The expression "to bury your head in the sand" refers to the mistaken belief that ostriches try to escape danger by pretending it isn't there.
Source of this saying is Pliny the Elder who first recorded it.
In fact, the opposite is true. Ostriches are big, strong and fast. They don't need to be afraid and hide.
They do lower their heads to scan the horizon.
Bonus fact:
They have double kneecaps - and nobody can explain why.