Seagull droppings cause roof damage: Laser beam used as a deterrent

28. februar kl. 16:09
Seagull droppings cause roof damage: Laser beam used as a deterrent
Green laser beams seem to be effective in scaring away the large flocks of seagulls that cause damage to the roof of the fishing terminal in Hirtshals. Illustration: Malene Møller Madsen.
Every year, seagulls leave up to 10 tonnes of droppings and dirt on the roof of Hirtshals fishing terminal. This eats away at the roofing felt. Neither robotic lawnmowers, kites, plastic foxes nor plastic owls have been able to scare them away. But laser beams now appear to be effective.
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In Hirtshals, large flocks of seagulls have been causing problems for the town’s fishing terminal for years. Normally, roofing can last at least 30 years, but the birds leave around ten tonnes of droppings, nests, feathers, food leftovers the roof every year, and the mixture of droppings and dirt corrodes the roofing felt, so the roofing has to be replaced much more often than usual. This is explained by the operations manager at the Port of Hirtshals, Palle Boelt Andersen, in an email to BuildingTech.

“The roof is approximately 17 years old, and we have begun with the first stage of the replacement of roofing felt. If we were to do it again, we would have started with the replacement two years ago, because the roof is now damaged after the drain has been clogged too many times due to seagulls’ droppings/waste.”

To reduce the problem, he has to send a team to the roof every year with brooms, shovels, and wheelbarrows to remove the dirt, but this cleaning, like the sun’s UV rays and the local climate, causes significant wear to the roof.

The fishing terminal in Hirtshals houses both a fish auction and a fish crate washer. Combined with its location next to the sea, the building’s 7,000 m2 roof is an attractive landing spot for thousands of seagulls. Illustration: Styrelsen for Dataforsyning og Infrastruktur.

The fishing terminal in Hirtshals houses both a fishing auction and a crate washer. Combined with its location next to the sea, the building’s 7,000 m2 roof is an attractive landing spot for thousands of seagulls. But their droppings damage the roof. Laser beams now seem to be effective in keeping the birds away.

Robotic lawnmowers, kites, and plastic foxes and owls

Therefore, over the years, there were various attempts to scare the seagulls away.

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According to Nordjyske and TV2 Nord, which have covered the problems, both kites and plastic figures of owls and foxes have been placed on the roof. But the birds quickly get used to them, and then they return. There was also an attempt to use a robotic lawnmower to patrol the roof, but this did not work because the robot would lose the signal due to the cables in the terminal’s drop ceiling.

Now, however, the fishing terminal has begun using a new weapon that so far appears to be effective: laser beams.

Stressed out by laser beams

Through the Norwegian company Vestflow, the fishing terminal has purchased a system consisting of a “laser cannon” mounted on a motor unit that can turn the laser in different directions.

“The laser is currently running a preset path consisting of 32 points, which are manually determined through the camera that somewhat resembles a regular surveillance camera. One can decide what the path should contain—edge delineation, etc.—and the laser stops at each point for five seconds before continuing. This should also be upgraded in the future with a new type of camera that can run 200 preset points,” Palle Boelt Andersen explains in the email.

Operations manager Palle Boelt Andersen and his colleagues have tried plastic foxes, plastic owls, kites, and even robotic lawnmowers to scare the seagulls away. But without luck. The new “laser cannon” on the roof of the fishing terminal, on the other hand, shows promise. Illustration: Malene Møller Madsen.

Since the 1970s, similar types of lasers have been used in airports (including Aalborg Airport), in agriculture, around aquaculture, and on buildings in other countries. The effectiveness has been tested by researchers on several occasions—for example by a Dutch research team that in 2021 demonstrated that lasers reduced the visits of wild birds around a free-range chicken farm by 98.2 percent.

Green light perceived as solid objects

The explanation behind the lasers’ efficiency is that birds perceive light in the green spectrum as physical objects. So when the green spot sweeps across the roof, the birds feel as if something is approaching them, and this makes them flee. According to Vestflow, the effect is even greater at dawn and dusk, when the laser can illuminate dust and water particles in the air. In those situations, the entire laser beam appears to the birds as a solid rod moving across the roof.

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In Hirtshals, however, the laser has had to be upgraded to increase efficiency, Palle Boelt Andersen says.

“We started out with a smaller 600 mW laser diode. It was barely visible across the whole roof. Subsequently, we have changed the laser diode to a somewhat more powerful 800 mW laser diode. That one is functional and visible. The manufacturer is working on getting us a 1000 mW laser diode—hopefully before the summer holidays.”

On its website, Vestflow also describes 1000 mW lasers as the ideal solution in places with a lot of sun and where seagulls present a problem.

Effectively annoys seagulls

But even with the 800 mW laser diode, Palle Boelt Andersen already sees a good effect.

“There is probably a blind spot where it doesn’t hit. But where it does, it just works. The laser beam travels both horizontally and vertically around the clock, and it rests for five seconds at every point it reaches. The seagulls can’t figure it out, and the light is very annoying for them,” he explained to Nordjyske.

Still unsure about the cost efficiency

Palle Boelt Andersen cannot yet say with certainty whether the purchase of the “laser cannon”, which the locals have already given the name Mågens, is overall a good and cost-efficient solution.

“We don’t know much about its lifespan yet. It’s used in a harbour environment that is tough on all types of material. We hope the maintenance will be minimal—perhaps a new diode every two years? The acquisition cost is approximately DKK 60,000, and there is also some IT help required for programming.”

Equally decisive will be whether the seagulls will get used to the laser beams. Palle Boelt Andersen obviously hopes that the effect will last.

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“We can see that it works, and we hope that it continues to do so, but seagulls are good at getting used to things,” he says to TV2 Nord.

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