More than likely that there area one small fish in that pond.

'Kingfishers feed on a wide variety of prey. They are most famous for hunting and eating fish, and some species do specialise in catching fish, but other species take crustaceans, frogs and other amphibians, annelid worms, molluscs, insects, spiders, centipedes, reptiles (including snakes), and even birds and mammals. Individual species may specialise in a few items or take a wide variety of prey, and for species with large global distributions, different populations may have different diets. Woodland and forest kingfishers take mainly insects, particularly grasshoppers, whereas the water kingfishers are more specialised in taking fish.

The red-backed kingfisher has been observed hammering into the mud nests of fairy martins to feed on their nestlings. Kingfishers usually hunt from an exposed perch; when a prey item is observed, the kingfisher swoops down to snatch it, then returns to the perch. Kingfishers of all three families beat larger prey on a perch to kill the prey and to dislodge or break protective spines and bones. Having beaten the prey, it is manipulated and then swallowed. Sometimes, a pellet of bones, scales, and other indigestible debris is coughed up. The shovel-billed kookaburra uses its massive, wide bill as a shovel to dig for worms in soft mud.'