According to National Geographic Kids, ostriches do not stick their heads in the sand. The misconception could stem from the unique physical attributes of ostriches, or it could be the result of their unusual actions during nesting or when frightened.
The misinterpretation possibly developed because the birds have small heads that are not clearly noticeable from a distance when ostriches are feeding from the ground. Another explanation for the mistaken belief potentially arose from ostriches' nesting habits. The females lay their eggs in dirt holes and then stick their heads in regularly to turn the eggs. One Kind suggests another behavior that encourages the myth. Ostriches sometimes react to threats by stretching their necks out on the ground in an attempt to hide. The light-colored feathers on their head and neck help them blend in with their surroundings.