Collisions between birds and buildings are a common occurrence. The increasing anthropogenization of the environment, urbanization and the establishment of human settlements along the species' migration routes - are harming them. Glass facades, increasingly used in modern construction, pose a particular threat, as birds do not always see them - collisions occur even during the day.
Modern architecture relies heavily on the aesthetics of modern materials. One of the most distinctive elements of modern buildings are glass facades, which provide natural lighting, panoramic views and a visual connection to the surroundings. Glazed facades are valued not only for their aesthetics, but also for their functionality - they let in a lot of daylight, which allows for significant energy savings. Glass is also easy to maintain and provides good fire protection, which makes it often used in high-rise buildings, meeting the requirements for non-combustible materials. The modern use of glass elements in architecture is widespread, especially in large cities, where curtain walls often form the facades of modern buildings. The technique is associated with modern, dynamic, metropolitan character.
looking down
Glazing also has disadvantages. Unfortunately - what for us is an asset, for birds and other animals can be a death trap. Birds do not recognize transparent surfaces as barriers, which leads to numerous collisions, especially during periods of migration and breeding dispersal, when young birds are looking for new territories. Among the most important of the unwanted effects, further increasing the risk of collisions, are the mirror, transparency and beacon effects.
Anyone who has designed a glass building should walk by it at 5 a.m. and see the aftermath found on site.
The mirror effect can be found in a large percentage of modern office buildings where highly reflective glass curtain walls have been used. By reflecting the surrounding landscape, they give birds a false impression. Associated with this is the phenomenon of birds flying up and hitting the window panes. Seeing their own reflection in the glass, they treat it as an enemy with which they must compete and chase it out of their area. Such battles with their own reflection sometimes last for many minutes or even hours or days. As the authors of a compendium of knowledge on the subject report, "Birds unnecessarily waste time and energy that they should be using, for example, to get food or build a nest. They also risk being attacked by a predator."[1]
The effect of transparency can be particularly dangerous when objects potentially attractive to birds, such as tall vegetation, are located behind transparent glass. Not seeing the barrier of glass - they want to fly inside. Anyway - whoever has never absentmindedly entered a glass door, let him be the first to throw a stone.
In turn, the lighthouse effect poses the greatest threat to nocturnal species - the artificial lighting visible through the glass elements disorientates the birds, and collisions occur as a result of their loss of orientation in the area.
glass traps banned
Collisions with buildings pose a serious threat to birds, with serious injuries resulting in immediate death in about half of all cases[2]. It has been proven that between 365 million and 988 million birds die each year in the United States as a result of collisions with glass, in Canada the number is about 25 million per year, and in Germany up to 115 million. In Poland, the situation is similar[3].
At the legislative level, bird-friendly building design requirements are being introduced around the world. Toronto since 2010 has required new buildings to meet the Toronto Green Standard, which includes guidelines for "bird-friendlyglass." 85% of the lower part of the building (up to a height of 5 meters) must be made of this material. The requirements also apply to glass balconies and glazed roof areas. Toronto was the first city in North America to implement such restrictions. As of 2019, the Canadian Standards Association (CSA) has introduced a standard that sets out rules for bird-friendly building design. In 2021, New York City also set its own regulations.
The most important legal document regulating bird protection in the European Union is the Directive of the European Parliament and the Council[4] - known as the Birds Directive. The main goal of this Directive is to maintain (or adapt) the population of bird species at a level that meets ecological, scientific and cultural requirements. According to its provision, all species of birds naturally occurring in the wild in the European territory of member states are protected. In Poland, the law does not explicitly mention birds, but we can find provisions such as the Environmental Protection Law, or the Construction Law itself, which mandates environmental protection. The vast majority of birds in our country are under species protection. So if bird mortality is noticed, it is easy to refer to the provisions of the Law on Nature Protection[5] and the Law on Prevention and Remediation of Environmental Damage[6]. Proceedings related to environmental damage, and bird crashes are such, are carried out by the territorially competent regional directorates for environmental protection, operating in the territory of each province.
less push on the glass
The simplest solution to the problem of nighttime collisions is... turning off the lights in buildings. From mid-February to mid-May and August to mid-November, the most important migrations take place in Central Europe. It is during this period that it is recommended that lights be extinguished from 10 pm until sunrise, and where this is not possible, only well-focused light sources should be used. This problem simultaneously dovetails with the topic of light pollution.
However, collisions during the day are more difficult to avoid. Most bird collisions occur below a height of 5 meters, as this is the typical height of trees and other objects that birds use for landing, nesting and resting. Reflections cause birds not to see the glass, so signs must be placed on the surface to help birds notice them.
I'm making a controversial but much-needed thesis here - a glass building is not great at all. Let's stop teaching architecture students, proposing to investors and rendering big glass blocks for competition boards. At the design level, it's best to dispense with majestic glazing. The world economy won't collapse from this, and the city won't turn into Pompeii.
All visions of single-family houses, which are so beautifully supposed to integrate the surrounding nature into the living room, effectively kill the fauna living in the surroundings. Most collisions occur near areas with lush vegetation and high biodiversity. So just a huge window pane in such a place is the worst solution. When a collision results in the death of an adult bird actively involved in the reproduction process, the losses go further - they also include lost breeding opportunities.
Glass less contact, please
A key safety feature is the "hand rule." This is a rule of thumb for using the proper distance - about 5 by 10 centimeters, exactly the size of an average adult hand - that determines the maximum spacing between horizontal and vertical lines or patterns on the glass. Markers , in addition to having to have specific spacing, must also have proven technical parameters such as color, size or weather resistance, and must be placed on the outer surface of the glass. Markers can also be intriguing - those used during the Kresge College expansion at the University of California, Santa Cruz, depict animals in the local ecosystem.
Bird-friendly glazing also includes etched glass. The use of frosted, sintered, patterned glass or glass blocks is also helpful. There are already dedicated glazing in this form. As designers, remember that where we can use marked glass, it should preferably be interspersed with opaque, frosted glass.
Another way to protect birds from glare from glass is to use UV coating - transparent to humans, but visible to birds in the UV spectrum. It is also important to use anti-reflective glass, which reduces the reflection of visible light and provides high transparency. Glass with an external reflectance of no more than 15% is a good choice. When anti-reflective glass is used on corners, corridors or connectors, additional protection is needed using any glass treatment techniques.
In addition, it can be helpful for birds to use facade blinds, and in traditional, historic buildings - shutters, which will also protect against overheating of the building. Blinds are only a partial solution - we use them mainly on sunny days and certain hours, which amounts to less protective effectiveness. Also mosquito nets are able to protect birds from collision. Regardless of the type of design, they allow the window to open freely and effectively protect birds from impacts by cushioning the force of a potential collision. As reported by the already mentioned Glass Traps Foundation, in order to fulfill their protective function, they should be installed at least 5 cm from the glass[7].
with a view to the future
The realization of full protection of a building's glass facade can be a difficult task to achieve. For this reason, the American Bird Conservancy advocates taking immediate, accessible action, even if it doesn't eliminate the problem entirely. According to ABC, it is better to take practical steps now than to wait for ideal solutions that may never come. By using the technologies mentioned, it is possible to design buildings that will be safer for birds, minimizing the risk of collisions.
Although birds are the most common victims of collisions with glazing, other animals are also affected by this problem. Bats, which use echolocation, can be disoriented by smooth glass surfaces. Even large mammals, can hit glass barriers without being aware of their presence. Architecture has a huge impact on the world around us, and glazing in buildings is a prime example.
As architects, we have a moral obligation to design buildings that are not only beautiful and functional, but also environmentally friendly. With conscious design and the use of appropriate technologies, we can create an environment that is safe for both people and animals.
Magdalena Milert
[1] Zyśk-Gorczyńska, E., Mikusek, R., Sztwiertnia, H., Adamczyk, M., Aleksiejczuk, A., Gołębiowska, A.,.... & Zbyryt, A. (2021). Bird collisions with transparent surfaces: a compendium of knowledge. Glass Traps Foundation.
[2] Oglęcki, P., & Żabicka, J. M. (2023). Mortality of birds as a result of collisions with glazing on the example of building structures in Warsaw. Zeszyty Naukowe SGSP/Szkoła Główna Służby Pożarniczej, (85).
[3] Gleń, Z., Gołda, M., Koba, P., & Bełkot, Z. Collisions of birds with transparent surfaces. Selected issues in environmental protection and hazards, 52.
[4] 2009/147/EC of 30 November 2009 on the Conservation of Wild Birds (EU OJ 2010 No. 20, item 7), https://eur-lex.europa.eu/legal-content/PL/TXT/?uri=celex%3A32009L0147
[5] https://isap.sejm.gov.pl/isap.nsf/DocDetails.xsp?id=wdu20040920880 and its implementing act: § 6 of the Decree of the Minister of Environment of December 16, 2016 on the protection of animal species.
[6] https://isap.sejm.gov.pl/isap.nsf/DocDetails.xsp?id=wdu20070750493
[7] Zyśk-Gorczyńska, E., Mikusek, R., Sztwiertnia, H., Adamczyk, M., Aleksiejczuk, A., Gołębiowska, A.,. & Zbyryt, A. (2021). Bird collisions with transparent surfaces: a compendium of knowledge. Glass Traps Foundation
