Protect nesting birds and chicks in your bird houses with The Bird Guardian Birdhouse Protector! Protect nesting birds form blue jays, crows, grackles, squirrels, cats, racoons, and more! It easily attaches to your birdhouse using the three included screws. And it fits any birdhouse with a 1 to 1.5 inch opening. Menaing it can provide year 'round safety for bluejays, chickagees, nutatches, swallows, titmice, woodpeckers, wrens, and so much more!