Mine love anything leafy and green- parsley, cilantro, kale, spinach, any and all lettuces...
And what IS it with chickens and styrofoam? When we were finishing up their run last year, I put them out in a small wire pen at the bottom of the coop ramp and tried to block the top half of the pop door with a small styrofoam box. They went up the ramp into the coop just fine. And I later discovered they'd eaten about halfway thru the bottom of the styrofoam box! I would think after all the good stuff they get, the styrofoam would taste pretty bad!
Then again, I've never tried munching on styrofoam so I dunno- maybe it tastes really good?!?