by Lee Ann Landstrom, MRVAC Environmental Action and Education Chair

Best estimates are that between 365 million and one billion birds annually in the United States suffer strikes against windows and buildings. Birds do not see or understand glass, reflections, or transparency. If they see a reflection of trees, bushes – or even sky – they keep flying and smash into the glass. If the birds don’t die right away they often die after flying away.

What’s a homeowner to do? Disrupt the reflection. Here are some tactics.

I. Use window screens, whether part of the window system or added as an outer suspended layer. Interior blinds may be visible from the outside if the lighting is just right, but isn’t necessarily visible to birds. The Bird Screen Company sells hanging screen systems that are mounted outside your windows. See it at Easy Up Shades are made for solar shading, come in multiple colors and are mounted by suction cups. See them at

II. Hang things on the outside of the windows. Ropes, string, or ribbon close to the glass work. You can attach these to your window frame four inches apart or hang a rod (curtain-rod style) from which the ropes hang. Most people attach the ropes at the bottom, so they are not stationary and don’t flap around. Vertical ropes must be no more than four inches apart or horizontal ropes, two inches apart – commonly called the 2”x 4” rule. Small birds are agile flyers and will fly into narrow spaces. Experiments have shown that four inches or narrower gaps will stop most birds from flying through the perceived space.

Motion scares birds away. Some folks suspend lines of old CDs or DVDs to add an additional shiny deterrent. You can even suspend pie pans, Christmas decorations, aluminum foil strips, or flapping strips of plastic bags. Mylar balloons are shiny and flap around. (Don’t use helium, in case the balloon gets loose, flies far away and becomes a wildlife hazard.) You can suspend a branch across a large window to break up the reflection.

If you don’t want to make your own hanging ropes system, there are commercial ‘hanging curtains’ products available for purchase: Bird Crash Preventer is a monofilament fishing line system or Acopian BirdSavers’ “Zen Curtains” Another option is to stretch crop netting across the window. This is the most effective way to prevent bird strikes and deaths, albeit a bit unsightly. Birds hit the netting and bounce off. PolyNet comes in various lengths Woodpecker Netting is a three-quarter-inch mesh.  See it at

III. Treat the outside glass surface. Remember, putting things on the inside of the glass pane doesn’t disrupt the outside reflection. Temporary fixes can be fabricated from strips (one-eighth to one-half inch wide) of rainproof tempera paint, masking tape, rubbing lines of hard bar soap, even your own patterns made with florescent yellow highlighter markers.
More permanent treatments are commercial semi-transparent tape, U-V appliques (which come in various shapes) or vinyl decals that look like etched glass for an artistic flair.
Tape: ABC bird tape comes in three-quarter inch or three inch widths. See CollidEscape sells tapes in several styles. See

Prefabricated decals (must be spaced in the 2”x 4” rule). Bird’s Eye View Decals, which uses imbedded UV light, is placed on the inside of the window. See All Window Dressing, Etc. has dozens of small to large, even door, decals. See Window Alert decals reflect UV sunlight and come in several patterns. See Whispering Windows Anti-Collision Decals are white static clings in a half-dozen designs. See  The classic method of a hawk or owl silhouette is not effective. First, one silhouette in a large window does not address the four-inch rule. Second, birds tend to figure out that the silhouette is not real, or at the very least they acclimate to it. Often, folks stick these silhouettes on the inside of the glass, which doesn’t stop the reflection.

Films come in a variety of styles from many manufacturers. CollidEscape has several products; its original product looks ‘solid’ from the outside but thousands of small holes allow light in. See Solyx® Bird-Safety Window Films has several options at Feather Friendly® DIY is clear tape with little squares at appropriate distance. See

IV. Other tips.

  • If birds keep hitting your windows from bird feeders, move the feeder closer to your window or house. If they are scared off, they don’t have enough distance to build momentum and really hurt themselves. Recommended distance is 18 inches or closer.
  • Close curtains and blinds to break up the illusion of a clear passage or reflection, although time of day and amount of sunlight affect interior visibility.
  • If you have large plants close to a window, move them farther away. Birds might see these plants as a place to perch or hide.

V. Resources:

American Bird Conservancy at has great information for homeowners and architects, air tunnel tested and recommended products, and an extensive FAQ at Its Bird Collison Program tested various materials
Bird Watching magazine has several articles and reviews at Here’s a good summary article  Here’s the printable version:
There’s more information about building design and different types of treated glass. Check out the American Bird Conservancy website above. To see two different styles of bird-safe glass, visit the brand new Westwood Hills Nature Center, 8300 W. Franklin Ave., in St. Louis Park. The cover photo is a view from the outside: the lower level of glass is treated Ornilux, one of the least-visible products currently on the market that provides some significant bird deterrence via its ‘invisible’ grid of UV lines, while the upper layers are fritted glass that demonstrated the 2”x 4” rule.