Birds are vertebrates
HABITAT AND GEOGRAPHICAL DISTRIBUTION
Thanks to the ability of most species to fly, birds have been able to spread almost everywhere in the world, colonizing almost all the surfaces of the earth and even the seas.
Few species of birds are sedentary, that is to say that they live in the same place throughout their lives, many make the classic migrations linked to the trend of the seasons. Generally they have precise geographical areas but there are species that even span different continents (for example the peregrine falcon).
Birds are characterized by the fact of having the body that is supported by only the hind limbs while the front ones have transformed into wings generally on the fly but not in all species (eg penguins and ostriches). This feature is not actually exclusive to birds, in fact we have mammals that can fly, such as bats or insects. Their peculiarity is the body covered with feathers (which serve to retain body heat, small in size that cover the chicks and the innermost layer of the adult plumage) and feathers (they are the bearing surfaces in flight, large in size) except of the paws that are instead covered with scales. Bird species that live in particularly harsh environments generally have denser plumage than those that live in warmer environments.
In addition to playing a fundamental role in the anatomy of birds, plumage is also fundamental for their social life. In fact, it plays an important role, for example during courtship rituals or in performances between males, for the purpose of intimidating a territory or a female, for these reasons, in general, males have a much more colorful plumage than females. The plumage has a very important role in camouflage: the classic example is the parchment which is the only bird whose plumage turns white in winter to blend in with the snow.
They have a beak, a corneous case more or less developed according to the type of feeding, which covers the jaws and are devoid of teeth.
Another peculiarity of birds is the fact that they have a particularly developed sternum, generally with a sort of crest (keel) which serves for the insertion of the pectoral muscles that support the wings and therefore fundamental for flight (this crest in birds that have lost the ability to fly is absent).
In consideration of the fact that most birds fly, the bones are particularly light and this is due to the fact that they have diary-filled cavities that communicate with air sacs which are protrusions of the lungs which also extend into the abdomen and thorax which filling with air make the body lighter and facilitate breathing during flight. Furthermore, the passage of air between these structures allows the dispersion of excess heat, not having sweat glands in birds as in mammals.
They have very acute eyesight and the eye is shaped in such a way as to be able to perceive very distant objects.
Another peculiarity of the birds is the syringe, an organ placed at the bifurcation of the bronchi in charge of singing.
The substantial difference with mammals is that birds are oviparous that is to say that the young are born from fertilized eggs, normally laid by the mother inside a nest (to protect them from bad weather and predators), where they are hatched by one of the two parents (or from both) until the birth of the offspring.
The eggs of birds vary in size depending on the species but all are covered with a calcareous and porous shell.
The number of eggs is very variable from 1 to a maximum of 20.
BEHAVIOR AND LIFESTYLES
Some peculiarities of the bird world is that most species are monogamous either for life or for the breeding season.
Migration is quite widespread and linked to the cycle of the seasons: when the cold season approaches, birds tend to migrate to warmer areas. Few species are stationary, that is, they live their whole life in the same place where they were born.
Birds can be solitary or gregarious.
The song in birds, more or less melodious depending on the species, is an important element of inter and intraspecies communication in fact it serves to specify the species to which it belongs (each species has its own tonality); sex; the reason for the song (delimitation of the territory, sexual appeal) and the individual characteristics of the person who emitted them.
Below are the monographic files of the main birds.
Individual bird species information sheets