Blue herons are majestic birds that can often be found around ponds and other bodies of water. However, their presence can cause problems for koi owners, as blue herons love to eat fish! Koi are particularly vulnerable to predation from herons and other birds due to their bright colors and tendency to swim near the water’s surface. If you’ve noticed your prized koi disappearing lately, a hungry heron may very well be the culprit. The good news is that there are several effective techniques you can use to deter blue herons and keep your koi safe.
Why Do Blue Herons Eat Koi?
Blue herons are opportunistic feeders that eat a variety of small fish, amphibians, insects, and rodents. Here are some of the main reasons why blue herons target koi ponds:
- Easy meals – Koi swim close to the surface and their bright colors make them easy for herons to spot.
- Stocked food source – Ponds provide a convenient source of many fish gathered in one place.
- Koi lack cover – Unlike natural ponds and lakes, koi ponds usually lack places for fish to hide from aerial predators.
- No threat from koi – Unlike some native predatory fish, docile koi won’t fight back against or disturb feeding herons.
Overall, koi ponds represent an irresistible feeding ground for hungry blue herons in search of an easy meal.
How Much Damage Can Blue Herons Do?
A single blue heron can wreak havoc on a koi pond very quickly. These large birds can consume several fish per day. Some key facts about the impact herons can have include:
- Herons may return day after day until all fish are gone.
- Loss of expensive koi – Show-quality koi can be worth hundreds or even thousands of dollars apiece!
- Increased algae growth – Loss of fish allows algae growth to spike without their grazing.
- Introduction of disease – Herons can introduce diseases or parasites into a pond by moving between bodies of water.
Left unchecked, a persistent heron can completely depopulate a koi pond at a great financial and emotional cost to the owner. Taking action as soon as a heron shows interest is crucial.
Physical Barriers to Exclude Herons
The most direct way to stop heron predation is excluding the birds physically from accessing your pond. Some options include:
Pond Covers
Covering the entire pond with netting or mesh is very effective at keeping herons out. The material must be sturdy enough that herons can’t puncture it. Allow for some slack so the cover doesn’t dip below the water’s surface. Incorporate structural support like PVC pipe frames. Covers can impact oxygen exchange at the water’s surface, so additional aeration may be needed. Openable covers offer the ability to enclose or access the pond as needed.
Fencing
Fences around the perimeter of a pond can also deter herons, which do not like to take off from a confined space. Fences should be at least six feet tall and made from materials a heron cannot easily grip or climb like wrought iron, aluminum, or PVC. Place fence posts very close together (less than 2 inches) so herons cannot slip between them. Sloping the fence inwards also helps deter perching.
Wires
Wires strung tightly across the pond’s surface prevent herons from landing. Use steel wires or monofilament fishing lines. Space lines no more than 5-6 inches apart for best results. The entire pond surface should be crisscrossed for full coverage. Combine with a perimeter fence to stop herons from poking through the wires from shore.
Fish Shelters
Providing covered shelters at the bottom of the pond that koi can swim into for safety will help reduce predation. Make sure shelters have openings only large enough for koi to swim through. Use materials like PVC tubing or cement drainage pipes propped up on cinderblocks. Give koi enough shelters to all be able to use them when herons are present.
Heron Deterrent Systems
There are a variety of devices available that scare or startle herons to train them to avoid your pond. These should be used in combination with exclusion methods for best results:
Motion-Activated Sprinklers
These sprinkler systems detect heron movement and shoot quick bursts of water to scare them away. Place sprinklers positioned to cover key areas herons frequent around the pond. The intermittent stimulation keeps herons startled.
Predator Decoys
Lifelike decoy predators like owls, hawks, snakes, or alligators placed around the pond area can help deter herons. Change decoy locations periodically so herons don’t become accustomed to them. Motion-activated decoys that suddenly move or make sound are especially frightening.
Noise & Ultrasound Devices
Noisemakers, ultrasonic devices, or recorded distress calls randomly activate to startle herons. Mix up sounds and timing patterns frequently so herons don’t become desensitized. Use several devices around the pond for better coverage.
Other Deterrent Options
Some other tactics to make your pond less appealing include:
- Installing a bubbler fountain for constant water movement.
- Partially submerging plastic alligator heads.
- Running a radio constantly near the pond.
- Using flashing laser lights or disco balls.
- Applying non-toxic water treatment dyes or spray-on films to reduce water clarity.
Varying combinations of techniques simultaneously makes it harder for herons to become accustomed. Just be sure deterrents don’t also negatively impact your koi. Maintaining good water quality and reducing fish stress also helps prevent disease outbreaks in the wake of any heron attacks.
Scare Away Herons Actively
When herons are actually present, you can take direct action to scare them away and teach them not to return. Some options include:
- Running at them waving your arms and yelling.
- Blowing loud whistles or air horns.
- Squirting them with water guns or hoses.
- Throwing objects like small pebbles near them (not directly at birds!).
Any action you take must not physically harm the herons to comply with law. Be persistent and consistent during every intrusion to effectively modify heron behavior over time. Enlist family members to help with active hazing efforts.
Call Local Wildlife Officials
If heron predation is ongoing despite deterrents, contact wildlife officials in your state for additional guidance. They may be able to refer you to licensed trappers who can live-capture persistent herons and relocate them away from your pond location. Simply moving a problem heron is generally more effective than lethally removing it.
Properly Fence Off Nearby Nesting Areas
If the herons visiting your pond are nesting nearby, excluding them from their nest site may help resolve the issue. Contact wildlife officials to determine proper nest exclusion methods. Note that nests with eggs or young are protected from any disturbance during nesting season. Prevent exclusion attempts until chicks fully fledge.
Stock Pond with Native Predator Fish
Adding small native predatory fish like bass, bluegill or catfish that eat young herons and other birds can make a pond less appealing. However, predatory fish also consume koi, so this option doesn’t work well in dedicated koi ponds. It may help reduce heron and egret issues in ponds with mixed populations of ornamental and native fish.
Train a Heron-Specific Dog
Some dog breeds can be trained to patrol pond edges and chase herons on command. Border collies and other intelligent, high-energy breeds tend to excel at this task. Hire a professional dog trainer to ensure your dog responds properly only to herons and does not harm other wildlife or pets. Train the dog to approach but not contact herons.
Apply for Damage Control Permit
In extreme cases, it may be possible to apply for a damage control permit through your state wildlife agency to destroy a problematic heron. These permits are only granted if the heron is causing significant recurring damage that cannot be resolved by any other means. All non-lethal options should be thoroughly attempted and documented before applying for lethal control.
Find Alternate Koi Pond Location
If heron issues ultimately cannot be managed at your current pond site, stocking a pond in a different location may be required. Seek out sites farther from natural waterways and wetlands where heron activity is lower. Completely indoor ponds in greenhouses are essentially heron-proof. This solution should only be a last resort after exhausting all other options.
Conclusion
Persistence and creativity are key in outsmarting problematic blue herons. Combining physical exclusion devices, scare deterrents, and active hazing is most effective. Seek expert advice if substantial losses continue despite multiple control efforts on your part. With some diligent effort, you can successfully safeguard your prized koi while allowing blue herons to utilize more appropriate feeding habitats elsewhere.
