Mine wouldn't eat them whole at first either. I tried putting some in a food processor VERY briefly and then throwing them out there - that didn't really work either. Then I cut some whole sunflower heads with seeds from the garden and gave those to the chickens - they really loved pecking the seeds out of there, and now they come running when they know I have sunflower seeds for them... I can't explain why this is, just that it happened this way. It may be that they will eventually figure it out, but maybe you could offer them one of those wild bird lard cakes with sunflower seeds in it (my chicken LOVE those, too) and that will teach them that they're delicious.