Patterns embedded, applied or painted on glass greatly reduce bird collisions if they meet the following requirements set out by FLAP Canada, the American Bird Conservancy and most bird-safe design guidelines.
1
DENSITY
Maximum 5 x 5 cm spacing between pattern elements to prevent small birds from trying to fly between the markers.* The pattern must be applied to the entire window.
2
EXTERIOR SURFACE
Window markers must be on the outside of the glass in order to break up reflections.
3
SIZE
Individual pattern elements must be at least 6 mm wide.*
4
CONTRAST
Patterns must be visible in all light conditions.
* Differences between North American and European pattern recommendations
Both European and North American recommendations specify high-contrast markers applied to the exterior surface of the glass. The advice regarding marker width and spacing is more complicated due to differences in the methods use to evaluate bird-safe products,
A testing method developed in Austria considers the minimum spacing, size and contrast of glass markings independently of each other. This approach leads to more nuanced recommendations that cannot be explained in terms as simple as the North American rules for glass markings.
Based on these tests, less dense patterns with up to 9 cm of space measured horizontally and 5 cm vertically, using markers measuring at least 9 mm wide, as illustrated below, may be sufficiently effective in areas where there are no species as small as hummingbirds.
However, it is unknown of this spacing is sufficiently dense to prevent other small Eurasian species, such as Goldcrests and Firecrests, from colliding.
For more information on bird-safe patterns tested in Europe, download “Bird-friendly building with glass and light” (3rd edition. Swiss Ornithological Institute in Sempach, 2023).
For more information on bird-safe patterns tested in North America, download “50 Bird-friendly Glass Patterns” (American Bird Conservancy, 2023).
An expert can help you determine which solution is most appropriate for your project.