Unfortunately, when it comes to bird control, grackles can be a challenge, not only because of their roosting habits but because they are prolific breeders as well. They roost in massive numbers, and thus these birds can quickly overwhelm any site where they set up their habitats, whether it is in trees or in buildings.  Indeed, the grackle is a major agricultural pest as the boisterous bird causes millions of dollars in damage to cornfields annually.