The fact that Ducks eat bugs is not new – the quacking waterfowl consume beetles, grasshoppers, locusts, and many other insects.
While it is uncommon, ducks can eat cicadas in the same way they eat many other bugs. The crunchiness and the unique taste of cicadas make them a good treat for ducks.
Generally, cicadas are not poisonous, so they are unlikely to cause any toxicity to ducks. Besides, ducks are omnivores...
Ducks should not eat too many cicadas. If they consume too many cicadas at a go, they may become too full to eat their primary diet.