Something says, "Great Blue Heron" to me too. I have Sandhills in my yard regularly and their droppings look somewhat different. I can't explain it but they just do. Maybe it is the Heron droppings look similar to the picture, especially the splatter. I also do not recall seeing a Crane relieving itself much past take off while I swear I've seen herons attempt to "bomb" boats as the birds flew by.
I wouldn't bet against the culprit being a crane but I'd suspect a heron first. They are a foul and mean bird.
