Some of my chickens have taken a liking to pecking at and eating the foam pipe insulation and plastic strings of tarps and sandbags (plus the sand inside them) that I have holding down my basketball hoop. Is this dangerous for them? I can’t really remove the pipe insulation because the pipes will possibly freeze and I can’t just pile the sand on the hoop base, so the bags are somewhat necessary. But I am concerned about them eating the plastic and foam because I have seen them actually eat both before I could stop them. Is there a nutritional lacking that may be causing them to eat these things when they have plenty of food and full range of a huge yard and plenty of plants to eat too?