Innovative film for glass surfaces against bird strike

Large window fronts and high-rise buildings made of glass and steel suit our aesthetics, but are also a death trap for many (migratory) birds. In the USA, where intensive research has been carried out on this topic since the 1990s, it is estimated that around one billion birds die (per year) as a result of collisions with glass fronts. This is one of the world's biggest bird protection problems. There are already some solutions for glass fronts. A research team consisting of the Dresden Fraunhofer FEP Institute and JOANNEUM RESEARCH has now developed a film with a coating that is barely visible to the human eye, but very clearly visible to birds. This can prevent the impact.

Key facts

• Every year, billions of (migratory) birds die from collisions with glass fronts - in Germany the figure is around 100 million per year
• Birds cannot recognize glass
• Of the birds that collide with glass, 50 to 75 percent die, according to estimates from the USA
• 70 percent of collided birds die in the following days from internal or external injuries
• The larger and more reflective the glass surfaces are, the more dangerous they are for birds
• Free-standing glass walls or walkways with views - including those in bus and train waiting areas - are particularly dangerous for birds
• Corner glazing is also very problematic
• Vegetation behind the glass surface - such as in conservatories - drastically increases the risk of impact
• Illuminated glass fronts at bird migration times attract birds and lead to increased bird strikes

Bird strike threatens global bird populations

"The trend towards building with glass has made our gardens an often deadly environment for birds," says ornithologist Christa Glauser from BirdLife Switzerland.

"Collisions kill many birds that are already struggling with habitat loss, climate change, pesticides and so on," warns New York biologist Kaitlyn Parkins . "The problem is so easy to solve - you just have to replace the windows and turn off the lights."

Ornithologist Daniel Klem, one of the leading US researchers in this field, explains: "In terms of potential threat, I would put bird strikes right after habitat destruction. The insidious thing is that windows kill indiscriminately. They also hit the fittest members of a population. We can't afford to lose even a single specimen, but certainly not the ones with the best chance of having offspring." Klem considers window collisions to be one of the biggest problems in bird conservation.

"With the right markings on the outside of the glasses, the number of birds killed can be greatly reduced," says Christa Glauser, who has been working on the issue for years. She explains that conventional bird of prey silhouettes do not offer any protection. You need patterns with denser markings, stripes or dots, which are placed about a hand's width apart.

New film with ultraviolet pattern and nanocoating

As part of the EU project "Phabulous", the researchers combined several processes to develop the new film: nanoimprint lithography, coating technologies and plasma etching. This allows structures of different sizes to be produced. The dimensions range from a few nanometers to a few micrometers. The structures are therefore much finer than a human hair.

Dr. Matthias Fahland is pleased to explain: "We have achieved a particular success in the development of a new type of bird protection film. By equipping plastic films with micro-optical structures in a roll-to-roll process, we have achieved an optical appearance that differs significantly from that of unprocessed films. Application to glass façades makes it easier for birds to recognize the surfaces, thus avoiding collisions. The special feature here is that the contrast visible to humans is subtle, as the films differ most in the ultraviolet spectral range, to which the human eye is insensitive; birds, on the other hand, can clearly perceive the difference."

This ensures a reliable effect as a bird protection film in different light conditions. This new solution also offers advantages thanks to its almost full-surface transparency, which only has a minimal aesthetic impact on the architecture.