From communication towers and tall buildings to residential windows and glass doors, birds face a multitude of dangers as they navigate our built environment. Research indicates that up to one billion birds may be killed per year in the United States alone as a result of collisions, happening in both commercial and residential settings, at all hours of the day. Surprisingly, the majority of these deadly collisions are occurring in low-rise buildings, rather than skyscrapers. The biggest hazards contributing to these collisions - artificial light at night and glass.
Some simple actions can help make our communities and the skies safer for birds.
Artificial lights and skyglow around buildings can be fatal to migrating birds at night, disorienting them or drawing them off course, leading them to circle in confusion and land in a vulnerable state. Lights may also attract birds to buildings and other structures. Considering these night-time hazards, here are some simple steps to help prevent collisions. Visit Lights Out to learn more about programs and activities underway focused on light and collisions.
- Reduce amount and intensity
Bright lighting can attract birds migrating at night, especially during periods of rain, fog, or low clouds, and cause them to collide with hard surfaces near the lights. Turn off or dim exterior lights, including decorative lighting and floodlights. Turn off internal lights or close shades, curtains, or blinds to prevent birds from seeing through windows and trying to fly through them. When converting to new lighting carefully assess quality and quantity of light needed, and avoid over-lighting with newer, brighter technology
- Change the direction
Lighting that is directed upward, such as search lights, can attract or disorient birds migrating at night. Direct exterior lighting downward or shield light fixtures to prevent light from spilling upward or creating a horizontal glare.
- Shorten the duration
Lights that remain on continuously attract birds migrating at night. Installing motion sensors for exterior or security lights will ensure they are only on when needed, reducing their ability to attract birds. For beacon lighting, switch to lights that blink continuously or continuously cycle on and off.
Birds don’t ‘see’ glass the way we do and may fly into windows and other surfaces that reflect the surrounding landscape or try to fly through glass that appears transparent and invisible. Birds need strong clues on or around glass to warn them that it’s there. To prevent these collisions, which can occur day and night, check out the approaches below. Visit our Reducing Collisions page for additional resources.
- Create patterns on the outer surface
Place dense patterns, such as stripes and dots, on the outer glass surface using commercial products designed for this purpose, or create your own design using craft paper, tape, stickers, paint, and markers designed to be used on glass.
- Make the glass appear opaque
Completely cover the outer glass surface with paint, perforated vinyl film, or other materials that will make the glass appear opaque. Perforated vinyl film products are available, which create a solid appearance from the outside, but allows views from the inside.
- Physical barriers
Place physical barriers like screens, netting, or hanging cords in front of the glass. As long as the physical barriers do not contain open spaces that are larger than 2 x 2 inches, or the hanging cords are spaced no wider than 4 inches apart, they can effectively discourage most birds from trying to fly through them into the glass.
- Close blinds or curtains
Blinds can help discourage birds from flying into windows by creating the appearance of a series of barriers. Closing curtains and shades can also discourage collisions on windows that appear transparent from the outside; however, they are best used on windows where collisions are being caused by the appearance of transparency.
- Move interior plants away from windows
Plants directly visible within windows and atria can be a danger as birds perceive them as habitat and may try to fly towards them.
- Place bird feeders directly on windows
Research has shown that feeders closer than three feet prevent birds from building up enough momentum to harm themselves if startled.
For examples of specific products and an illustration of these approaches, see bird-window collision prevention products and solutions, compiled by the Bird-window Collision Working Group (BCWG), a collaboration between The Acopian Center for Ornithology, Muhlenberg College, Lehigh Valley Audubon Society, Wyncote Audubon Society, and Audubon Mid-Atlantic.