[Reading Science] Prevent 'Bird Strikes' in the Urban Area

The appearance of birds that died after colliding with building glass windows and roadside soundproof walls.
[Photo by Ministry of Environment website]

[Asia Economy Reporter Kim Jong-hwa] When birds collide with aircraft or get sucked into engines causing aviation accidents, it is called a "Bird Strike." In Korean, it is referred to as "Joryu Chungdol" (조류충돌).

Bird strikes mostly occur during takeoff and landing when the aircraft engines are operating at maximum power. This is because birds flying close to the low-flying aircraft get sucked in. Even a small bird weighing less than 1 kg can cause an impact equivalent to about 5 tons when it hits an aircraft flying at a speed of 370 km/h during takeoff or landing.

However, bird strikes are not accidents that only happen to aircraft flying in the sky. In urban areas, about 20,000 birds a day are killed by bird strikes when they collide with high-rise building windows and transparent soundproof walls.

The phenomenon of birds dying after hitting glass windows occurs worldwide. In the United States, up to 1 billion birds are killed annually, 25 million in Canada, and in Korea, it is estimated that about 8 million birds die each year due to urban bird strikes. This means about 20,000 birds die daily by colliding with glass windows.

Why do birds collide with transparent glass windows? Birds perceive glass windows as open space. Due to the transparency and reflectivity of glass, they do not realize it is a barrier and fly at their usual speed, resulting in collisions. The average flight speed of birds is about 36 to 72 km/h.

Usually, even a person riding a bicycle at top speed finds it difficult to exceed 30 km/h. As you know, birds’ skeletons are optimized for flight, with thin exteriors and hollow interiors, making them very vulnerable to impact. It is somewhat like the magpie in folklore that sacrifices itself by hitting a bell to repay a kindness.

Bird collisions can occur on glass windows of all buildings, whether in cities or rural areas. The total number of buildings nationwide is about 7.1 million. Even if only one bird collides per building annually, 7.1 million birds are sacrificed each year.

After glass windows, transparent soundproof walls pose the next greatest danger to birds. These soundproof walls, usually installed along roadsides, often cross bird habitats and are a more direct threat than building windows. Collisions occur even with very low single-tier soundproof walls, and endangered species, natural monuments, migratory and resident birds, regardless of season or time, frequently collide with these walls.

Recently, most urban soundproof walls are installed as transparent soundproof walls, and buildings decorated with glass facades are increasing, raising the risk of bird strikes.

To prevent the tragic deaths of birds, "Bird Saver" raptor stickers are sometimes attached to glass windows, but they are not very effective. This is because birds do not recognize fixed images as predators. However, birds generally avoid attempting to fly through gaps they cannot pass.

To prevent wild birds from colliding with glass windows, painting the exterior of the glass according to the 5x10 rule with paint or other materials helps birds recognize and avoid flying into it.
[Photo by Ministry of Environment website]

That gap is exactly a space 5 cm high and 10 cm wide. Using this characteristic of birds, experts devised the "5x10 rule" to save birds. By marking dots or lines about 8 mm in diameter at 5x10 cm intervals on building windows using paint or stickers, birds recognize that they cannot pass through and avoid flying into the glass.

However, the 5x10 rule must be applied on the exterior of buildings. If dots are applied indoors, they cannot block reflections of the outside scenery, so the effect is lost. For transparent soundproof walls, hanging strings thicker than 6 mm at 10 cm intervals or installing nets at an appropriate distance from the glass can reduce impact.

Countries such as the United States, Canada, and Switzerland have added bird collision prevention measures to building regulations and are promoting certification of collision prevention products and publishing guidelines. Although Korea cannot immediately implement such systems, campaigns are underway to reduce bird casualties. We hope to become a healthy city where humans and birds can coexist.