In the article we will talk about the structural features of birds, what is their skeleton. Birds are interesting in that they are the only group of vertebrates (except bats) capable of not just hovering in the air, but of real flight. Their structure is well adapted for this purpose. Being masters of the air, they feel great both on land and on water, and some of them, ducks for example, are in all three environments. Not only the skeleton of the bird plays a role in this, but also the feathers. The main event that ensured the prosperity of these creatures was the development of their plumage. Therefore, we will consider not only the skeleton of a bird, but also briefly talk about it.
Like mammalian fur, feathers first arose as a heat-insulating cover. Only a little later they were transformed into bearing planes. Birds dressed in feathers, apparently millions of years before they were able to fly.
Evolutionary changes in the structure of birds
Adaptation to flight led to the restructuring of all organ systems and behavior. The skeleton of the bird has also changed. The photo above is the imageinternal structure of a dove. Structural changes were manifested mainly in an increase in muscle strength with a decrease in body weight. The bones of the skeleton became hollow or cellular, or transformed into thin curved plates, while maintaining sufficient strength to perform their intended functions. The heavy teeth were replaced by a light beak, while the feather cover is an example of lightness, although it can weigh more than a skeleton. Between the internal organs are air sacs involved in breathing.
Features of the pigeon skeleton
We offer a detailed look at the skeleton of a dove. It consists of the pelvic bones, wing bones, tail vertebrae, torso, cervical region and cranium. In the skull, the back of the head, crown, forehead, beak and very large eye sockets are distinguished. The beak is divided into 2 parts - upper and lower. They move separately from each other. The cervical region includes the base of the neck, pharynx and neck. The pigeon skeleton in the dorsal part consists of the sacral, lumbar and thoracic vertebrae. Chest - from the sternum, as well as 7 pairs of ribs attached to the thoracic vertebrae. The caudal vertebrae are flattened and attached by discs composed of connective tissue. Such, in general terms, is the skeleton of a bird. Its scheme was presented above.
Bone transformation
The transformation of the bone skeleton, associated with the walking of birds on the hind limbs and the use of the forelimbs for flight, is especially clearly expressed in the shoulder and pelvic girdle. The shoulder girdle is rigidly connected with the sternum, and therefore, during the flight, the body seems to hang on the wings. This is achieveddue to overgrown coracoid bones, which are absent in mammals.
The bird's skeleton has a noticeably reinforced pelvic girdle. The hind limbs hold these animals well on the ground (on the branches when climbing or on the water when swimming) and, most importantly, successfully absorb blows at the moment of landing. Since the bones became thin, their strength increased as a result of fusion with each other when the structure of the bird's skeleton changed. As in mammals, three paired pelvic bones fused with the spine and with each other. There was a fusion of the trunk vertebrae, starting from the last thoracic and ending with the first caudal. All of them were part of the complex sacrum, which strengthened the pelvic girdle, allowing the limbs of birds to perform their functions without disturbing the work of other systems.
Bird limbs
The limbs should also be considered, characterizing the structure of the bird's skeleton. They are highly modified in comparison with the typical features characteristic of vertebrates. So, the bones of the metatarsus and tarsus lengthened and merged with each other, forming an additional segment of the limb. The thigh is usually hidden under the feathers. The hind limbs have a mechanism that allows birds to stay on the branches. The flexor muscles of the fingers lie above the knee. Their long tendons run along the front of the knee, then along the back of the tarsus and the underside of the fingers. By bending the fingers, when the bird grabs the branch, the tendon mechanism locks them, so that the grip does not weaken even during sleep. By its structure, the backthe limb of a bird is very similar to a human leg, but many of the bones of the lower leg and foot are fused.
Brush
Describing the features of the skeleton of birds, we note that particularly dramatic changes in connection with adaptation to flight have occurred in the structure of the hand. The remaining bones of the forelimbs have grown together, forming a support for the primary flight feathers. The preserved first finger is the support for a rudimentary winglet, which acts as a special regulator that reduces wing drag at low flight speeds. Secondary flight feathers are attached to the ulna. Together with the wonderful structure of the feathers themselves, all this creates a wing - an organ characterized by high efficiency and adaptive plasticity. Below is the skeleton of a 17th-century dodo bird.
Wings
Fly and tail feathers provide lift and control in flight, but their aerodynamic properties are not yet fully understood. In normal flapping flight, the wings move down and forward, and then sharply up and back. When hitting down, the wing has such a steep angle of attack that it would dampen the speed if the primary flight feathers did not act at that time as an independent bearing plane that prevents braking. Each feather pivots up and down along the stem so that a forward thrust is created, aided by the spreading of their ends. In addition, at a certain angle of attack, the winglet is retracted forward from the wing front. This forms a cut that reduces turbulence overcarrier plane and thereby damping braking. When landing, the bird preliminarily dampens its speed by positioning its body in a vertical plane, retracting its tail and braking with its wings.
Features of the structure of the wings of various birds
Birds that can fly slowly have especially well-marked gaps between the primary primaries. For example, in the golden eagle (Aquilachysaetos, pictured above), the gaps between the feathers make up up to 40% of the total wing area. Vultures have a very wide tail that creates additional lift when hovering. At the other extreme of the wings of eagles and vultures are the long, narrow wings of seabirds.
For example, albatrosses (a photo of one of them is presented above) almost do not flap their wings, soaring in the wind and then diving, then steeply soaring up. Their way of flying is so specialized that in calm weather they are literally chained to the ground. The wings of a hummingbird carry only primary flight feathers and are capable of making more than 50 strokes per second when the bird hangs in the air; while they move back and forth in a horizontal plane.
Feather cover
The feather cover is adapted to perform various functions. So, hard fly and tail feathers form wings and tail. And covering and contouring give the bird's body a streamlined shape, and down is a thermal insulator. Leaning on each other, like tiles, feathers create a continuous smooth cover. The fine structure of the pen, more so than any otheranatomical features, provides birds with prosperity in the air. The fan of each of them consists of hundreds of barbs located in the same plane on both sides of the rod, and barbs also extend from them on both sides, carrying hooks from the side remote from the body of the bird. These hooks cling to the smooth beards of the previous row of beards, which makes it possible to keep the shape of the fan unchanged. There are up to 1.5 million beards on each fly feather of a large bird.
Beak and its meaning
The beak serves as a manipulating organ for birds. Using the example of the woodcock (Scolopaxrusticola, one of them is shown in the photo above), you can see how complex the actions of the beak can be when the bird plunges it into the soil, hunting for a worm. Having stumbled upon prey, the bird, by contraction of the corresponding muscles, moves forward the square bones that make up the jaw arch. Those, in turn, push the zygomatic bones forward, which cause the tip of the beak to bend upwards, there is an oval hole through which the tendon of the subclavian muscle passes, which is attached to the upper side of the shoulder. Thus, when the subclavian muscle contracts, the wing rises, and when the pectoral muscles contract, it falls.
So, we have outlined the main features of the structure of the skeleton of birds. We hope you have discovered something new about these amazing creatures.
