It already comes in black, so all I had to do was form it into beak shapes and sort of mold it around the faces of the crows so the beak would stick properly.While not the most perfect sculpting job ever, I did manage to turn out some serviceable beaks. A dab of hot glue, and ta-da! Beaks! While I was at it, I touched up the faded feathers of the crows with black fabric paint. Much better!
I keep reminding myself that they will be seen from a distance, and at night. For those purposes, I think they look fine.