An illustration of a fractionally (and I mean fractionally) higher viewpoint.
There was a comment on the previous upload from this series that the effect was overdone as too much grass was blurred and therefore did not look natural. Well there was no effect, it was natural and this image addresses the key concern of the poster.
As I explained on that image grass on the same plane as the bird is sharp, it was just obscured by the grass in front, so completely an optical illusion.
Anyway this and the variant show that at the same aperture, a slightly higher viewpoint exposes a fraction of the grass in focus.