yes good pint we should remeber not to give the birds to much of oil's a light coating once a week of mixed cold pressed oils stored in the fridge is enough , then make sure all the food with oil is cleared and not left in the loft
easy to make, or run a jig saw around the partition in the nest box you have then put it back (on a hinge) back to where you cut it from then just drill a one inch peep hole in it