Two nest boxes were crammed full of husked walnuts, put there by red squirrels, as here. This one was so full of nuts that it was difficult to open the door and when I did, many spilled out (I put them back). There was no room for a squirrel in this box, barely room for a mouse! A good, safe storage place, however. When we were checking one box, a red squirrel started to scold us and ran down a nearby tree branch looking rather put out.