In 99 AG, ostrich horses were a common sight in the military of the Earth Kingdom, as they were used by a group of Earth Kingdom soldiers during their attempt to escort Iroh to Ba Sing Se following his capture by Gow and his men. They were also present in large numbers at General Fong's fortress, and the Royal Earthbender Guards stationed at the Earth Kingdom Royal Palace employed these animals as cavalry mounts as well. Additionally, shortly after the end of the Hundred Year War, General How and several guards rode the creatures during the Earth Kingdom military's march to Yu Dao.
Reliance on ostrich horses as a primary means of transportation was not restricted solely to the military, as they were common among civilians as well. After Zuko and Iroh became fugitives of the Fire Nation, the former stole an ostrich horse from Song's home to use as a mount during their travels in the Earth Kingdom. The animal remained with Zuko on his journey after he temporarily departed from his uncle. In Ba Sing Se, people could make use of carriages drawn by ostrich horses to traverse the large metropolis.
The use of ostrich horses also extended to be multicultural, exhibited by the fact that Fire Nation soldiers kept several ostrich horses in some of their colonies, including the coastal colony from which Zuko, Azula, Ty Lee, and Mai departed for the Fire Nation mainland following the Coup of Ba Sing Se. The beasts had also made it to the mainland, as the Fire Nation's domestic forces used ostrich horses in 102 AG to escort a decoy caravan from the harbor to the Fire Nation Capital in an attempt to draw out members of the New Ozai Society.
Although technological advances were omnipresent, even in 128 AG ostrich horses continued to be a common method of transportation in cities, as Yakone escaped his trial in Republic City by way of an ostrich horse-drawn carriage after bloodbending all the attendees in City Hall. However, the mount and the carriage were separated shortly thereafter by an airbending blast from Avatar Aang.
Ostrich horses are bipedal creatures exhibiting both ratite and equine characteristics. They exhibit morphological traits including elongated and robust hind limbs typically characteristic of a cursorial lifestyle.
They also bear a modified anisodactyl toe arrangement, with a hallux facing backward and two functional digits facing forward, all of which have claws. These powerful hind limbs allow ostrich horses to maintain high speeds over long distances, jump considerable heights, and run short distances along vertical surfaces.
The ostrich horse has a robust body and possesses short elliptical wings, accounting for its flightlessness. It has an elongated head with a broad beak that is strongly decurved, two ears located posterior to the orbit, and a thick neck.
Ostrich horses are covered almost entirely of coarse brown feathers. The only exceptions are the head region covered by coarse tan hair and the caudal region, which can consist of either white or brown hair. The head can also be covered with a mane appearing either white or tan in coloration. Short manes extend from behind the ears to the middle of the neck, whereas long manes extend from behind the ears to the shoulders. The wing tips also vary among individuals, as they can appear either brown, tan, or white in coloration.
The ostrich horse is a docile creature used extensively by people all over the world as a cavalry mount, beast of burden, or form of transportation. Particularly, highly trained ostrich horses equipped with armor serve as the primary mount of the Earth Kingdom military and are often used in battles by several divisions. Ostrich horses used by the military appear in body armor that covers their heads, necks, and parts of their sides.
Civilians also equip domesticated ostrich horses with saddles and use them to pull carriages and other vehicles, primarily to serve as a form of transportation, but also as a means of carrying supplies and transporting goods.
Although they have a generally calm temperament, ostrich horses have been known to buck and kick their riders as well as nearby bystanders when startled or agitated. Wild ostrich horses are solitary and can be found near human settlements.
The ostrich horse exhibits characteristics from both of its namesakes. Although the ostrich horse retains the general avian body structure, it exhibits traits seen in horses, including an odd number of functional digits, a third trochanter on the femur, and hair as the primary body covering. Ostrich horses bear resemblance to many ratites, which includes the order to which ostriches belong. The equine characteristics which it exhibits can also be attributed to many members of the Equidae family, which includes horses, donkeys, and zebras. The ostrich horse also bears resemblance to several extinct species of flightless birds such as the Gastornis or the terror birds of the Phorusrhacidae family.
- After the Hundred Year War, a pro-bending team named itself the Orchid Gardens Ostrich Horses.
- Before cars were invented, ostrich horses pulled people in carriages, much like horses in the real world did before cars were invented.
- The ostrich horse was featured in one of the first films in the World of Avatar. This parallels the real world development of moving pictures, as one of the first films to be produced was that of a galloping horse.
- While growing up on a farm, Varrick owned an ostrich horse named "Mrs. Beaks".