An active windshield wiper may not seem like a good place to perch, but this bird isn't choosy. That, or he's not going to let the humans push him off. -via Blame It on the Voices
I highly doubt that it's trapped. It landed on the windshield wiper out of it's own volition. Birds perch on branches (or wires) swinging in the wind all the time.
That's kinda sick. Bird could be trapped. I would shoo it away rather than risk dragging it by its claws across my windshield. Although, blood does wash out.
That would test the "he's trapped" theory.
With all due respect but I could think of worst examples.