It's called 'focus stacking' but you would have to sacrifice the birds - really can't have much movement in a two+ image you're going to stack. The grass could still show movement which is a good way to show that the wind is blowing while everything else stays still. Here is a link that explains it well: http://www.cambridgeincolour.com/tutorials/focus-stacking.htm

And here is some software with which to do it, some free, some not: http://www.laurieknight.net/article/view/7/

You can shoot several images at different distances between you and infinity at less than max aperture to avoid lens aberrations, stacking as many images as is required to build up to one totally focused image.