Seattle Bird Collision Monitoring Project

Reflective Glass Building / Seattle Audubon

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

Click here to read the 2021-2022 Seattle Bird Collision Monitoring Project Summary Report

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. Migratory species, juvenile birds, and hummingbirds, appear to be particularly vulnerable to collisions. However, little research has been done examining the impacts of collisions in the Pacific Northwest.

The Seattle Bird Collision Monitoring Project seeks to document bird-window collision incidents 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

Seattle Bird Collision Monitors conduct daily surveys for dead and injured birds at pre-selected study buildings. Buildings are selected for design or other features that may contribute to or mitigate collision risk, including extensive glass facades, proximity to habitat, and more. In fall 2022, we monitored eleven buildings in the Capitol Hill neighborhood and on the University of Washington Campus every day for 45 days during fall migration.

Collision Monitors walk a specified route around the perimeter of each study building. If dead or injured birds are detected, the monitors record the location, condition, and description of the specimen, and collect the carcass for donation to the Burke Museum’s ornithology collection. If injured birds are detected, volunteers collect similar data and then make arrangements to transport the bird to the PAWS wildlife rehabilitation clinic.

Volunteer shifts recur weekly during monitoring seasons and can be completed in less than two hours.


Our Research Questions

What species are impacted by collisions in Seattle?

Patient intake records at the Progressive Animal Welfare Society (PAWS) show at least 84 speices have been treated for collision-related injuries. However, the PAWS data are limited, representing just those collision victims that were detected, survived, and transported to the PAWS facility. Our research seeks to flesh out our understanding of collision impacts on local and migratory species.

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?

Science for Conservation: Introducing the Seattle Bird Collision Monitoring Project | EarthCare Northwest Fall 2021

Volunteers started patrolling the streets of Seattle this month looking for dead birds. Their data generated from their efforts will help Seattle Audubon understand the bird-glass collision issue at a local level, and develop effective conservation solutions.