BIRDS (Aves) — a class of hematothermal vertebrate animals whose front extremities in the course of evolution turned into wings. In total is apprx. 8600 types of P. belonging to 27 groups. In the USSR about 750 types of P. (18 groups) meet. On many morfol, P.'s signs are close to reptiles (see). All characteristic features of a structure of P. are connected with the ability to flight which developed at them in the course of evolution. The body at P. is covered with the feathers reducing heatlosses, giving to a body a streamline shape and forming the bearing planes (wings, a tail). Skin is dry, deprived of glands. P. have one coccygeal gland. A skeleton easy and strong that is reached by a pnevmatization and accretion of bones of some departments (e.g., skulls, sacral department). The muscles ensuring functioning of wings make from 11 to 50% of the weight (weight) of a body. Transformation of a skeleton and muscles of a backbone and the lower extremities provided a possibility of biped circulation.
Lack of teeth is characteristic of modern P.; function of a mastication of food is carried out by a gizzard. Food collects previously in the craw representing an esophagectasia. Granivorous P. swallow small stones which remain in a stomach and promote a mastication of food. Process of digestion very intensive. The thin-walled trapped air connected to lungs provides intensive gas exchange both at a breath, and at an exhalation (double breath). Circles of blood circulation are completely divided. Heart is large, averages 1% of body weight, and at views with bystry flight — to 1,5 — 2%. Heart rate can reach 1000 blows in 1 min. that provides the level of blood circulation corresponding to high metabolic rate. Body temperature 37,7 — 45,5 °. In a brain the cerebellum and hemispheres is well developed, bark is expressed poorly. From sense bodys sight and hearing are best of all developed. The basis of behavior of P. is made by difficult complexes of the congenital instinctive reflexes (see) enriched with individual experience. P.'s behavior connected with reproduction and with care of posterity, and also with migrations is especially interesting.
Items occupy practically all Earth, including anhydrous deserts, oceanic islands, severe mountain tops and polar regions. Many types of P. of moderate and subpolar latitudes twice a year make migrations (flights) of various range. Distinguish wild and house P., and also group of the synanthropic types nesting and living near the person (a blue rock pigeon, some sparrows, swallows, etc.). Value P. for the person is big and diverse. House P. are a source of meat, eggs, a feather and down. Insectivorous P. destroy arthropod wreckers, granivorous — seeds of weeds. At the same time huge packs of granivorous P. this. tkachikovy, sparrows also treat Krom, can devastate fields of grain crops. Essential danger is constituted by P. lodging near airfields because of danger of collision of airplanes with them.
Medical value of birds is defined by the fact that they can be naturally infected with viruses, bacteria, fungi, protozoa, helminths. The St. 60 causative agents of the diseases which are found at P. and important in pathology of the person are registered. High and constant body temperature, an intensive metabolism create favorable conditions for existence and proliferation of the activator in an organism of the Item. Simultaneous emergence of a large number of juveniles during the nested period leads to development of a seasonal epizooty and repeated increase in population of the activator. Clustering (packs) inherent to many types of P. during flight, feedings, a molt and reproduction also promotes dissimination of the activator among P. and to a razneseniye of an infection across huge territories.
It is possible to plan several gradation of extent of participation of P. in maintenance and spread of various infections.
- Birds are the main or only source of an infection, in particular at an ornithosis (see); most often the blue rock pigeons who are ill sometimes asymptomatically are a source of infection with an ornithosis of people in the cities.
- Birds serve as additional owners of the activator where a main role is played by mammals. Such is value P. at salmonellosises, pasteurellosis, toxoplasmosis. Especially often the role of an additional tank of an infection and a prokormitel of arthropods carriers of P. play at transmissible natural focal diseases, such as a tick-borne encephalitis, some rickettsioses (see. Natural ochagovost ).
- Birds can be involved in circulation of causative agents of purely human diseases (tuberculosis of the person, a salmonellosis).
- Birds play a role of mechanical carriers of activators of a malignant anthrax, botulism, eggs of helminths, etc. (generally it is P.'s types which are fed on dumps, garbage cans — vranovy, pigeons and other synanthropic types). Also the hypothesis is offered, according to P.'s cut participate in processes of genetic transformation of various strains of influenza viruses of the person and animals therefore emergence and distribution epidemic of dangerous options of flu is possible.
Prevention of the diseases extended by P. consists in constant vt. and dignity. supervision in poultry-farming farms and in places of accumulations of synanthropic types of the Item.
Bibliography: Life of animals, under the editorship of L. A. Zenkevich, t. 5, M., 1970; Ivanov A. I. and Shtegman B. K. Short determinant of birds of the USSR, L., 1978; Kartashev N. N. Systematics of birds, M., 1974, bibliogr.; Lviv D. K. and Ilyichev V. D. Migrations of birds and transfer of causative agents of infections, M., 1979; Mikheyev A. V. Biology of birds, M., 1960; Birds of the Soviet Union, under the editorship of G. P. Dementiev and N. A. Gladkov, t. 1 — 6, M., 1951 — 1954; V. E. Flint, etc. Birds of the USSR, M., 1968; Peters J. L. Check-list of birds of the world, v. 1 — 15, Cambridge, 1931 — 1970.
G. A. Sidorova.