We saw a bird in Austin that we nicknamed the "mean bird", but didn't know what it was since they aren't in Chicagoland. These birds were very noisy and bullied every other bird they saw. If another type of bird was looking for food on the ground, these "mean birds" would land close to them and puff up trying to scare them off. We've never seen anything quite like this behavior.
All About Birds says they are Great Tailed Grackles
All About Birds says they are Great Tailed Grackles