Imagine a fisherman pulling in his net after a long day at sea, only to find that birds have already taken a good share of the catch. It sounds almost absurd, until you realize it’s costing fishing operations real money, season after season.
Seabirds such as great cormorants and several species of gull are a real headache for fishers in coastal Europe who use large fixed traps known as pound nets. The traps funnel migrating fish into a sealed chamber, which fishers periodically drain. The same set-up that makes them efficient for fishing also makes them a free buffet for hungry birds sitting around.
Image Credits: Wikimedia Commons| For seabirds, a fishing trap is just a buffet with extra steps.
With several dozen birds constantly hanging around each trap, the economic losses for pound net owners add up quickly. The fishers tried to cover the traps with netting and build small hiding chambers for the fish, but neither had much success. Cormorants learned to swim underwater, and the hiding chambers actually increased the risk of birds getting tangled and drowning.
So researchers needed something different. Something humane, cheap, and smart enough to outsmart a bird.
Enter the giant eyes
So what do you do when the birds keep raiding your livelihood? Of course, you frighten them. But to do it humanely, without nets to drown them or guns to kill them, is tricky. That’s where a team of scientists in Denmark’s Western Baltic Sea came up with a wonderfully weird thing: a floating windmill with large pairs of eyes printed on its rotating wings. They named it the Looming-Eye Buoy, or LEB.
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Image Credits: Wikimedia Commons| A great cormorant flying with its breakfast.
It wasn’t an idea that came out of the blue. The LEB was originally created to reduce seabird bycatch in gillnets, where an estimated 400,000 seabirds are killed each year globally after diving into underwater fishing gear, according to a previous study published in Royal Society Open Science. In that earlier test, the device reduced the number of long-tailed ducks within 50 meters of the device by 20 to 30 percent. Buoyed by those results, researchers wondered if the same device might work above water, to keep fish-stealing birds away from pound net traps.
The idea was founded on animal psychology. The eyes would alter in size, bigger, then smaller, then bigger, as the wind spun the wings, simulating the visual effect of a predator bearing down on you. In theory, this would trigger a panic response, instinctive for a bird programmed to get away from approaching threats.They installed it near a pound net and watched what happened. The results, published in Royal Society Open Science, were very exciting initially.
Four days of glory
The difference was striking within 4 days of the LEB being placed. The site with the spinning-eye buoy had nearly four times as few birds as the control site without the buoy. Early numbers like that would have thrilled fishers in coastal US states grappling with double-crested cormorants, a similar species that has caused documented declines in bass populations across the Great Lakes.
But then gradually the birds began to come back.
Image Credits: Gildas Glemarec et al.| A cormorant perches steps away from the eye deterrent, unbothered.
Birds: 1, scientists: 0
Day 46, the last day of the trial, and the deterrent effect was gone. All the species that had been frightened away at first had gotten used to the buoy. The cormorants, gulls, and other birds had pretty much stared the giant eyes down and figured they weren’t a threat anymore.
This pattern is not unique to this experiment. Visual deterrents using eye-like stimuli have shown some early promise in reducing seabird foraging behavior, according to a study in Ecology and Evolution, but the core challenge remains habituation. Birds are smart enough to figure out that the scary-looking thing isn’t actually going to hurt them.
It’s a problem many American Midwest farmers, who use scarecrows, know well, as well as airports that use fake owls to keep birds off runways. The initial scare works, but it doesn’t last long.
Why it remains relevant
The failure of the LEB is not a dead end; it is useful data. Birds habituate in about a month, researchers know, which tells them exactly how long any single deterrent method buys you, and gives them a window to think about rotation strategies: swap out devices, combine visual cues with sounds, or move the buoys around frequently enough that birds never fully adjust.
The LEB idea, improved and combined with other strategies, may still be worth considering for US coastal fisheries and freshwater fish farms already suffering from cormorants from the Mississippi flyway to the Pacific Northwest. The question of how to protect fish from birds without harming either is not easily answered, but scientists are clearly willing to get creative, one set of giant googly eyes at a time.
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