If by empty you mean nuts never developed in the hull and not something ate them all , perhaps the trees are lacking proper minerals in the soil. If this is the case, do some research on them, and fertilize a group of trees where you plan to hunt. From what I've read, deer will go to a beech nut before any available food, but we don't have any around us so I have no idea if this is true. If it is, you could create an early season gold mine.