[squirell nutkin]

I'm not sure if you have a hole plugging plan in place, but may I suggest coarse Bronze wool and expanding foam? In the spring you can get outside and fix the boards properly but for now if you take coarse bronze wool (doesn't rust, get it at a paint supply store or a boatyard) and gently pull it apart so it very loosely fills the hole, then you spray expanding foam into the mess of wool it will expand and create a nice foam plug that noone will want to chew through.