Seattle Bird Collision Monitoring Project

The Seattle Bird Collision Monitoring Project helps us understand and prevent bird window collisions.

Birds and Glass

Between 365 and 988 million birds die each year due to collisions with glass. That makes glass one of the greatest human-related impacts that directly kills birds. 

The Seattle Bird Collision Monitoring Project seeks to document bird-window collisions in Seattle, to identify factors that contribute to collision risk, and to support interventions that prevent collisions.

Hermit Thrush (collision victim) / Anne Freudenthal

How It Works

We follow a standardized collision monitoring survey protocol used by researchers around the world. During specified study periods, volunteers conduct daily surveys around pre-selected buildings for dead or injured birds. If any are detected, the volunteer records the location, species, body condition, and other details of the specimen. If the specimen is dead, the volunteer may collect the carcass for donation to the Burke Museum’s ornithology collection. If the specimen is injured, the voluneteer makes arrangements to transport the bird to the PAWS wildlife rehabilitation clinic.

Volunteers can participate by accepting a once-weekly shift to survey a set of study buildings along a route or by monitoring their own home. 

Our Research Questions

What species are impacted by collisions in Seattle?

Most bird-window collision research has occured east of the Mississipi and in Canada. The vulnerability of Western North American bird species to bird-window collisions is not fully understood.

How many birds strike study buildings per season?

Estimates of collision frequency can be a challenge to determine. Collision monitoring efforts typically result in undercounts due to:

• carcass removal from scavengers and humans, and
• imperfect detection of carcasses by surveyors.

Estimating the magnitude of these sources of bias is an important component of our research.

How do weather, season, and proximity to habitat affect collision risk?

Most research on bird window collisions has examined impacts on the East Coast, Midwest, and Canada. Species assemblages, migration patterns, and habitat conditions differ in Seattle and along the Pacific Flyway. Specific impacts, seasonality and other correlates of collision risk may differ here as well. For instance, a 2021 study from Vancouver, B.C. was the first to report the high vulnerability of the Varied Thrush to collisions in the Pacific Northwest, a species confined to western North America. The same study also found that collision risk during winter was as high as collision risk during spring. This has not been the case in studies in other geographies, where winter risk was low in winter compared to spring. The authors surmise that the abundance of conifers and other evergreen foliage in urban areas of the PNW may lure overwintering birds into proximity of structures where collision risk is higher.

What building design elements contribute to collisions?

The buildings we are studying have features that may contribute to collision risk, including extensive glass in facades, transparent balcony barriers, rooftop gardens, reflective glazing, and more. Some also have features that may mitigate risk, including exterior shades and awnings that reduce reflections. How do these design elements correlate with collision frequency? And how can we adapt our buildings to prevent deadly window collisions?