This is pure conjecture, but here goes. Barred Owls are known to consume small mammals, birds, reptiles, amphibians, fish and invertebrates. I have repeatedly encountered a Barred Owl lately near a pool of water in a brook that has all but dried up. Fish have become trapped in this pool due to the dryness of the summer, and are easy pickings for predators. Even though studies have shown that fish are a very small percentage of a Barred Owl’s diet (2.5% in owls from New Jersey, New York and Connecticut during the breeding season), I am betting that the owl that I flushed yesterday that was perched right next to the isolated pool in the brook was spending the day (and night?) at his favorite fishing hole. Three times it took off from its perch as I approached, but only flew a few feet away each time. Perhaps fish or frogs kept it from disappearing further into the woods.
Common Mergansers are primarily fish-eating ducks. Young mergansers require over half a pound of food per day during their first summer, and often supplement their fish diet with insects, mollusks, crustaceans, worms, frogs, small mammals, birds and plants. The pictured immature Common Merganser had just downed a crayfish when it spotted a frog which it succeeded in catching and eventually swallowing.