Most birds fly in the air by wings, while some birds don't live by flying. For example, ostrich is a large bird on the grassland and the largest bird in existence, weighing more than 100 kg, reaching more than 2 meters. So the ostrich's huge body is one of the reasons to stop it from flying.

The ostrich's flying organs are different from other birds, which is another reason why it can't fly. The flying organs of birds mainly include wings and feathers evolved from forelimbs. Among feathers, flying feathers and tail feathers do have the function of flying. Flying feathers grow on wings and tail feathers grow on tails. This feather consists of many slender branches, which are densely covered with rows of branches, and there are hooks on the branches to hook the feathers to form feathers.

Feathers fan the air and make birds fly in the air. Tail feathers born at the tail can also be connected with feather hooks to play the role of rudder in flight. In order to maintain the normal function of birds' flying organs, they also have a caudate gland, which secretes oil to protect feathers from deformation. The way the feathers of birds fall on the body surface is also very particular.

Feathers are generally divided into feathered areas and featherless areas, that is, feathers are distributed in some areas of the body surface, and some areas are not feathered. This feathering mode is conducive to powerful flight movements. Ostrich feathers have neither flying feathers nor tail feathers, and there is no feather maintainer-tail gland. Feathering patterns are evenly distributed on the body surface, and there is no distinction between feathering areas and bare areas. Its flying organs are highly degraded, so it is impossible to fly.