Meaning of a dead starling at your door?

It means you have a bird-killing cat, or that the bird was not watching where he was flying, or that the bird suffered from some fatal illness (birds do become ill, just as people do). In the wild, birds often die or are killed, and then, other species will eat them. Occasionally, they die in a surprising (to us) place such as a lawn or a front step. And there is no mystical or supernatural meaning to a dead bird on your front stoop.