In a nutshell: I have no idea.
OK, here’s the long version. I’ve raised many chickens over about a dozen years now, and not one of them could resist a bit of Styrofoam packaging or a stray construction panel with Styrofoam insulation.

My chickens consume a diverse diet of layer feed, kitchen leftovers, and pasture. They choose Styrofoam over their feed, vegetable peels, fresh grass, and any food you can imagine. No, they won’t only eat Styrofoam, given the choice, but they’ll eat it before anything else.
It seems this isn’t an anomaly. Chicken owners all over the world report the same thing: their hens and roosters can’t resist Styrofoam. If I ever publish an updated edition of The Basic Guide to Backyard Livestock, I’ll be sure to include this phenomenon.
What do chickens find so appealing about Styrofoam? Its texture, I suppose. It’s easy to peck at, and when it scatters, it looks like crumbs. But surely when they taste it they should be disappointed?
Compared to humans, chickens have very few taste buds, so they don’t respond to taste the same way we do. However, they generally have an innate ability to choose nutritious foods. Styrofoam doesn’t quite fit the profile, though.
Will Styrofoam harm your chickens? I can only speak from experience. For years, I have tried to discourage my birds from eating Styrofoam. I offered distracting treats and shooed them away. I herded them out to patches of succulent fresh grass teeming with bugs. To no avail. If Styrofoam is available, they’ll come back to nibble on it. So far, my flock hasn’t sustained any visible damage.
Naturally, eating Styrofoam can’t be good for chickens. Theoretically, Styrofoam could impact a bird’s crop and cause suffocation. The only practical way to deal with this problem is to avoid leaving any Styrofoam lying around.
Do your chickens go crazy over Styrofoam too? Tell me in the comments.