It appears they're choking, but I'm pretty sure the crop and any grit-type stuff they've eaten chops the grass and it breaks off. Some people suggest cutting grass into tiny pieces for little chicks if the mom's not there to do it for them. I've never heard of a chicken dying or choking to death from grass - I don't think the species would have survived this long if they could die from eating grass! I know it looks disturbing to watch one struggle w/a piece of grass, but they should be fine. Also - the esophogus (to the crop) and the trachea (to the lungs) are separated better than in people, so choking (blocking the trachea and breathing) shouldn't be a problem.