Serrin, So sorry for your loss of the blue bird family. Don't know if this would be of any use for the blue bird house, we have one of those big tractor cultivator disc on our bird feeder pole to keep the bushy tailed rats out of the bird feeder. They can not get past it. Had our Suburban suddenly quit on day when I was driving 55 mph in the rain. Why did the truck die? The mechanic found that rodents, in our case pack rats or chipmunks, had stripped the insulation of the truck's electrical wires. The splatter from the rain shorted out the truck....ever need a tow truck at noon on Thanksgiving Day? Made it to the family dinner in time for dessert. *&^%$ rodents!
Tim, my biggest concern is when they start chewing on the wiring in a house out out building. A semi feral cat decided to take up residence in our wood barn a couple of years ago, he is great with the chickens and made a major dent in the rodent population.