Why do birds collide with windows?
For birds, glass windows are deadly. During the day, windows reflect the foliage of nearby vegetation. During the night, artificial lights can attract and disorient birds. Glass is a novel material to birds; they are often unable to perceive and avoid clear or reflective glass barriers. Many birds die immediately upon colliding with a window, or become stunned and fly away, later dying from internal bleeding or bruising. The U.S. Fish and Wildlife Service has found that most birds collide with low-rise buildings (i.e. one to three stories tall, <80ft in height) and that these collisions account for between 500 million to 1 billion bird deaths annually (2). 

How can we prevent bird collisions with windows?
There are a variety of glass and window design options that can be integrated into building designs before and after construction. The goal of these alternatives is to create visual signals and cues to help the birds detect and avoid glass. Many glass samples tested by the American Bird Conservancy have greatly reduced the number of bird collisions when used to replace or retrofit glass with a high number of bird collisions.

The University of Illinois should adopt bird-safe window standards

We know that bird collisions are actively occurring on our campus. From data collected by undergraduate and graduate students, we have found over 450 total dead birds that have collided with campus buildings during two three week survey periods in the fall of 2019 and 2020. The majority of these birds have been found during migration seasons. For most of these birds, the University of Illinois is in the middle of their migratory path. To avoid future bird mortalities, we petition the following to the University of Illinois System Board of Trustees:

We request that the University comply with the “Building façade and site structures,” “Exterior lighting,” and “Performance monitoring plan” requirements that are outlined in the LEED Green Building Rating System Pilot Credit 55: Bird Collision Deterrence. The code also highlights guidelines for “All other structures on the site, including, but not limited to handrails, guardrails, windscreens, noise barriers, gazebos, pool safety fencing, bus shelters, band shells, etc.” which must adhere to a particular set of materials that when used decrease the chances of bird collisions. The intent of this building code is to reduce bird injury and mortality from in-flight collisions with buildings. These changes will help ensure that current and future buildings on campus are designed to minimize bird collisions.  

Proposed building policy changes

1. New Buildings Bird-friendly glass used for windows ≤ 80ft from the ground Bird-friendly glass: Glass with a threat factor of 30 or less as tested by the American Bird Conservancy or assigned by the Bird Safe Building Alliance. The lower the threat factor, the more effective the collision reduction. There are many options, including glass (e.g., frit, etch, ultraviolet), screens, double-skin façades, and more. No more than 15 ft2 of non-bird-friendly glass can be used in any location unless it is covered by screens, double-skin façades, or similar materials that obscure a direct path to the glass window.
2. Retrofitting existing buildings to be bird-friendly For deadly glass where the preferred retrofit cannot be installed immediately, install inexpensive solutions that can be removed when the preferred retrofit is ready (e.g., Acopian Bird Savers, Bird Tape, Feather Friendly’s Do-It-Yourself – see www.birdsmartglass.org) to immediately save birds. These are also excellent long-term options and after they are installed the campus may decide they like the look and leave them in place, which will likely save money.

1. Rosenberg K V., Dokter AM, Blancher PJ, et al. Decline of the North American avifauna. Science (80- ) 2019; 366: 120–124.
2. Loss SRSS, Will T, Loss SRSS, et al. Bird–building collisions in the United States: Estimates of annual mortality and species vulnerability. Condor 2014; 116: 8–23.

Photo: Champaign, IL, Alec Luro