When threatened, ostriches bury their heads in sand to hide or avoid danger.
Ostriches don't have the anatomical ability to bury their heads in sand effectively, and they don't do so to hide. What people observe is ostriches lowering their heads into holes they've dug to tend to eggs or to retrieve food from the ground. Ostriches are actually quite aggressive when threatened and will run at high speeds or kick with their powerful legs.
Reception
Sources
- Smithsonian Magazine: Ostrich Myth REFERENCE
- National Geographic: Ostriches REFERENCE