Gina I'm bout 95% sure it's a squirrel that did that. Not only do ya see it every day but mice and rats make nests from softer stuff inside other things that will be enclosed except for an entrance/exit hole. Have you ever opened a drawer or moved something and there was a big pile of shredded paper, insulation, chewed up fabric, etc. Squirrels build nests from sticks, twigs, leaves, etc. and they are more open in form. Here is a pic of a squirrel nest.
Here is a rats nest
