In the article we will talk about what are the structural features of birds, what is their skeleton. Birds are interesting in that the only group of vertebrates (except for bats), capable of not just flying in the air, but 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 found in all three environments. Not only the skeleton of the bird, but also the feathers play a role in this. The main event that provided these creatures with prosperity was the development of their plumage. Therefore, we will consider not only the skeleton of a bird, but also briefly talk about it.
Like wool in mammals, feathers first appeared as a heat-insulating cover. Only a little later did they transform into bearing planes. The birds dressed in feathers, apparently, millions of years before they gained the ability to fly.
Evolutionary changes in the structure of birds
Adaptation to flight led to the restructuring of all systems of organs and behavior. The skeleton of the bird has also changed. The photo presented above is an image of the internal structure of a pigeon. 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 were transformed into thin curved plates, retaining sufficient strength to perform their intended functions. Heavy teeth were replaced by a light beak, while the feather cover is a model of lightness, although it can weigh more than a skeleton. Between the internal organs are located participating in breathing air sacs.
Features of the skeleton of a pigeon
We offer a detailed look at the skeleton of a pigeon. It consists of pelvic bones, wing bones, caudal vertebrae, trunk, cervical spine and cranium. The head, crown, forehead, beak and very large eye sockets are distinguished in the skull. The beak is divided into 2 parts - the upper and lower. They move separately from each other. The cervical spine includes the base of the neck, pharynx and neck. The skeleton of a pigeon in the dorsal part consists of sacral, lumbar and thoracic vertebrae. Breast - from the sternum, as well as 7 pairs of ribs attached to the thoracic vertebrae. The caudal vertebrae are flattened and attached by discs consisting of connective tissue. Such, in general terms, is the skeleton of a bird. His scheme was presented above.
Bone skeleton conversion
The transformation of the bone skeleton, associated with the walking of birds on the hind limbs and the use of the front for flight, is especially pronounced in the shoulder and pelvic girdles. The shoulder girdle is rigidly connected with the sternum, and therefore, when flying, the body hangs on wings as if. This is achieved due to the greatly expanded coracoid bones, which are absent in mammals.
The skeleton of the bird has a markedly strengthened pelvic girdle. The hind limbs hold these animals well on the ground (on branches when climbing or on water when swimming) and, most importantly, successfully absorb the impacts at the time of landing. As the bones became thin, their strength increased as a result of fusion with each other, when the structure of the skeleton of the bird changed. As in mammals, three paired pelvic bones merged with the spine and with each other. There was a merger of the trunk vertebrae, starting from the last pectoral and ending with the first caudal. All of them became part of a complex sacrum, which strengthened the pelvic girdle, allowing the limbs of birds to carry out their functions, without disrupting the work of other systems.
Limbs of birds
Limbs should also be considered, characterizing the structure of the skeleton of a bird. They are strongly 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 extend along the front of the knee, then along the back of the forearm and the lower surface of the fingers. When the fingers are bent, when the bird grabs the branch, the tendon mechanism locks them, so that the grip does not weaken even during sleep. In its structure, the hind limb of the bird is very similar to the human leg, however, many of the bones of the lower leg and foot have grown together.
Brush
Describing the features of the skeleton of birds, we note that especially sharp changes in connection with adaptation to flight occurred in the structure of the brush. The remaining bones of the forelimbs are fused, forming a support for the primary feathers. The surviving first finger is a support for the rudimentary wing, which acts as a special regulator that reduces wing drag at low speeds. Minor feathers are attached to the ulna. Together with the wonderful arrangement of the feathers themselves, all this creates a wing - an organ characterized by high efficiency and adaptive plasticity. Below is the skeleton of a dodo bird extinct in the 17th century .
Wings
Fly and steering feathers provide lift and flight control, but their aerodynamic properties are not yet fully understood. During normal flapping flight, the wings move down and forward, and then sharply up and back. When it strikes down, the wing has such a steep angle of attack that it would extinguish speed if the primary fly feathers did not act at that time as an independent bearing plane, which prevents braking. Each feather rotates up and down along the rod, so that a resulting forward thrust is created, which is facilitated by the extension of their ends. In addition, at a certain angle of attack, the wing is retracted forward from the front of the wing. This forms a cut that reduces turbulence above the bearing plane and thereby suppresses braking. Landing, the bird first extinguishes speed, placing the body in a vertical plane, pulling back the tail and slowing down the wings.
The structural features of the wings of various birds
Birds that can fly slowly have particularly well-defined gaps between the primary flyworms. For example, in a golden eagle (Aquilachysaetos, pictured above), the intervals between feathers make up to 40% of the total wing area. For vultures, a very wide tail creates additional lift when hovering. Another extreme compared to the wings of eagles and vultures is the long and narrow wings of seabirds.
For example, albatrosses (the photo of one of them is presented above) almost do not flap their wings, hovering in the wind and diving, then soaring soaring upward. Their flight method is so specialized that in calm weather they are literally chained to the ground. Hummingbird wings carry only primary wing feathers and are able to make more than 50 flaps per second when the bird hangs in the air; while they move forward and backward in the horizontal plane.
Feather cover
The feather cover is adapted to perform a variety of functions. So, hard fly and tail feathers form wings and tail. And covering and contouring give the body of the bird a streamlined shape, and the fluff is a thermal insulator. Laying on each other, like tiles, feathers create a continuous smooth cover. The fine structure of the pen, to a greater extent than any other anatomical features, provides birds with prosperity in the air. The fan of each of them consists of hundreds of beards located in one plane on both sides of the rod, and from them also on both sides go out barrels carrying hooks from the side remote from the bird's body. These hooks cling to the smooth barbs of the previous row of barbs, which allows you to keep the shape of the fan unchanged. On each fly feather of a large bird, there are up to 1.5 million barbs.
Beak and its meaning
The beak serves the birds as a manipulating organ. Using the example of a woodcock (Scolopaxrusticola, one of them is shown in the photo above), one can see how complicated the actions of the beak can be when a bird immerses it in the soil, hunting for a worm. Having stumbled upon prey, the bird, by contraction of the corresponding muscles, shifts forward the square bones that make up the jaw arch. Those, in turn, push the cheekbones forward , which cause the tip of the beak to bend upward, there is an oval hole through which the tendon of the subclavian muscle passes, attached to the upper side of the shoulder. Thus, with the contraction of the subclavian muscle, the wing rises, and with the contraction of the pectoral muscles , it drops.
So, we have outlined the main structural features of the skeleton of birds. We hope you have discovered something new about these amazing creatures.