Prevent Bird-Window Collisions

Hanging cords in front of windows (also known as Acopian BirdSavers, Zen Curtains, or Bird Crash Preventers) can be a highly effective and attractive way to reduce bird-window collisions. They can be made at home using simple, affordable materials.

To be most effective, follow these best practices when creating and installing hanging cords:

• Use durable, weather-resistant materials.
  Paracord, nylon, or polyester cords tend to hold up well in rain, sun, and wind. Cotton may degrade faster outdoors.
• Use cords that are at least ⅛ inch (0.125″) thick.
  Thinner cords may not be as visible, especially in low light or against reflective surfaces.
• Space cords no more than 4 inches apart.
  Wider spacing may look fine to us but can appear passable to birds, especially smaller species.
• Anchor cords securely at both the top and bottom if possible.
  While free-hanging cords are effective, anchoring the bottoms can prevent tangling in the wind and help maintain even spacing.
• Choose high-contrast colors.
  Dark-colored cords typically provide good visibility against reflective glass, but consider your window’s background—use a color that stands out from both the glass and the view behind it.
• Hang cords on the outside of the window.
  Just like decals, exterior placement ensures maximum visibility and reduces reflections that can confuse birds.

Learn more about and see photos of BirdSavers here.

Some types of architectural glass are specifically manufactured with bird safety in mind. These products often incorporate patterns, frits, or UV-reflective elements that are visible to birds while remaining subtle or nearly invisible to people. They are typically used in new construction or major renovations.

To maximize the effectiveness of bird-safe glass, keep these best practices in mind:

• Choose glass with patterns that follow the 2-inch rule.
  Just like decals, the markings or patterns in bird-safe glass should leave no more than two inches of space between elements.
• Opt for visible contrast when possible.
  Glass with high-contrast patterns (e.g., ceramic frits or etched designs) is more reliably effective across bird species and lighting conditions than UV-only options.
• Understand the limits of UV-reflective glass.
  Not all birds can see ultraviolet light, and UV reflectivity may be less visible during early morning hours when many collisions occur. If using UV-patterned glass (like Ornilux), combine it with other strategies where feasible.
• Extend treatment to all hazard-prone surfaces.
  Large expanses of glass, glass corners, and windows near vegetation or feeders should all be made bird-safe. Partial treatments can leave dangerous gaps.
• Consider bird-safe films as retrofits.
  If replacing glass isn’t possible, some manufacturers also offer adhesive films that mimic the patterns used in bird-safe glass and can be applied to existing windows.

Explore specialty glass options here.

Vegetation, including indoor plants, bird feeders, and bird baths bring birds close to our homes. If our windows are untreated, these bird attractants can increase the risk of bird-window collisions.

To reduce risk:

• Place bird feeders and bird baths very close to windows (within 3 feet). Collisions frequently happen when birds are scared off a feeder or bath by a predator. When feeders and baths are close to windows, birds don’t build up enough flight speed to injure themselves if they collide.

• Avoid placing feeders, baths, or dense vegetation directly in front of untreated windows. Birds may attempt to reach what they perceive as continuous habitat, especially if reflections show trees, shrubs, or sky.

• Use window treatments (e.g., decals, cords, or films) on all glass adjacent to feeders, baths, and habitat to break up reflections and help birds recognize the barrier.

• Trim or relocate indoor plants that are directly behind windows. From outside, they can look like part of the outdoor landscape and tempt birds to try flying through the glass to reach them.

Artificial light at night can attract and disorient migrating birds, drawing them into dangerous urban environments where glass poses a serious threat.

To reduce the risk:

• Turn off unnecessary lights at night, especially during spring and fall migration seasons.

• Use motion sensors, timers, and dimmers to reduce lighting while maintaining safety and visibility.

• Shield exterior lighting to direct it downward and minimize light spill into the sky.

• Close curtains or blinds at night to reduce interior light escaping through windows.

• Encourage participation in “lights out” campaigns in your building, workplace, or community.

Even small reductions in nighttime lighting can make a big difference, especially during peak migration weeks.

Take our Lights Out Pledge to receive resources for reducing artificial light at night.

If a bird hits a window at your home or office, report it at DBIRD.org, and online platform for reporting human-related bird mortality. Your DBIRD reports help scientists and conservationists document and understand bird-window collisions so they may prevent them.

Policy changes and building codes play a critical role in reducing bird collisions at scale. Advocating for bird-safe design helps ensure that glass hazards are addressed from the start.

You can help by:

• Urging local elected officials to adopt bird-safe building ordinances. Use our email template to send a message to your representatives right now.

• Encouraging architects, builders, and developers to incorporate bird-safe strategies into their designs.

• Spreading awareness among neighbors, property managers, and community groups.

Bird-safe design is often simple, cost-effective, and compatible with energy efficiency and other sustainability goals.