After you go to sleep, bird special muscles, going to ochino (immersed in the skin to the end of the pen), sheresheva dress, raise the feathers on end, so it was warmer. Under these real, or, as experts say, contour, feathers hide a thin filamentous feathers. In the last century, thought it was pitiful remnants of the once elegant plumage. In the thirties of our century have confirmed the opinion that the filamentous feathers are not the remains, and additional insulation. But how many can give stunted feathers, scattered here and there? It took another twenty years, and ornithologists finally looked in the root: threads always grow close from the contour of the pen. Not do they help keep the dress in order? Do not pass into the bag, which sticks out of a contour feather, irritation, if the pen smato obstinate neighbor or turned a gust of wind? Yes, passed.
But filamentous feathers have a job and more serious. This was discovered after the study, the birds of 25 species, including crows, undertaken T. L. Borodulina. She found that the crow threads grow on the wings, thighs, neck and chest. On the neck of each pen hold two strings of length in the quarter master of the pen; on the breast a gentle threads even slightly longer than the neck, and also cling to a strong feathers. The situation is almost like the song, where fine Rowan wants to lean against a mighty oak.
Raven not care what is happening with feathers. And tell her about this weave nerves - sensitive calf's Herbst, who settled in the skin. But it is more correct to say: the bullock of the Herbst transmitted to the Central nervous system information about the position of the feathers and the pressure of the air streams. Themselves bullock receive signals from filamentous feathers - those, like Rowan, bend and perekrikivayutsya along with oak - strong feathers and wings, and tail. (By the way, voronja the back and belly of Taurus Herbst no.)
But what if a crow to pluck? Nothing special, of course, will not happen - like naked and then dressed. (True, naked Raven can catch a cold.) How dress crows, perhaps, knows A. A. voitkevich is the author of a voluminous work "bird Feather". Moulting is a complex thing. Signals to the "dressing up" come from the nervous system and the pituitary and endocrine glands. But most importantly, hormonal order: to crow changed the dress, it is enough to inject either progesterone or thyroidin - drug thyroid gland.
It is customary to think that first throws out the old pen and only then begins to grow a new one. Situation is Vice versa: the new stump pushes old with such force that not even help the clamps, which tried to keep possessesa feathers.
The voitkevich lot manipulated with the thyroid gland and its preparations. It was found that the introduction of hormones not only spurs shedding, but also affects the color of the feathers from large doses of the bird fades, and when small becomes brighter. Yet with hormones crow cannot razdetsya as a parrot.