Styrofoam is like grubs to them I think. It's the texture that draws them. Probably nothing funnier than watching me chasing a hen who knows I'm going to take the piece away. She'll get a few steps ahead and smack it on the ground to try and break it while I lunge for her. They are lightning fast when they see it, too. Dart in, grab, and run like mad.
The nasty voles have been having babies lately. The hens get them right behind the neck as soon as they see a young one. Snap. Beat to tenderize then down the hatch and run while the others try and pull it out by the tail. My German Shepherd dug up a nest of the newborns and it was a free for all to see who could eat them the fastest, the dog or the chickens. Even the 5 week old chicks were in that melee. I think my walking stomach of a barred rock won since the dog eats to dainty and the chickens are willing to stick their heads in HER mouth to get whatever food she has into THEIR mouths.