Ostriches sleeping, with REM sleep and slow-wave sleep phases. Only 16 percent of common ostrich sightings were of more than two birds. They are most active early and late in the day. Lacking teeth, they swallow pebbles that act as gastroliths to grind food in the gizzard. When eating, they will fill their gullet with food, which is in turn passed down their esophagus in the form of a ball called a bolus.
After passing through the neck there is no crop the food enters the gizzard and is worked on by the aforementioned pebbles. As with other birds, an individual may reproduce several times over its lifetime. The mating season begins in March or April and ends sometime before September. The mating process differs in different geographical regions. Territorial males typically boom in defence of their territory and harem of two to seven hens;  the successful male may then mate with several females in the area, but will only form a pair bond with a 'major' female.
They will go to the mating area and he will maintain privacy by driving away all intruders. They graze until their behaviour is synchronized, then the feeding becomes secondary and the process takes on a ritualistic appearance. The cock will then excitedly flap alternate wings again, and start poking on the ground with his bill.
He will then violently flap his wings to symbolically clear out a nest in the soil. Then, while the hen runs a circle around him with lowered wings, he will wind his head in a spiral motion. She will drop to the ground and he will mount for copulation. The dominant female lays her eggs first, and when it is time to cover them for incubation she discards extra eggs from the weaker females, leaving about 20 in most cases. This uses the colouration of the two sexes to escape detection of the nest, as the drab female blends in with the sand, while the black male is nearly undetectable in the night.
This is believed to be the case due to the high rate of predation. Common ostriches in captivity have lived to 62 years and 7 months. Animals that prey on ostriches of all ages may include cheetahs , lions , leopards , African hunting dogs , and spotted hyenas. A notable exception is the cheetah, which is the most prolific predator of adult common ostriches due to its own great running speeds.
While the caudal end of the mesobronchus branches into several dorsobronchi. Together, the ventrobronchi and dorsobronchi are connected by intra-pulmonary airways, the parabronchi , which form an arcade structure within the lung called the paleopulmo. It is the only structure found in primitive birds such as ratites. Due to this the lack of connective tissue surrounding the parabronchi and adjacent parabronchial lumen, they exchange blood capillaries or avascular epithelial plates.
The use of air sacs forms the basis for the three main avian respiratory characteristics: Air is able to flow continuously in one direction through the lung, making it more efficient than the mammalian lung.
It provides birds with a large residual volume, allowing them to breathe much more slowly and deeply than a mammal of the same body mass. It provides a large source of air that is used not only for gaseous exchange, but also for the transfer of heat by evaporation. The air then flows through the anatomical dead space of a highly vascular trachea c. Inspired air moves into the respiratory system as a result of the expansion of thoraco abdominal cavity; controlled by inspiratory muscles.
During expiration, oxygen poor air flows to the anterior air sacs  and is expelled by the action of the expiratory muscles. The common ostrich air sacs play a key role in respiration since they are capacious, and increase surface area as described by the Fick Principle.
Birds lack sweat glands, so when placed under stress due to heat, they heavily rely upon increased evaporation from the respiratory system for heat transfer. This rise in respiration rate however is not necessarily associated with a greater rate of oxygen consumption.