Right it wasn't an omen or anything but it sounds like it was an actual grace, meant to remind you of the devil. God knew from all eternity that you would be in that exact situation, at that exact church, at that exact moment and see that exact bird. He knew, since He created you, what your reaction would be. Therefore, such is an actual grace meant to give you a holy fear of evil and sin. For others, this situation wouldn't mean anything because God created them to view the world differently. Nothing wrong with that either.