By Julia Schimmelpenningh
Thanks to the pioneering work of dedicated scientists, ornithologists, wildlife associations, and the glass industry, the future is looking brighter for the billions of birds which end up colliding with windows each year. While still in its infancy, the science of bird-safe glazing is emerging with creative new ideas and changing the way birds see and react to building glass. Similar to the evolution in hurricane-resistant glazing, which began several decades ago, the road to developing adequate bird-friendly codes, local ordinances, and glass testing is evolving. For specifiers tasked with selecting bird-friendly glazing, this article provides an overview of current glass testing options and other information to help when designing a beautiful yet bird-friendly building.
How big is the problem?
Birds are essential to the ecosystem. They consume vast quantities of insects and control rodent populations, further reducing damage to crops and forests and limiting the transmission of diseases such as the West Nile virus, dengue fever, and malaria. Birds also regenerate habitats by pollinating plants and dispersing seeds.
With the increase in glass as a design medium, bird collisions into architectural fixtures and buildings have also increased, and awareness of this has become a chief driver for bird-friendly guidelines and regulations. Technical improvements and performance capabilities have made glass more accessible and desirable for architects; however, its transmissive and reflective nature, although beautiful to humans, can confuse birds.
Birds cannot distinguish the presence of glass in architecture, so they attempt to fly through it. If the glass is reflective, it can present an oasis effect by somewhat mirroring the surrounding vegetation and environment, drawing birds into a reflection of the world around them which is not real.
Glass on lower levels, closest to the ground, and adjacent to “green” patios and balconies can reflect vegetation or landscapes, posing just as much risk for bird strikes as upper-level glass reflecting clear skies or providing seemingly pass-through corridors for flying. Birds attempt to reach habitats, open spaces, or other attractive features visible through or on glass surfaces.
Birds use their eyesight to orient themselves, but most birds have eyes on the sides of their heads. This allows them to see sideways at a wide angle, giving them a view of any approaching enemies or mates from all directions. The disadvantage, however, is their spatial vision is severely limited, and they have difficulty recognizing obstacles in fast flight. Birds in flight may only see the landscape behind the pane of glass and fly against it unchecked.
Beyond tall buildings
While the blame for bird collisions is often concentrated on tall buildings, skyscrapers are only part of the equation. According to a report on glass collisions, “Most collisions take place during the day, and almost half occur at home windows; low-rise buildings account for almost all the rest.”1
Tall buildings, buildings with green balconies and rooftops, and wide buildings with large expanses of glass also cause enough bird collisions to make bird-friendly glazing a priority for all levels of architecture, from suburban homes to urban skyscrapers.
Dangerous migration flyways
Bird migration patterns occur worldwide, with eight major migratory pathways through the Pacific Americas, Central Americas, Atlantic Americas, East Atlantic, Black Sea-Mediterranean, East Asia-East Africa, Central Asia, and East Asia-Australia. However, even without these migratory paths, birds residing in the same location all year are just as much at risk of glass collisions.
Typically, birds’ encounters with glass are fatal, as they have weak skeletal systems and the impact at full flight can be crushing. Birds tend to collide with glass at high speeds and their small bodies, composed of hollow bones, leave them vulnerable to injury or usually, a fatality. Healthy and mature birds are just as likely to collide with windows as young, vulnerable ones.
