I have blogged about birds flying into buildings and windows before and the problem persists simply because there are more and more buildings and windows. It is especially severe during migration time in the northern hemisphere. Not only buildings and windows but power lines, towers, and wind turbines also pose dangers. Exacerbating the hazards from those sources is light, as in light pollution. Light pollution is a global issue. This became glaringly obvious when the World Atlas of Night Sky Brightness, a computer-generated online map based on thousands of satellite photos, was published in 2016, showing where our globe is lit up at night. Vast areas of North America, Europe, the Middle East, and Asia are glowing with light, while only the most remote regions (Siberia, the Sahara, and the Amazon) are in total darkness.
In 2022, World Migratory Bird Day was celebrated on May 14 with a theme of reducing the impacts of light pollution on migratory birds. The Migratory Bird Program of the Fish and Wildlife Service encourages everyone to reduce the impacts of light pollution. Artificial light is found almost everywhere across developed countries, and migrating birds are frequently attracted to lights, especially during inclement weather. Unfortunately, lights can cause confusion, disorientation, and exhaustion – directly impacting migratory behavior. Birds disoriented by lights can circle structures for extended periods of time, using energy stores critical for migration, or collide with buildings or windows. One unfortunate example is the light display on the 911 Memorial in NYC , every anniversary of the tragedy, that endangers thousands of birds. “Two beams of light–each with 44 xenon bulbs of 7,000 watts—rise into the night sky, mirroring the twin towers of the World Trade Center where nearly 3,000 lives were lost.” (All About Birds)
Many cities are directly in the path of migratory flyways. Migratory birds can also fly off course toward brightly illuminated cities. There are also other effects. A study of blackbirds (Turdus merula) in Germany found that traffic noise and artificial night lighting causes birds in the city to become active earlier than birds in natural areas—waking and singing as much as five hours sooner than their country equivalents. Fortunately, some communities are taking action to reduce their impacts. There are over two dozen “lights out” programs in cities around the country, and many are part of the Urban Bird Treaty Cities network.
We can all help, if only a bit. Turn off all exterior lights that are not absolutely needed and minimize inside lighting as well. Research has found that birds are particularly attracted to steady-burning red and white lights. Motion detector or times lighting may be an alternative. If you can’t turn off your indoor lights, closing your blinds or curtains will help.
Lights Out is a program of the National Audubon Society to help educate people to darken their homes and businesses at night during the migration season. Audubon also has a fact sheet providing information about making buildings bird-friendly.
A more scientific look at the problems of light pollution can be found in Nature: Scientific Report.