How Nature Interacts with Buildings

Many birds come in contact with Yale’s built environment—some in symbiosis, others in competition. From perching in oak trees that line Hillhouse Avenue to fluttering around buildings like the Health Center, birds are ubiquitous on our campus. While most birds that call campus home or visit during fall or spring migration safely interact with Yale’s buildings, collisions are not uncommon.

Buildings are one of the leading causes of bird deaths in the United States, with fatal collisions totaling over 300 million annually. Only cats rank higher, with an estimated 1.5  3 billion bird kills per year. Wind turbines, cell towers, and power lines contribute to far fewer bird deaths than buildings, with 573,000, 6.8 million, and 175 million annual bird deaths per year respectively.

Windows, which can number in the hundreds and even thousands for large buildings, are one of the main culprits of collisions. Because birds’ vision peaks in the ultraviolet part of the electromagnetic spectrum, and windows reflect visible light, birds often cannot see windows. As a result, they attempt to fly through and unfortunately collide with windows. Additionally, birds often mistake glass reflecting trees and shrubs for continuous space or habitat; they have difficulty distinguishing physical vegetation from reflections of vegetation. Birds’ tendencies to fly toward reflected light from windows is a result of their natural attraction to light sources for navigation.

Birds are also attracted to city lights. These light sources are another major contributor to bird mortality, as street and building lights can overwhelm birds’ visual sensors, diverting them from their migration paths. This can direct birds toward perilous collision zones.

Can we engineer the built environment in a way that supports the birds that come in contact with it? The US Green Building Council addressed this question by piloting a Leadership in Energy and Environmental Design (LEED) credit for bird-friendly design. The intent of the credit, designed by the American Bird Conservancy, is to “reduce bird injury and mortality from in-flight collisions with buildings.” 

The credit requires that buildings have window glass that is interrupted by visible patterns, shielded by screens, shutters, or louvers, or translucent with matte or textured surface to lower the collision threat potential of a building. Buildings must also adhere to specific interior and exterior lighting requirements. The credit calls for either shutoff by nighttime personnel or automatic shutoff for interior lighting, and either fixture shielding or adherence to another light pollution reduction credit. Exemptions exist for buildings that require 24-7 lighting for safety reasons. Many of Yale’s LEED credentialed professionals recently learned about these approaches when the American Bird Conservancy’s Christine Sheppard offered a seminar at Yale.

Other, innovative solutions are also surfacing, ranging from new technologies to repurposing arts and crafts supplies. Coated glass that reflects ultraviolet light is a new, effective strategy for reducing bird collisions. Applying stickers and tempura paint to windows is another solution that people are implementing, especially in personal homes.

Ultimately, what bird-friendly design comes down to is creating visual noise—physical elements in- and outside of buildings that birds can perceive. As Yale’s population grows and our campus expands, we must investigate how best to minimize our impact on birds and the urban ecology of our area.

“Knowing the extent and frequency of bird collisions can be extremely helpful in design and planning decisions,” said Jim Sirch, Coordinator of Public Education at the Peabody Museum and bird walk leader for Citizen Science. “Yale’s Central Campus, with its many shrubs and trees containing insects in spring and nuts and berries in summer and fall, provides important food and a rest stop for bird migrants, so understanding the effects of different building materials is sure to be a win-win for humans and birds.”

If you happen to find a dead bird, please record it on the YUBio Portal or here. If it appears to be freshly killed specimen, please consider donating it to the Yale Peabody Museum through Kristof Zyskowski, Ornithology Collections Manager.

To learn more, visit our website or attend a fall bird walk with Yale’s Citizen Science program.