What Is A Bird? (1962)

[Applause] [Music] [Applause] the gull is a fitting symbol of more than 9,000 different species of birds that have made a success of survival in a wide variety of environments it is at home in the air or as well as on the GR or in the [Applause] water a warm blooded vertebrate with a covering of feathers this is one of the classic definitions of a [Applause] bird what isn't generally realized however is that the light fluffy feather of a bird is closely related to the scale of a reptile in fact feathers have the same chemical composition as scales this has given rise to the expression that birds are glorified reptiles a comparative study of living reptils and birds and the fossil remains of their prehistoric ancestors indicates similarities of evolutionary development for instance the skeleton of one of these ancient reptils the ornithos suus Bears some striking similarities to the skeleton of a bird this reptile walked on its hind legs and had a pelvic bone very much like that of the earliest known bird the arch opter meaning ancient winged one this extinct bird of the Jurassic period possessed many reptilian features the birdlike lower jaw had small teeth the evolution of the bird's beak had not been completed the vertebrae of the pelvic region and backbone had not yet fused also the arch opter had a long bony tail which had persisted from its reptilian forebears however the archaeopteris did have wings equipped with three unfused digits or claws which had persisted from earlier forms bones and wings further adapted to requirements of flight as evidenced in this skeleton of a present day pigeon many of the larger bones of a bird are Hollow and light similarly increased lightness results from the reduction in size of the Jawbone and the absence of teeth the present day bird has a beak a large Keel on the breast bone acts as an anchor for the muscles of flight Air sacks located in many parts of the body provide for improved respir Iration and lightness but lightness alone is not enough to sustain a bird in Flight flying is a strenuous activity to support the faster metabolism necessary to sustain flight a four chambered heart evolved from the three-chambered heart of the reptils through the development of a complete partition between the ventricles the cerebellum is more highly developed in Birds than in reptils and mammals and is related to Swift control and balance during flight Wings attached to the bird's center of gravity also help it achieve balance the cross-section of a bird's Wing would look like this we call this shape an air foil as the streamlined Wing moves rapidly along air rushes over both the top and bottom surfaces because of the curvature of the upper surface of the wing the air along this surface has to move faster this creates lift the shape of the bird further helps it maintain flight its body is so built that it reduces wind resistance to further cut down wind resistance the legs of the bird are pulled up close to the body when the bird is in flight to protect its delicate eyes from wind and dust dust during flight without interrupting Vision birds are equipped with a nictating membrane shown here in Freeze Frame photography this thin covering constantly cleanses the eye yet unlike the eyelid does not cut off Vision a covering of feathers not only has the advantage of lightness but also serves as insulation from cold and heat in this laboratory setup we can watch this bird ruffle its feathers as protection against the cold of the surrounding ice ruffling of feathers increases dead air space around the bird's body thereby insulating it from the cold besides these special properties of feathers some species exhibit their feathers as a sex display others have feathers that naturally blend with the color of the surroundings concealing them from enemies note how the pheasant's feathers help it hide among the fall leaves all through these evolutionary stages Birds continued to lay eggs like their reptilian ancestors in this way the young could develop outside the mother's body leaving her unburdened for flight after the eggs have hatched the mother bird can leave its young and fly off in search of food unlike reptiles most birds incubate their own eggs when laying the eggs the incubating parent sheds many breast feathers thus exposed the skin becomes inflamed and warms the eggs for proper development along with laying eggs a nest building Instinct evolved some birds such as the robin build a new nest for each clutch of eggs even when there is an old unused Nest nearby certain other birds such as the Osprey maintain the same nest year after year usually at a site which affords a commanding view for its predatory eye some swallows build their nests at the end of tunnels they dig in banks of Earth hence their name Bank swallows this nest in a dead tree stump belongs to a tree swallow not all birds however build nests the Cowbird leaves its speckled eggs in other birds nests unknowingly the parent Robin will hatch the Cowbird eggs and feed the young along with its own parental feeding of the nesting young is instinctive most newborn nesting birds are unable to feed themselves and would die if left unattended some birds however can feed themselves shortly after hatching usually we associate birds with flying but not all birds fly flippers help the penguin get about on land as well as underwater indeed the flippers make it possible for the penguin to literally fly underwater the wings of this bird also have lost their original function but the ostrich has another adaptation to Life as a land animal the foot of the ostrich is almost hoof-like having only two of its original four toes this type of foot and its very elongated legs enable the ostrich to move easily over hard ground these adaptive features have made the Ria a South American relative of the ostrich a fast moving Target in the gao's favorite sport of throwing the Bola the duck is adapted to life on another substratum webbed feet enable it to paddle about with ease and speed the Jana's feet enable it to literally walk on water plants where it can find many kinds of insects to feed upon these toes two in front and two in the rear help the Woodpecker cling to tree trunks where it can find food Talons like these sharp and strong enable the hawk to be one of the top carnivores in the environment in which it lives Talons and hooked beak enable it to catch and tear at the Flesh of its prey the parrot's beak is adapted to a function indirectly connected with food Gathering it helps the parrot to move around on tree limbs where it usually lives the flamingos bent Bill however is adapted to another means of food gathering this bird obtains its food by straining Plankton and worms from the soft mud of the marshes in which it makes its home the Pelican is an example of a bird uniquely adapted for its dependence on fish its great wings and Bill pouch enable it to carry off whole fish that it catches possibly most distinctive of all is the tubik beak of the hummingbird which enables it to draw in the nectar from flowers in every environment niches will be found that are filled by birds in each case these birds are uniquely adapted by beak size coloration feet and other aspects of their body plan also each species of bird is ad Ed to survive by Behavior patterns that are inborn such as the killer distracting its Enemy by figing injury in order to protect its nest many species use songs to mark off territories wherein each male bird seeks to maintain its own ascendancy warning off competing birds and attracting potential mates others perform elaborate ritual dances by this annual dance the male sharptail Grouse competes for First Choice of the [Music] [Music] hens instinctive Behavior patterns characteristic of each species of bird include those for nesting care of the young and in the case of the wild goose migration migration is the seasonal passage of birds from one region to another this seasonal phenomenon is the subject of much study what factors trigger this behavior for example is the changing length of daylight a factor are changes in the conditions of the reproductive organs a factor in this laboratory the daily hours of light and dark can be regulated the relationship between the length of daylight and the seasonal habits of the birds is studied the birds in these cages are bobbl links a migratory species here a variety of phenomena related to migration habits are investigated the problem is to learn the relationship if any between the period of life and the condition of the reproductive organs this bird is being anesthetized for a smear test of sperm to see how far the sperm have matured such maturation of the sperm and the accompanying increase of body fat are signs of approaching Readiness for migration what exactly triggers a mass migration of birds over a large geographical region is still the subject of continuing research Readiness for migration is also studied in this experimental setup these interconnecting cages are so constructed that they face in all major directions of the compass every time the bird enters any one of the cages its entrance is counted as the period of migration approaches the bird tends to enter one cage more frequently indicating the probable direction of migratory flight many questions are still unanswer how do birds find their way during migration are they sensitive to the magnetic field of the Earth have they some other means for orientation do they navigate by the sun and stars many experiments are being conducted in search of a better understanding of migration and other aspects of bird Behavior