Reproduction and development of birds. Development of the egg and embryo.

Reproduction in birds is sexual, fertilization is internal, and development is direct. Birds are oviparous animals.
According to the development of birds, they are divided into brood and nesting. The chicks of brood birds have the ability to see, are covered with downy plumage, and are capable of movement. Parents of brood birds keep chicks warm and also help in finding food. In nesting chicks, the chicks hatch helpless and blind (for example, a sparrow, woodpecker) and remain with their parents for up to 2 months.