Window Collisions Threaten Birds
Window collisions are a major threat to migratory birds and are the second highest contributor to bird mortality in Canada. Because windows aren’t perceived by birds, they can cause confusion by reflecting natural habitat or create sightlines to inaccessible habitat, which leads birds to fly into glass head-on. During the evening, light from windows can also confuse or attract birds towards glass. These collisions can cause immediate mortality, or cause disorientation and injury that can lead to eventual mortality.
The most dangerous windows for birds are large picture windows, those that are at right angles to each other, and windows that allow birds to see natural vegetation through the house.
Window collisions are of particular relevance in Vancouver, because the city is located on the Pacific Flyway, a migratory route for over 1 billion birds.
Solutions
Homeowners can take action to prevent collisions by treating windows to ensure they are bird friendly. Placing markers on the outside of glass is an effective way to make windows visible to birds. Markers should be at least 0.5 cm wide and placed no more than 5 cm apart across the entire area of the window. For a DIY alternative, draw designs on glass with tempera paint or oil-based paint pens. Exterior screens are also an effective deterrent.
It is also recommended that homeowners keep bird feeders within 1 m of windows. Window collisions are much more fatal when birds take off further away from glass and have time to reach peak speeds.
Municipal policy also plays an important role in keeping birds safe from collision and increasing awareness of effective window treatments. Help Vancouver become more bird friendly by advocating for a database of treated windows across the city.
