Bird collision with buildings in Sweden

Abstract

This thesis explores the escalating and often underestimated issue of bird-window collisions, specifically within the Swedish context, through the lens of the built environment. Globally, hundreds of millions of birds die annually from colliding with glass surfaces, with estimates reaching nearly a billion birds in North
America alone. This significant threat is compounded by modern architectural trends that increasingly incorporate expansive glazed facades and energy-efficient windows, which birds often fail to perceive as solid barriers due to their unique vision, mistaking reflections or transparent passages for open space. Despite the
alarming scale of this problem, particularly in Sweden where there are currently no specific requirements for bird protection in buildings and a lack of trained specialists, little has been done to prevent these collisions. The primary aim of this pilot study is to explore the problem of bird-window collisions in Sweden from a built environment perspective, understanding its scope within the Swedish context. The key objectives include determining the magnitude of bird-window collisions in Sweden, studying their specific context, and exploring current initiatives and solutions to address this issue. The methodology employed a multi-faceted approach, integrating insights from conservation organizations, historical data repositories, and the building industry. This involved identifying key information sources, establishing contact and gathering data, defining research questions, and synthesizing and analyzing the collected information. The findings confirm that bird window collisions represent a significant threat to avian populations in Sweden, aligning with global challenges and demanding urgent attention. National estimates suggest 16 million bird fatalities annually in
Sweden, a figure comparable to other significant human-caused avian mortalities. While citizen science data provides valuable qualitative insights, discrepancies with national extrapolations highlight the pervasive, often unobserved nature of these collisions. Key vulnerable species identified include the Greater Spotted
Woodpecker, Ring Dove, and Chaffinch, consistent across recent survey data and historical museum records dating back to 1974, underscoring the long-standing and broad geographical impact of the problem. The study clarifies the intricate relationship between collision risk factors, including the transparency and reflectivity of modern windows, architectural design choices and environmental factors. In conclusion, while the building industry is actively developing and offering technical solutions such as UV-enhancing coatings, patterned laminates, and surface-applied patterns, designed to make glass visible to birds, their effectiveness is critically dependent on appropriate design and spacing. A significant disconnect exists in current awareness and action in Sweden: conservation organizations are active, and the industry is innovating, but there is a notable lack of documented awareness and systematic monitoring at the local municipal level. This governance gap poses a substantial barrier to widespread implementation of effective bird-safe building practices. Future work should focus on political and policy implementation, as well as advancements in building engineering and architectural fronts to mitigate this critical issue.

Popular Abstract

Bird collision with buildings in Sweden.
Every year, millions of birds in Sweden die by flying into windows. What seems harmless to us is an invisible trap to them. To a bird, a glass facade may look like open sky or forest, or a clear passage to fly through. The result is often fatal resulting in stunned birds that never recover, or instant deaths hidden in gardens, on pavements, or at bus stops. Researchers estimate that up to 16 million birds are killed annually in Sweden by collisions with glass, numbers on par with those lost to cats.

Birds see the world differently than humans. Many species can detect ultraviolet light, and their wide vision fields are designed for flight, not for spotting invisible walls. Reflections of trees or skies in glass appear as real habitat, while transparent panes suggest an open route. Unlike people, birds cannot learn that windows are solid. Their instincts send them forward until it is too late, often resulting in brain injuries or broken bones.

The problem is not confined to high-rise buildings. In Sweden, collisions occur at homes, summer cottages, bus shelters, greenhouses, glass balconies and noise barriers. Records from the Swedish museum of natural history show cases dating back to the 1970s, proving the long-standing and widespread nature of the issue. Certain species are especially vulnerable, including the Greater Spotted Woodpecker, Ring Dove, and Chaffinch. Even rare species like the Kingfisher are affected. Collisions peak in spring and summer when young, inexperienced birds are learning to fly.

Birds are vital for ecosystems. They spread seeds, pollinate plants, control insect populations, and act as indicators of environmental health. Their decline threatens biodiversity and the natural services humans rely on. They are also part of Sweden’s cultural identity, from the blackbird chosen as the national bird to the familiar winter visitors at garden feeders. To lose millions each year to an invisible human-made hazard is both ecologically damaging and culturally sad.

The good news is that this tragedy is preventable. Conservationists and the building industry are developing ways to make glass visible to birds through UV coatings, patterned glass, Films, decals, and etchings that appear normal to humans but warn birds by breaking up reflections and reduce transparency. A surprising finding of this research is the lack of action by Swedish municipalities. While conservation groups are engaged and the glass industry is innovating, local governments rarely monitor or prioritize bird collisions. Without policies or building standards, bird-safe design remains optional rather than routine. This highlights a broader challenge: how to design cities that coexist with nature. Just as energy efficiency became a standard in architecture, bird safety could be integrated into building codes and urban planning. Sweden, with its reputation for environmental leadership, has an opportunity to lead in Europe on this issue.

Preventing the deaths of birds that bring life, beauty, and balance to our world from something as simple as glass is within reach. By rethinking how we design and live with our buildings, we can ensure that Sweden’s skies remain full of birdsong and not silence.

• author: Gupta, Jatin Sanjay
• supervisor: Pieter de Wilde
• organization: Division of Energy and Building Design
• course: AEBM01 20251
• year: 2025
• type: H2 - Master's Degree (Two Years)
• subject: Earth and Environmental Sciences
• keywords: Bird-window collisions, Biodiversity, Energy efficient windows, Bird Fatalities, Awareness, Monitoring, Policy Implementation, Building Design, Urban Planning, Sweden.
• language: English
• id: 9212794
• date added to LUP: 2025-09-22 12:56:05
• date last changed: 2025-09-22 12:56:05