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.

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Glass may appear reflective or transparent depending on conditions and time of day. Both scenarios invite birds to fly toward the building as they search for food and cover.
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Birds understand dark areas of glass to be passageways that they can fly through. The “passageway effect” is deadly for this reason.

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:

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