Imagine a beautiful field full of wildflowers, green trees, a bright blue sky, and buzzing with life. Sounds inviting, right? For a bird that vision is deadly – if it’s a reflection on a window. Window strikes are a major killer of our feathered friends. In a 2014 study, researchers estimated that up to 1 billion birds die each year from window strikes. At Wildlife Images it is the second leading cause of injury among our bird patients.
Many birds die on impact but even when a bird, momentarily stunned, flies off after a window collision, the rate of survival is extremely low. Just like with a human whose head slams against a window in a car crash, birds’ brains are traumatized. The swelling inside is often too much for the animal, or even rehabbers to overcome.
A recent patient at Wildlife Images’ clinic was likely the victim of a collision, although we can be positive what the bird crashed in to. The red-shouldered hawk patient arrived in excellent body condition. However, it was obvious that there was severe head trauma. The patient unfortunately died within 12 hours of arriving. The bird was in such good condition, other than the swelling in his brain, that it was a shame to lose him.
According to the Cornell Lab of Ornithology, there are two main types of window collisions: daytime & nighttime. In an article on the Lab’s website All About Birds it explains that “in daylight, birds crash into windows because they see reflections of vegetation or see through the glass to potted plants or vegetation on the other side. At night, nocturnal migrants (including most songbirds) crash because they fly into lighted windows. Some of these nighttime collisions are due to chance, but much more often the nocturnal migrants are lured to their deaths by the lights. For reasons not entirely understood, lights divert nocturnal migrants from their original path, especially in low-ceiling or foggy conditions. In the lighted area, they mill about, sometimes colliding with one another or the lighted structure.” Birds can also collide with windows because they see their reflection. Thinking it is another bird they go in to attack.
The odds are against them…
In the US, there is an estimated 1,027,720,000 (one billion twenty million seven hundred twenty thousand) windows in family homes (an average of 8 windows in 127.59 million homes). That’s not event counting business, schools, hospitals, or skyscrapers! To give birds a fighting chance against such staggering odds there are some things you can do. First, head outside to walk around your home. Make note of problem windows. Automatically anything with a bird feeder near it qualifies as do picture windows and windows at right angles. If you see a window that is reflecting branches, open sky…. or really, anything natural, a bird sees that too and it will be a window you need to bird-proof.
Wildlife Images suggests using a simple yellow highlighter to create a grid pattern on your windows. This will be virtually invisible to the human eye. Birds, however, are able to pick up the color variation and can then avoid the window. The birds’ size is important in how big to make your gird pattern. For song birds, go with a vertical line every 4 inches and horizontal lines 2 inches apart. If you are a mecca for hummingbirds than create a 2 inch by 2 inch grid.
The following ideas are from the Cornell Lab of Ornithology:
- Tempera paint or soap. Mark the outside of the window with soap or tempera paint, which is inexpensive and long lasting. You can use either a grid pattern no more than 4 inches by 2 inches (see above), or get creative and paint patterns or artwork on your window.
- Decals. Put decals, stickers, sun catchers, mylar strips, masking tape, or other objects (even sticky notes) on the outside surface of the window. These are only effective when spaced very closely (see above). Note that hawk silhouettes do little to deter birds. Remember: placing just one or two window stickers on a large window is not going to prevent collisions—they must cover most of the glass with the spaces between too narrow for birds to fly through.
- ABC BirdTape. This long-lasting tape offers an easier way to apply the correct spacing of dots across your window. More about ABC BirdTape.
- Acopian Bird Savers. Also known as “zen curtains,” these closely spaced ropes hang down over windows. They do the work of tape or decals but are easier to install and can be aesthetically pleasing. You can order them to fit your windows or make your own.
- Screens. Installing mosquito screens over your windows is very effective, as long as they are on the outside of the window and cover the entire surface.
- Netting. Cover the glass on the outside with netting at least 3 inches from the glass, taut enough to bounce birds off before they hit. Small-mesh netting (around 5/8″ or 1.6 cm) is best, so that birds don’t get their heads or bodies entangled but will bounce off unharmed. You can mount the netting on a frame, such as a storm-window frame, for easy installation and removal.
- One-way transparent film. Products such as Collidescape permit people on the inside to see out, but makes the window appear opaque on the outside.
If you’re building a new home or remodeling, the following ideas can also be good alternatives:
- Install external shutters and keep them closed when you’re not in the room or taking advantage of the light or view. (These can be huge energy savers, too!)
- Install external sun shades or awnings on windows, to block the reflection of sunlight. Remote controlled shades are available.
- On new construction or when putting in new windows, consider windows that have the screen on the entire outside of the glass.
- Add interior vertical blinds and keep the slats only half open.
- Avoid visual paths to sky and greenery. Bright windows on the opposite wall from your picture window may give the illusion of an open path to the other side. Closing a window shade or a door between rooms can sometimes solve this situation.