I tried to get a picture of a fledgeling doing this Saturday, using a rain puddle, but she was too skittish and I could not get close enough with only my iphone for a camera. I'll keep trying though.
Until then, I found someone got movies of this and posted it on YouTube.
I'm jealous but 'til I can get my own movie of it, I'd rather you see it. Grackles in Houston have much longer tails than these.