They fly at night, over shopping centers and strip malls, parking lots, and airports. They fly over cities and highways studded with streetlights. They fly over nighttime high school football games, 24-hour gas stations, and office buildings that stay lit even after everyone has left. They fly through nights that seems black to us, but unnaturally bright to them.
They’re migrating birds. And all that light confuses them.
We can’t see these birds, but they fly above us, night after night through late summer and fall, in flocks so dense it can be picked up by weather radar.
According to the Pennsylvania Game Commission, more than five billion birds migrate across North America each fall. They head to where the warm weather is, flying south to Mexico, Central and South America, the Caribbean, or our southern states. Different species choose different destinations. These journeys cover thousands of miles and require enormous amounts of energy.
The birds navigate using the stars and the moon. The sheer amount of artificial light and the glow it creates on the horizon disorients the birds, distracting them from their migration path. Sometimes it causes them to crash into windows or buildings. Often they become caught in beams of light, and fly around aimlessly. This wastes valuable energy, and the birds become exhausted.
It’s estimated that millions of birds die this way, including some endangered hummingbirds, warblers, and thrushes. But it’s unnecessary and to a great extent, preventable. If homeowners and businesses reduce their light output in fall and spring, while birds are migrating, many of these deaths can be avoided.
Here are some suggestions from the Lights Out program sponsored by the Audubon Society:
During late summer though October, turn off outdoor lights and landscape lighting, especially flood lights. Use them only when absolutely necessary.
Turn off interior lights when practical, especially if you live in a house with many large windows or on the upper stories of a residential building.
If working late at the office, use task lights instead of overhead lighting, if you have the ability to do so. Or close blinds or curtains if your office has them.
When buying new outdoor lighting, choose fixtures with shades that cast the light down, not horizontally or up into the sky.
Write the elected officials in your area, or the managers of local buildings or your workplace, asking them to participate in the Lights Out program. You can find templates for letters here.
The BirdCast website has even more detailed information on light pollution and ways to reduce it.
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