The Gateway Arch in St. Louis is going dark for bird migration all September long. But this is just a start; below are some tips for how you can help at home.

Why St. Louis?

St. Louis sits along the Mississippi Flyway, a corridor used by about 40% of the nation's migratory waterfowl, which makes the city's glow especially costly. Birds often mistake the glow of the arch for a celestial object, becoming confused and disoriented.

The National Park Service has been doing this every spring and fall since 2002, and it has helped save millions of birds.

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Why birds migrate at night

About 80% of birds migrate overnight. After all, flying takes a lot of work, especially when they keep going for hours. Birds may be little meteorologists because they know that those cooler nights are helpful for maintaining body temperatures.

Also, conditions tend to be calmer in the overnight hours as the daytime heat can create more unstable air.

Birds also prefer migrating at night because they can use celestial objects that are largely stationary in the sky, like stars, for guidance. And there are also fewer predators awake and active in the overnight hours.

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What you can do at home

It's not only on the National Park Service to protect migrating birds. You can help, too.

The goal is to reduce as much light pollution in the middle of the night, especially during the peak migration periods for birds, which are mainly in May and September.

Here are some things you can do.

Turn off all nonessential exterior lights between 11 p.m. and 6 a.m.: We all enjoy leaving the porch light on overnight for peace of mind. But this month, let's try to keep it to a minimum.

Close blinds at night: Closing blinds prevents light from spilling out, further reducing light pollution.

Point outdoor light fixtures down: Doing this prevents excess light in the sky and also helps birds to not confuse these lights with stars in the sky.

Replace bright white LEDs with warm-color LEDs: I hated being in classrooms with bright white LEDs, and birds don't seem to enjoy them either. An excess of LED lights in a city draw birds into the urban area can cause collisions with buildings.

Install motion sensor lights instead of always-on lights: Motion sensor lights are not only a good way to save on the electricity bill, but they can also help reduce light pollution.

Birds will thank you

Human impacts can make it very difficult for birds to make this perilous journey. Light pollution from cities, buildings and residential areas can draw birds in for miles. They then approach and circle the lighted area. Eventually, they tire out and can become confused, potentially running into buildings or homes.

Studies have come out in recent years showing that nearly a billion birds die every year due to collisions with buildings and homes.

But the situation is changing.

The results are coming in, and this is making a huge difference. In Chicago’s McCormick Place, they noticed a drop in mortality by 59% when they turned off lights during peak migration months.

A separate study noticed that in Philadelphia, when they turned off the lights in these peak months, collisions of birds decreased at one site by 70%.