Ostriches never hide their head in the sand, especially not when approached by an enemy. In fact, ostriches can become quite aggressive when threatened. According to the book "Flightless Birds" by Clive Roots, ostriches respond to predators by either running away or attacking. Ostriches have very powerful legs and have been known to kill people with a slashing kick. When fleeing danger, ostriches can reach 50 mph and can sustain a speed of 30 mph for a half hour. This myth perhaps comes from the fact that ostriches have long necks and small heads so that when they are bending over to swallow sand, it looks like their head is buried. But harboring the notion that ostriches are dumb and harmless can be a deadly mistake for humans to make.