Window Strikes – A Serious Migration Problem for Passerines
Updated: Sep 6, 2019
The months of August, September and October are the time that song birds begin to fly south to warmer climates and more available food. Many song birds only fly to southern states like Arizona, others migrate to Central America and still others migrate deep into South America to the lowest parts of Argentina. The furthest south I have birded in the Western Hemisphere is the northeast quarter of Ecuador. I did that in February, 2016 and I saw many birds I was familiar with as summer breeders here in the Upper Clark Fork valley.
These annual migration cycles are fraught with danger for migrating birds and an estimated 12 to 15 percent die during migration. In order to make this voyage, they have to build up fat reserves and then often fly nonstop over mountain ranges or large bodies of water, such as the Gulf of Mexico. I have been in coastal Texas when storms were pushing winds south and migrating song birds were flying north. At such times, those that don’t perish from exhaustion in the head-winds, and fall into the sea, often barely make land fall. We once saw this phenomena, known as a “fall out” on the Texas coast. Birds were everywhere on the ground and trees seem to be dripping with exhausted birds barely able to move. It was quite an experience, and I saw great life birds, but it was at the expense of lactic acid laden flight muscles, which could no longer beat another stroke. At such times, many never recover and many more are lost without reaching land.
That kind of a fallout doesn’t happen locally, but migrating birds do appear in larger numbers when storms move north in September and October and birds are moving south. As they say, “There’s not much we can do about the weather”, but you can provide water, food and shelter in your yard for birds to “stage”, that is, rest, refuel, and gain the strength to continue south.
However, there is a danger in many yards and that is large windows that allow birds to think the window is a flight path or an escape route from predators such as Sharp-shinned Hawks.
We live in such a home. In part, we purchased our home because of its large windows and well-lit front room. We have a beautiful flower and bird garden that we enjoy immensely. In the photograph of one of our large windows you can see through the window and out another window on the other side of the house. A bird could easily decide this is a flight path and strike the window. Windows also reflect images and our bird garden is full of inviting foliage. Birds can mistakenly think the reflections are a place to purposely fly to for roosting and protection.
How serious are window strikes to migrating birds? Actual numbers are hard to determine. A 2014 study entitled, “Bird-building Collisions in the United States”, published in the Condor, an avian research journal, places the window mortalities between 365 million and 988 million annually in the United States. Fifty seven percent of the deaths were due to high and low rise commercial buildings. That leaves 43% of all bird mortality at residential structures like my home and yours! Do the math, window strikes at homes in America kill between 150 and 425 million birds annually! Fortunately, there is much we can do to reduce that number.
When we first moved into our current home three years ago and set out feeders, window strikes were often enough that we either had to do something to reduce the strikes or stop attracting birds to our yard.
If you do an internet search on stopping bird strikes, there are as many ideas as there are species of birds in Montana. Some solutions are simple; others costly. Some modify your windows very little and others nearly replace your windows with screens, nets, and ribbons. We have learned a little about reducing window strikes and yet let us enjoy our windows and the birds.
Based on our early experiences, I think our home would cause the mortality of 50 to 60 birds annually if we feed birds and did nothing to reduce window strikes. We have bird feeders stations on two sides of our home. Each station, has a black-sunflower tube feeder, a tube thistle feeder, a suet block feeder and water. Both feeder stations are close to vegetation that provides escape and protection away from the house. The west feeding station has far fewer widow strike mortalities than the east station. The reason, the west station is closer to the window. The closer the feeder is to the window, the less speed a bird can gain between the feeder and the window. A low impact strike may drop the bird to the ground, but they often recover. We are limited in how close our feeders are to the windows, as we have an eight foot wide porch. Birds are messy and we want the feeders beyond the porch, not on it.
What dynamically reduced window strikes for us were window decals. I use two decal types. The hawk pictured with this article is a solid silhouette and the dove is transparent silhouette. We prefer the transparent ones as they are more aesthetical pleasing to the eye and almost look like the image is etched into the glass.
A set of 15 of these can be purchased for under $20.00. Our windows are six by eight feet and 6 silhouettes per window prevents most window strikes. They work by either allowing the bird to know the window is there, or the hawk shape itself is a deterrent. Our silhouettes are not large, only four to six inches in size. They do not block our view and many folks have looked at them and thought they added to the pleasantness of our home.
Finally, during high migration periods, evidenced by the number of birds in your yard, we can lower insulated shades for short periods of time, totally eliminating the window from being a danger to birds.
Has our strategy completely eliminated window strikes and mortalities? No. So far this fall we have had three mortalities, one Northern Water Thrush, one Cedar Waxwing and a juvenile American Robin. Of course, three is too many, but far less than if we did nothing and fed birds.
So what do you do with birds that have died? They need not go to waste. College biology departments can use them in their ornithology classes to teach students bird identification and avian characteristics. You cannot legally have a dead migratory bird species in your possession. Through the Biology Department at Montana Tech of the University of Montana, under Dr Stella Capoccia, I have a salvage permit to collect and provide bird specimens to their collection for educational purposes. If you have a bird strike mortality in your yard contact me immediately, and I will collect the bird and give it to Montana Tech’s biology department. You can contact text me at 406-691-0368 or email me at email@example.com .
So this fall, don’t avoiding feeding birds and attracting them to your yard. Think about the placement of your feeders to protect birds, and purchase window silhouettes to reduce bird strikes. If you do experience a mortality, don’t waste the specimen. Donate it to Montana Tech so that future generation of students can learn the wonders of birds like you have.