Birds, like humans, can not see glass. Collisions with glass on buildings and on homes is a leading cause of bird mortality, second only to habitat loss. Current estimates place the annual losses at 1 billion per year. Birds have evolved to navigate their environment at flight speed, making quick decisions, and perceive glass reflection, transparency, and passageways as open sky.


We want a front row seat to nature, to observe and be part of the natural world even when we are inside. What we don’t want is a front row seat to the violent thud that will claim a healthy bird during prime breeding condition or a fledgling attempting it’s first migration. Rethinking glass and utilizing it’s incredible properties while making it safe for birds is possible. To help birds see the invisible threat we can:
- provide visual cues to birds to alert them to the presence of glass: ABC Suggestions
- take steps at home, especially during migration periods, to modify windows
- learn about the 2×4 rule and why it saves birds
When designing a home or building:
- Avoid over-use of glass – keeping glass to less than 40% of the overall surface area has a positive effect on bird mortality
- Use a smaller pane size – glass panes with less that 2.5 square meters inherently create grid line patterns that are sometimes visible to birds reducing risk of collision
- Use non-reflective glass options – opaque, etched, and patterned glass create a natural visible barrier for birds
- These must be applied in the first 2-3 stories of the building where reflectivity of surrounding environs is the greatest concern
- Any pattern must be no more than 4″ wide by 2″ tall to provide the necessary visual barrier
- UV patterned glass and fritted glass (with ceramic dots, lines, and patterns) provide visual cues to birds without a substantial impact to the view for humans
- Architectural features can also provide the necessary visual barrier to prevent collisions:
- Overhangs and balconies designed into the building provide a visual cue to birds
- Shutters, louvers, mesh, awnings, and films can be added post construction
- Landscaping in the immediate vicinity of glass can provide an area for birds to alight, slowing down their speed and preventing impacts