First, a detailed interpretation:
Birds are a subclass of vertebrates, which is the general name of all birds and animals. The body is streamlined and the skin is thin and elastic; The body is covered with feathers, generally the forelimbs become wings, and some kinds of wings degenerate; The pectoral muscles are developed; Short rectum; The heart has two atria and two ventricles, and its temperature is constant.
Under the condition of artificial feeding, the life span of large birds is 30-50 years, that of medium birds is 20-30 years, and that of small birds is 10- 15 years.
Second, the feather structure of birds:
Feathers are divided into normal feathers and down feathers. Feather branches are densely distributed on both sides of the feather branches, and there are hooks or grooves on the feather branches, and adjacent feather branches are hooked with each other to form a flat and elastic feather sheet. The positive feathers on the body surface form a windbreak shell, which makes the bird's body streamlined. Positive feathers on wings and tails play a decisive role in flight and balance.
The structural characteristics of down feather are that the shaft of down feather is long and thin, and the hook-like protrusions of down twigs are underdeveloped, which can not form solid feathers and has the function of heat preservation. Duck down is duck down. Hairiness is very thin, like hair, mixed with normal feathers and down, which can only be seen after the normal feathers and down are removed.
Living habits of birds:
1, birds have a variety of foods:
Include nectar, seeds, insects, fish, carrion or other birds.
2. The activity time of birds:
Most birds move during the day, and some birds move at night or dusk. Many birds migrate long distances to find the best habitat, and some birds spend most of their time at sea.
3. Flying:
Most birds can fly, but a few flat-breasted birds can't, especially the birds living on the island, which have basically lost their ability to fly. Flightless birds include penguins, ostriches, kiwis and extinct dodos. When humans or other mammals invade their habitats, these flightless birds will become extinct more easily.
4. Migration:
Every spring and autumn, birds fly in groups in the sky, covering the sun. This seasonal phenomenon of changing habitats in different seasons, or moving from nesting sites to wintering sites, or returning from wintering sites to nesting sites is called bird migration.