The Bird and His Hole

We are in the middle of doing some major work in our home. One of the things involved is a wall cut down in half. The bird is always getting himself into little nooks and crannies (it is in their nature to "burrow" into small places and nest). So this morning he has discovered the top of this new half wall, which is not even topped off yet, and sees these holes. I think he has found a new perch:



So why do they say ostriches stick their heads in holes?