Around here we don't have any grackles, but we do have blackbirds that stay year round, and starlings.
Blackbirds are solid black, with black beaks.
Starlings are blackish gray with light colored flecks, and have a yellow beak.
They are both the same size. A couple of years ago starlings ripped off the wire screen that covered the attic vents. They made a disgusting mess before I could get up there to fix it. Now they are dead on sight if I see them setting up shop around here. Don't like to kill things, but make an exception for starlings.