Turning Off Home Lights Saves Birds? NO Scientific Justification
Dr. Jim Cubie Ornithology Center at Muhlenberg College
The Lights Out campaign urges homeowners to save birds by turning off a few home lights.
- Home lights – do not prevent collisions. There is no research showinig that lights cause bird deaths. All the research has been at large buildings with big lighted windows. The author of the key study has confirmed to me that his research does not apply to homes. On the otherr hand installing a bird collsion prevention system saves about 7 birds every year of about 100 over the 15 year life of a preventon sysem.
- Advice Fatally Flawed – If lights attraxt birds, and one home turns off its light, a bird will hit another home that does not turn them off.
- Overall Light Glow– Light emisisons from homes are infintesimal compared to the immense light a migration path is immense. The 250,000 street lights (alone) in the Chicago area emit 2,250,000,000 lumens. Note that is a “B”- billion. Add to that all the other lights in tens thousands of buildings. If a campaign convinces 1,000 bird lovers to turn off two (2) security lights, and they in turn convince a 1,000 of their neighbors to do the same, the lumen reduction is 0.0267% of the street lights alone.
- Lure and Confuse Birds The only research supporting this idea is at the 911 memorial lights. These huge lights are nothing like any home or any other building.
- Why Recommended? Membership organizations urge turning off home lights because they want their members and the public to feel involved in a lights out type effort. To protect insects, which are a crical part of a migrating bird’s food suppy. All outdoor lights should be controlled by motion sensors.
- Does No Harm — If a home only turns out lights, 100 birds will die in window collisions at a typical home and about 100 over next 15 years – 44% of all collisons are at homes. About 7 birds die hitting home widnows annually (7 X 115 = 105.) Installing a window collsion prevention system is easy and inexpensive. https://ornithologycenter.com/sdm_downloads/consumerguide/ Footnote 1.
Background This it is claimed, that turning off home lights will help save the “500 million to 1 billion birds killed by window collsions every year.” The phrase “turning off a few home lights can make a big difference” keeps showing up in outreach material. Since it defies common sense, I traced this quote, “turning off a few lights at home can make a big difference” all the way back to its source at Cornell Lab. When asked the question, “How could this be?” I was referred to the Van Doren paper. It is the only study showing that light management in a building can reduce window collision deaths. His text says that it applies to low rise buildings with large window spaces and with lights which are often on all night. It does not apply to homes, with a few lights on for few hours. I confirmed this in a phone call with him. (fn 1.)
If homeowners think that they can help birds by just turning off a light, why would they install a permanent system?
No outreach document should deliver the message that turning out home lights saves birds anymore than a doctor should tell his patient that exercise will cure his cancer. There is no scientific basis for either claim
I have urged the Lights Out campaigns to deliver this message: “while we are working hard to prevent bird collisions downtown, the best way for you to help is by installing bird window collision prevention in your home. About as many birds die hitting home windows as die hitting low-rise buildings.” A few local campaigns are delivering this message.
For information about these scientifically tested systems which protect against bird window collsions see the “Consumer Guide to Bird Window Strike Prevention.” FN. 3
Home lights should be off — or on motion detectors — all year, to save insects.
Wrong Information Causes Real Harm.
It may be said, “but it does no harm” if we tell people to turn off lights at their homes. That is wrong. It does cause harm. If you advise a friend that he use natural treatment for cancer, but he needs chemotherapy, your advice certainly harms him. He dies. It is the same if we advise people that they can save birds by turning out lights in homes. Birds die — thousands of them. These birds would have been saved if we had convinced homeowners to install permanent window collision prevention systems. If the Lights Out campaign convinced 100 homes to install bird window collision prevention, it would save between 73,000 – 99,000 birds over the next 10 years.
Home Lights Out – zero saved;
Permanent Installed Systems – 73,000-99,000 birds saved.
No ALAN Effect. It equally defies common sense that turning off a home light – even two thousand home lights – can have any effect on the over all light level above a city. In Chicago, there are 250,000 street lights and about as many again in the surrounding cities. The 250,000 street lights in Chicago emit 2,250,000,000 lumens. Note that is a “B”- billion. Add to that all the other lights in tens thousands of buildings. If a campaign convinces 1,000 bird lovers to turn off two (2) security lights, and they in turn convince a 1,000 of their neighbors to do the same, the lumen reduction is 0.0267% of the street lights. How many birds will be saved?
Footnote 1
Evidence, consequences, and angle of strike of bird–window collisions . Evidence, consequences, and angle of strike of bird–window collisionEvidence, consequences, and angle of strike of bird–window collisions. Daniel Klem, Jr.; The Wilson Journal of Ornithology (2024).
Footnote 2 Drivers of fatal bird collisions in an urban center; Benjamin M. Van Doren,1 , David E. Willard, Mary Hennen, Kyle G. Horton , Erica F. Stubera, Daniel Sheldond ,Ashwin H. Sivakumare , Julia Wanga, Andrew Farnsworth, and Benjamin M. Winger. PNAS 2021 Vol. 118 No. 24 e2101666118, https://doi.org/10.1073/pnas.2101666118
Footnote 3. For information about these scientifically tested systems see the “Consumer Guide to Bird Window Strike Prevention.” It includes a description of all the scientifically validated systems, compares prices, compares the effect on vision out the window of options and includes DIY directions for all.https://ornithologycenter.com/sdm_downloads/consumerguide/
Contact: Dr. Jim Cubie Ornithology Center at Muhlenberg College Jim Cubie1@gmail.com