Birds and Windows

Every year a billion birds are killed by collisions with building window glass. While most fatal collisions happen at homes and buildings shorter than four stories tall, smaller structures like glass walkways and bus stop shelters also pose a threat. Fortunately, there are ways we can prevent this leading threat and make a big difference for the birds!

Birds do not see glass as a barrier to avoid. When they are attracted to landscaping or interior lights and see natural reflections (like clouds and trees) in the glass or plants through windows, they often fly into the glass without realizing it is there. Sadly, many birds that seem fine following such collisions later die from injuries.Windows that reflect the sky and trees around them or that are very transparent can confuse birds, causing them to see a clear flight path rather than an obstruction.

These collisions are preventable, and there are ways you can make your homes and buildings safer for birds.

Prevent collisions by placing feeders either more than 30 feet (10 meters) from a window or closer than 3 feet, (one meter). A feeder that is 30 feet or more from a window is a safe distance from confusing reflections, while one within 3 feet prevents a bird from building up enough momentum for a fatal collision. 

Dress Up Your Windows
Patterns can be applied to the outside of windows to help birds see that glass is there. These patterns should be ¼-inch in diameter (or larger) and be placed no more than 2 inches apart from each other. Spacing patterns in a 2" x 2" grid is especially important for protecting small birds like hummingbirds. Dark colored patterns can be difficult for birds to see when the window reflects dark colors, so it can be best to use medium to light colors for visibility.

Parachute cord: This elegant, inexpensive option uses 1/8-inch paracord pieces spaced less than 4 inches apart, hanging outside from the top of the window. The paracord creates a visual barrier for birds. These curtains can be purchased pre-made or constructed of readily available and inexpensive materials.

Tempera paint: Using the 2" x 2" spacing mentioned above, non-toxic tempura paint patterns or artwork applied to exterior glass can reduce bird collisions for many years. Tempura paint is easily removed using vinegar and water. This can be a fun activity to do with family, friends or even in a class with students!

Screens and netting: External insect screens reduce bird collisions by reducing window reflections and alerting birds that windows are barriers. Netting prevents injuries to birds if the bird can safely bounce off the screen instead of hit the hard glass. Net openings should be 1/2-inch or smaller, so birds don’t become caught. Screens can be attached with suction cups or eyehooks.

Tape, decals, and external films:  Products are available in many colors, tints, and patterns.

Choose Bird Friendly Glass
Acid-etched, Fritted or Frosted Glass
Most effective when on the glass exterior, “fritted” glass includes adhered ceramic lines, dots or other patterns. Etching, fritting, and frosting not only reduce the risk of bird collisions but also reduce energy costs by reducing solar heat gain (27 SHGC) and reducing cooling loads. You can save energy and birds while still naturally lighting your buildings. Existing glass can be frosted using sandblasting. The American Bird Conservancy provides the latest recommendations in glass products and techniques.

Ultraviolet Patterned Glass
Ultraviolet (UV)-reflecting glass products are available with patterns generally invisible to humans but visible to many birds species. The American Bird Conservancy provides the latest recommendations in glass products.

Channel Glass
Patterns created by channel glass reduce bird collisions and is made of energy efficient, recycled materials. The American Bird Conservancy provides the latest recommendations in glass products.

Reduce Lights at Night
Lastly, one of the simplest actions we can take has less to do with the glass and more to do with our lights! Though birds collide with glass all throughout the year, it happens the most when they are on the move during spring and fall migration. Most birds migrate at night, making them more vulnerable to buildings and other structures lit with artificial lights they might be attracted to, often resulting in tragic collisions, entrapment, and exhaustion.

Minimizing artificial lights at night can make a big difference for birds, pollinators, and even us humans who like to see the starry night sky! Turning off unneeded lights by hand or using timers and motion sensors can not only lessen bird attraction to glass, but can also reduce energy costs and light pollution overall. Using blinds, shades, awnings and shutters in windows can also reduce the amount of light that escapes in or out and help birds see the glass as a barrier.