of air to fly. The wing is light, strong and extremely flexible, allowing the bird to work

against or with the air. Birds can sit on the wind, their wings held on the air currents, Or catch rising pockets of warm air called thermals, riding them like invisible escalators to tremendous heights. Just as birds push against the air to achieve flight, they push against the air to end it, using their wings like brakes. Even though human flying machines have conquered the basics of flying, birds possess one skill that our flying machines will never master: self-repair. (airplane sounds)

Because of the wear and tear of flight, any flying machine needs constant maintenance. A bird is no different. To pass inspection, a feather must provide a smooth streamlined surface for air to flow over, but breaks in a feather can occur between the hundreds of barbs attached to the shaft which are zipped together by hundreds of barbules. When a bird preens it is zipping up the gaps in its feathers. But keeping its feathers airworthy is just one task in preening. This stork is collecting oil from a preen gland and spreading it over its feathers. Oil acts as a waterproofing agent for water birds, turning them into waterproof vessels.

The droplets of water simply slide across the surface of the feathers like rainwater off a shingled roof, or water off a duck's back. (music) All ducklings can float within 24 hours of birth, but take two to three weeks to grow proper waterproof feathers. This duckling has broken through the shell using an egg tooth, a small projection on its beak, and has begun pushing itself out. For the ancient Egyptians the sight of a young bird breaking out of the shell helped explain the origins of the universe. One myth held that the God Nut took the mud of the Nile and made a cosmic egg from which the cosmos was hatched. Today the association of the egg as a course of new life persists in the Christian

celebration of Easter. The Easter egg is a symbol of Christ's tomb, from which he emerged at the resurrection. And it's no coincidence that Easter takes place in the spring, the time of renewal, the time in which migrating birds fly great distances to their place of renewal, breeding grounds. The king of the long haul is the the arctic tern. Each year these birds migrate from pole to pole. That's over eighty five hundred miles one way. After a nonstop flight lasting over two and a half months, they finally arrive at their breeding grounds in late April, only to set off again in July. In temperate climates, the arrival of spring and the spectacle of huge flocks of geese flying overhead are inseparable. In ancient cultures humans who knew nothing of migration and only saw geese leave

before winter and return in the spring believe that geese literally carried the spring with them. The belief gave rise to goose myths and ceremonies in ancient Greece and Japan, and gave the goose special powers in folklore because of its association with spring, fertility, and good fortune. In many cultures, even though the goose has been replaced by the turkey, the eating of a bird on holidays harkens back to these beliefs. Even the cuckoo, another spring arrival associated with the changing seasons, is still married to our concept of time. The penguin is identified with a very different season: winter. But the familiar image of these ice bound wobblers belies their true abilities. For penguins do their flying under water, and not just Arctic waters. Here in the warm waters of the Pacific islands, the Galapagos penguins fly through the sea

with extreme agility, using their flippers like wings. But there are birds that are truly flightless. The wings of an ostrich serve little purpose, for the ostrich is the world's heaviest bird. At two hundred and sixty pounds, it is permanently grounded. It's believed ostriches evolved at a time when food was so plentiful flight was unnecessary. And with the ability to run up to 40 miles per hour, making it the fastest two legged animal on earth, The ostrich stands a pretty good chance of leaving most predators in the dust. Until they are fully grown flightless birds need constant protection. With predators such as this Egyptian vulture lurking in the wings, it's no wonder that ostrich eggs have evolved a thick shell to protect them from hungry mouths. No beak could break through

this. But a stone can and so the Egyptian vulture has cracked the problem by learning to use a tool (stone on egg sound) This ability to conquer nature's defenses by using a tool earns the vulture a place among the most intelligent of birds. At the other end of the scale, looking wise is not being wise. The owl is actually one of the least intelligent birds, but it's ability to see in the dark makes it an emblem of clairvoyance in Mexico and the symbol of death in ancient Egyptian tombs. Neither psychic nor funerial, the owl is a creature with highly developed senses. An owl's eyes are especially adapted for night vision, packed with light sensitive rods. At the moment of attack the eyes actually close, and the owl relies on its

sensitive talons to zero in on the exact position of its target. It's not the wisdom of the owl but the tools of its trade that account for its success. Like human tools, a bird's beak performs a variety of tasks, but unlike humans they never lose them. The short sharp beaks of woodpeckers are used like drills to make nests for their young but are primarily used for boring for food. As form follows function, the shape of a bird's beak is determined by its diet. The fruit-eating macaw needs to supplement its diet with kaolin and uses its beak like a pick on rock. The greatest variety of beaks is found among water birds:

tweezers for probing in the mud, spears for harpooning fish and eels... A pelican's pouch is a highly elastic scoop, expanding under water to accommodate up to thirty pints of water with its catch. The flamingo uses its sieve-like beak to dredge the mud for the microscopic crustaceans which contain a dye that keeps flamingo feathers pink. And the skimmer bird, with a protruding lower beak, literally skims on the wing. But the most unusual and beguiling of beaks must belong to the toucan. It may be an impressive showpiece, but makes a hazardous piece of cutlery, requiring a long

wire-like tongue to flick food down its throat. Enjoying the fruit of its labors, the chick makes it small but momentous entrance into the world, only to face the next obstacle. After 30 days in the shell, stretching and straightening its egg-shaped body is no easy feat. The wax coating, which protected the duckling's feathers in the shell, starts to dry immediately, allowing the feathers to fluff up and insulate the tiny newborn. All birds have feathers and no other creatures possess them. To hold or wear the bird's feathers is to possess its power. The Central American Aztecs are just one of the many cultures that have used feathers to adorn their ceremonial headdresses. Birds also use their feathers for ceremonial occasions,

such as courtship. The riot of color in a peacock's tail is focused on one purpose: attracting a mate, and the rules of courtship in any society, bird or human, can be quite a performance. (music) (music)

(music) (music) (music) The fine of courtship is followed by the more practical art of nesting. (bird calls) Perhaps one of the most unusual nest builders is the African Weaverbird. It actually sews threads with its beak and ties knots to weave the nest, which includes a long entrance tube to deter unwelcome visitors. Collecting their building materials from nearby rivers, cliff swallows construct their nests from mud. These masons of the bird

world meticulously fashion layer upon layer, making sure the mixture is just the right consistency, especially important when plastering the roof. And there are some who say that it was the golden bowerbird that introduced us to interior design. To attract a female, the male finishes off his nest by decorating it with flowers and feathers. His discerning eye pays attention to every detail with an aesthetic sense that any artist would envy. And some culinary artists do. The Chinese have been making bird's nest soup for centuries. Ground nesting birds like this duckling hatch in a more developed state than most birds. Being on the ground makes them easy prey for predators, so the sooner they're capable of flight, the greater their chances of survival. But first this chick has to learn to stand and finding your feet for the first time can prove an

exhausting business. For its tree-dwelling cousins, leaving the nest can be just as perilous as leaving the shell. Birds have to learn to fly, just as we have to learn to walk, by using the age old method of trial and error. With its first unsteady steps, a duckling sets out on life's journey. Soon it will achieve the perfection of feathered flight first mastered by its ancestor Archaeopteryx. As long as birds reach for the heavens, our imagination will soar along with them. (outro music) Presentation of this program was made possible by the Corporation for Public Broadcasting and by annual

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