Would a great blue heron eat duck?

Yes, great blue herons do eat ducks. They are opportunistic predators that will eat a wide variety of prey, including fish, amphibians, reptiles, small mammals, and birds. Ducks are a common food source for great blue herons, especially during the nesting season when the herons need to provide a lot of food for their young. Great blue herons typically hunt by standing in shallow water and waiting for prey to come close. When they see prey, they will quickly strike with their long, sharp beak. Great blue herons are also known to hunt by flying over bodies of water and looking for prey from the air.