The bird’s body is not entirely covered with feathers. Bare or nearly naked areas of the body are found on the belly

The bird’s body is not entirely covered with feathers. Bare or nearly naked areas of the body are found on the belly, sides of the body and neck. What are the names of such areas of the body and how can one explain the presence of skin areas in birds that are devoid of feather cover?

The metabolism in the body of birds is at a high level. Therefore, their body temperature is higher than that of humans. This means that there must be open areas to cool the body.
Legs are most often exposed. This feature is also important for the convenience of movement on the earth’s surface.
Some species have no plumage on the head and neck. This is due to the nature of the diet. It is important for scavengers that food debris does not linger on the surface of their bodies. It is easier to maintain cleanliness in the absence of a feather cover.