Project FeederWatch: Bird-Glass Collision Study

Many of us have witnessed the sad result of a bird flying into a window. A major source of bird injury and death involves bird-glass collisions, because birds do not see glass as a barrier. While collisions at large glass buildings have received lots of attention, scientists have identified that birds die from collisions with glass at smaller buildings and residences every year because of the magnitude of glass on smaller structures.

You can help us learn more about what impacts the danger of windows on smaller buildings, even if you haven’t observed any bird-glass collisions. Understanding the characteristics of glass windows and doors that do NOT pose a risk is as important as understanding factors that increase the risk of collisions.

Between February and April last year, FeederWatch participants were invited to participate in a Bird-Glass Collision Study that collected window information and collision reports. Almost 600 participants reported collisions and the absence of collisions on more than 2,500 windows.

We are continuing the study for the 2025–26 season, but this year we are extending the observation period through June, and we’ll be inviting participants to submit their observations each month. This year, we are hoping to gather more detailed information about various window treatments.

For the purpose of this study, “window” means any glass on the exterior of the building, including glass windows in doors and sliding glass doors. We’re asking participants to gather data on 1 to 5 windows at their FeederWatch count site, whether that site is a home, place of work, local nature center, or other location. After providing data about their windows, participants in this study will monitor for signs of bird-glass collisions and report information about any strikes they observe, or do not observe, on their selected focal windows. If you already have window treatments in place that are intended to limit bird-glass collisions, please do not remove them. We will ask you to provide information about them as well as information about any changes you might make to your windows over the course of the study. After collecting data from thousands of locations across the U.S. and Canada this winter and spring, researchers will analyze the information and generate recommendations for reducing the risk that glass poses to birds.

If you choose to participate, please keep reading to understand the data collection protocols. Thank you!

Video Tutorials:

Step-by-Step Instructions:

Step 1: Enroll in the Bird-Glass Collision Study

You must be a FeederWatch participant to participate in this study. We are sending all participants an email invitation to participate. Click the link in that email message to enroll in this study. If you have signed up for FeederWatch but haven’t received an invitation email, contact us. If you haven’t signed up for FeederWatch yet, join today!

Step 2: Download and/or Print This Tally Sheet

Step 3: Complete General Information

Using page 1 of the tally sheet above, fill in your ID number and the name of your FeederWatch count site. Please visit the My Counts page to find your ID number in the purple bar across the top of the screen. It is the number located to the right of your username. You can find the name of your count site on the home screen in the mobile app or by clicking the ‘Create, Edit, or Describe Your Count Site Location’ button on the My Counts page.

Next, record the approximate size of the entire focal building (square footage/meters of the entire building, including all floors). Note how many days in the average week you are able to detect window strikes at the location (e.g., days when you are present for at least two daylight hours). And finally, enter the date you will begin observing your windows for bird-glass collisions.

Step 4: Choose and Measure Your Focal Windows

Start by selecting up to 5 windows at your FeederWatch count site. For the purpose of this study, we are considering all glass on the exterior of the building a “window,” including sliding glass doors. The windows you select should:

• Include the window closest to your bird feeders (if you feed birds).
• Include any window(s) with which you know birds have collided in the past.
• Be in areas where you are likely to see or hear collisions if they occur. For instance, don’t choose a bedroom window if you are unlikely to detect any collisions in that area during daylight hours.

We suggest that you choose glass scattered around your focal building–the building where your count site is located.

Name each window for personal reference so that you remember which window is which throughout the study. For instance, you may choose to name windows “kitchen bay window” or “living room north window.”

Using the table on page 2 of the tally sheet, fill in information about your focal windows, including the dimensions of the glass and any features you have in place that might reduce bird-glass collisions. Estimated measurements are fine, just be sure to record in feet or meters using decimals, not fractions, inches or centimeters (e.g., record 4.5 feet to indicate 4 feet + 6 inches). If the window is facing any bird feeders (yours or your neighbor’s), then record the shortest distance from the window to the closest feeder.

Consider side-by-side or stacked windows as a single window if there is a 6-inch (15 cm) gap or less between the window panes (image on the left below). If the windows are separated by more than 6 inches (15 cm), then please consider those as different windows (image on the right below).

Step 5: Record Window Mitigations

Window mitigations are any method used to help prevent bird-glass collisions. For each of your focal windows, please note on the tally sheet all mitigations you are currently using. When submitting your observations online, some mitigation efforts may prompt you to indicate if they are inside or outside of your window and/or to select which of the images shown here best match your window (these images and descriptions will be displayed in data entry).

Types of mitigation:

• None: no mitigation strategy currently in place.
• Film: repeating patterns, either commercially available “bird film” or similar DIY patterns, such as window paint dots or stripes.

• Decals: individually placed shapes, either commercially available or DIY, such as hawk silhouettes, leaves, or other large shaped clings and paper cutouts.

• Strings: such as paracord, secured across the window.

• Screens: external to the window (interior screens are not applicable).
• Blinds/curtains: constantly drawn (closed) over the window’s interior surface.
• Objects: hung on interior glass surfaces or placed on ledges (including sun catchers, art pieces, or other objects, but excluding house plants).
• Other: Window features that do not match the above descriptions. (You will be asked to describe.)

Step 6: Submit Your Building and Window Information

After enrolling in this study, you should have received an instructional email message with a link to submit your building and window information online. Click the link in that message and enter the information you recorded in the first two pages of the tally sheet into the online form. Then submit the form.

Step 7: Record Any Bird-Glass Collision Observations You Make

Once you submit your building and window information, it’s time to start monitoring your windows. Use page 3 of the tally sheet to track your observations using your designated window ID letter from the table on page 1.

If you observe a collision, be sure to note the window involved and the date.

If you are able to identify the bird species, note that as well. Only record the bird species if you are confident of the identification; otherwise, please record ‘unknown’.

If you know the outcome for the bird(s) involved in a collision, please record one of these options:

• flew away immediately
• stunned and then flew
• died
• immediate predation (e.g., a hawk chased the bird and grabbed it following impact)
• other (please describe, there will be a write-in option on the online data form)
• unknown

Please record information about any bird-glass collisions that you detect on your focal windows at any time during the study (the collision does not have to occur during your FeederWatch count days). If you need more space, you can download additional copies of the tally sheet.

Step 8: Submit Your Window Observations

At the beginning of each month from January through early July, we will send you an email with a link to submit observations for the previous month. For example, January observations will be collected on March 1st, and so on. Please complete the data submission form each month you were able to observe your windows, no matter how few days you were able to observe.

Please report your observations even if you do not detect any bird-glass collisions! Knowing the features of windows that are NOT problematic is just as important as identifying features of problematic windows.

Questions?

If you have any questions, please email feederwatch@cornell.edu with “window study” in the subject line.