The pitch that was/is used for regular clay birds is poisonous to swine. The Bios do cause the grass and vegetation where thay degrade to die, as Larry said. The reason is that they are made mostly of sulfur, I am told, which degrades and is absorbed into the soil, lowering the pH to the point that the soil becomes so acidic that nothing can grow. Lime in sufficient quantities will raise the pH back to an acceptable range and the vegetation will once again grow.

Stan

May God bless America and those who defend her.