Pond fish are always in danger of predatory birds. Birds can also pollute the pond water, spread algae growth and transport fish eggs from other ponds. If there is a dramatic loss of fish in the pond or the fish exhibit wounds such as puncture marks, a bird is likely stalking and consuming the fish. Most predatory birds are protected by the United States Migratory Bird Treaty Act and cannot be killed, so a pond should protected from birds using other means.
There are 90 species of kingfisher birds around the world, and all will readily dine on pond fish if presented with the opportunity. The kingfisher will dive for fish, scoop one from the pond and then vigorously beat the fish to death on a rock or tree before consuming it. If the pond is shallow and has a liner, the kingfisher's bills will easily rip and puncture the liner and cause the pond to leak. Bird netting can be stretched across the top of the pond to gibe the fish a little protection. Rock overhangs also allow the fish to swim out of the way of a diving bird.
Eagles do not focus on small ponds or tiny fish, but they will feast on larger fish in larger ponds or lakes. The eagle dives for its food quickly from above. There are several species of eagles, and all adore a fish dinner. Eagles also try to avoid human contact, so they usually stick with ponds that are not frequented often by human caretakers.
The double-crested cormorants (Phalacrocorax auritus) live inland and along the coastal waterways of the United States. The birds have become an extreme problem for fish hatcheries and fish ponds as their number increases, according to the Cornell Lab of Ornithology. The birds hunt pond fish by diving into the water. They will readily consume any fish species, but they have a special affinity for channel catfish. Many states report a catfish loss of 20 to 30 per cent because of the double-crested cormorants.
Great Blue Heron
The great blue heron (Ardea Herodias) fishes from pond banks or by wades into the pond to grab fish with its bill. The birds are known for being very persistent when it comes to finding a pond stocked with fish. They will traverse great distances to eat pond fish. They are excellent at finding even the most camouflaged pond. The birds do not require a great deal of space for flying and pond hunting, so even the smallest pond in a tiny backyard can easily be fished by the great blue heron. The birds are hard to scare away and not afraid of humans.