I recently purchased a 6+ acre farmette in the county of DeKalb in the state of Illinois. On the property is a 40' X 60' pole barn. The barn is home to multiple nesting pairs of what I persume to be Barn Swallows. I want to refurbish the barn and close up the open door way that the swallows are using to fly in and out of. I do not want to displace the birds, but need the use of the barn. Can I create a inexpensive alternative structure close to the barn which would act as a new nesting ground? Are there bird houses available to purchase that would work?