How to Choose Glass that Prevents Birds from Colliding with Buildings

Written by Antonia Piñeiro
Published on June 02, 2020

Did you know that World Migratory Bird Day is celebrated in the second week of May?

Every year around this date, festivals, educational events, exhibitions, and excursions are organized to celebrate and raise awareness about the conservation of migratory birds. These species have seen their habitats transformed during the last few decades in part because of human action: designers and real estate agents have built and nurtured an urban imaginary dominated by glass structures as a symbol of power and progress. Before proceeding with the conquest of the sky, it is worth considering some materials that are more friendly to the species with which we cohabitate.

Millions of birds die each year from collision

The problem is very simple: birds cannot see glass as a solid object, but only recognize what is reflected in it. Whether it is a tree or a piece of the sky, they do not identify the obstacle as a danger and as a result collide with it, with the risk of dying. Academics estimate that, in the United States alone, between 100 million and one billion birds die yearly, while in Canada, the number is around 25 million. Although specific data is difficult to obtain, it is clear that the migration period is the most dangerous for the birds, as they find themselves in front of tall buildings in unknown territories.

From mid-rise buildings to skyscrapers, the structures we create can become a death trap for hundreds of bird species around the world. Since 1970, more than three billion birds have disappeared in the north of the American continent, due, among other things, to the transformation and urbanization of their habitats (the most affected territories being forests and coastal areas). Although parks, forests, and gardens may be spaces committed to species conservation at the urban level, these deaths are often preventable through simple design decisions and choosing the right products.

What options are there to fight this problem?

Glass being the main problem, it is possible to find variants in the market that make it easier for birds to identify a glazed surface, including options that make it visible to them without distorting what humans see.

Transparent Alternatives

One of the options is to add a coating to the glass that reflects ultraviolet light, which will be practically invisible to humans but always visible to birds. The technology is incorporated into the laminated glass in a sheet, almost imperceptible to the human eye in dry conditions.

Some specialists also consider photovoltaic glass a bird-friendly option. This type of glass contains cells that accumulate energy to generate electricity, which is incorporated onto the glass in a photovoltaic sheet by means of electronic printing. Different levels of transparency can be obtained, including fully transparent options that are compatible with films that reflect ultraviolet light. However, it is important to consider that bird nests and other interferences can negatively impact the glass' ability to generate energy.

Translucent Alternatives

There are numerous techniques for incorporating visible patterns into glass. One such solution is ceramic printing. Depending on the supplier, you can choose colors, regulate the opacity of the ink, and opt for decorative patterns. Advances in technology for screen printing on glass (silk-screening) allow for varied decoration styles superior to traditional engraving techniques (etched glass). Today, ceramic printing on glass offers both the possibility of silk-screening a design using a template (the oldest form of glass printing still in use) or doing it by digital printing, which is more flexible than silk-screening. The choice between the two methods is usually based on considerations such as location, quantity, image, sustainability, and function, though they may also be used as complementary techniques.

Impresión cerámica sobre vidrio. Image Cortesía de Dip-Tech

If the designer and client are open to glass that is not fully transparent, there are two additional options: dichroic glass and translucent glass. Dichroic glass is multi-colored, produced by stacking and alternating layers of glass along with micro-layers of quartz glass and metal oxides to achieve the appearance of changing colors by transmitting and reflecting light, like a kaleidoscope. Translucent glass can either be channel or fritted glass, and is porous and opaque, produced by subjecting the glass to thermal melting. In some cases, it can have a load-bearing capacity and be designed in curved or textured forms.

Whichever option you choose, the design of the pattern to be incorporated into the glass is of paramount importance. A study by Dip-Tech, endorsed by the American Bird Conservancy, has shown that patterns with randomly arranged triangles are more effective than homogeneous colored dots or stripes. The golden rule is to follow a "2x4" inch spacing: the marks are to be added on the plane with a spacing of two inches horizontally and four inches vertically. Birds tend to avoid gaps of these dimensions, so a stricter "2x2" rule will ensure the inclusion of smaller species.

Cities that have incorporated this concern into their regulations have defined a range of solutions. In the case of San Francisco, 90% of glazed buildings over 18 metres adhere to these regulations. According to Dip-Tech, and contrary to what one might think, the collision zone is not the highest area of the building, but rather the floors the birds hit when they fly down to rest. Although there are still not enough regulations and the vast majority are in North America, there are also certifications in countries without these regulations that recognize this type of initiative and help suppliers certify their products.

Are there other solutions?

There are other lower priority factors such as lighting and window design that can contribute to the solution for this problem. The window frame can be an ally in making the façade more identifiable, while artificial light disorients the birds and causes them to collide with objects. Adding temporary solutions such as curtains, plants, or accessories are also an option. However, solutions that are sustainable over time must be incorporated from the beginning of the design process.

Although most of the information and institutions in charge of this problem are in North America, birds connect the world through migration. Concern about this phenomenon is not only a problem of respect for the environment, but also reflects that the increase of biodiversity is necessary for our own survival: birds are pollinating agents, distribute seeds, and control insect pests. Now is as good a time as ever to question the conventional use of materials and to pay attention to their negative consequences. If you are designing a glazed project, consider these solutions before October, the date of the second annual migration.