Night Flights: Why We Should Turn Out The Lights

Last year, on March 7th, 2025, 14 million birds flew over the United States. A profound number, yet a small percentage of the 3.5-4 billion winged beings that take to the wind each Spring and Fall, weaving together the airwaves and the planet. 

This is Bird migration. 

Each Spring and Fall, migratory birds, which make up 70% of terrestrial birds, travel between their wintering and non-wintering grounds. 80% of these billions of travelers take to the sky at night, navigating by the stars, the earth’s rhythms and magnetism, and casting silhouettes across the moon. They fly most frequently between 11PM and 3AM, when their gentle feet alight on the next stop towards their destination. 

Dr. Kyle Horton, Assistant Professor at Colorado State University in the Department of Fish, Wildlife, and Conservation Biology, shared with us that amid all the scientific facts he shares with his students, the aforementioned one is what most consistently and profoundly impacts them- the wondrous phenomenon that is millions of birds flying between us and the stars as we sleep. 

Together, Dr. Horton and I wondered what it is about these night migrations that inspires so many. We considered it might be the beautiful quality of mystery, how it adds layers to the avian story. That the red-headed, yellow-bodied Western Tanager at your feeder in the morning was up all night, traversing the infinite sky in his 1 oz feathered vessel. But, we know, too, that we cannot claim to know what it is that sparks the deepened appreciation in your heart. 

We can claim to know, unfortunately, that our feathered friends’ night journeys are under threat, with 2.5 billion migratory birds lost since 1970. A main cause of this devastation is the rampant existence of artificial lighting! From a charming lane with a single streetlight, to dense metropolitan areas, their luminance decreases the health of migratory bird populations. The light pollution over inhabited areas, otherwise known as skyglow, can both attract and disorient birds, which leads to an inability to reach their destination. The exhaustion from the extra expended energy can also make them more susceptible to threats such as predators  and window collisions- one of the leading causes of bird death. 

The good news is, we can take simple, poignant action to support the lives of migratory birds.

So, what can we do? 

Here in Colorado, we are part of the Central Flyway, one of four main migratory routes for birds in North America. In fact, on September 30th of 2024, approximately 25 million birds traveled across the state of Colorado between 11PM and 3AM. These birds, and birds around the globe, need our help and there are a variety of ways that we can give it. 

1. Turn off non-essential lights from 11PM-6AM during migration season. 

2. If indoor lights are needed at this time, install curtains that prevent light from emanating outside. 

3. Install shields on outdoor lighting that prevent light from emitting upwards into the sky. 

4. Install motion sensors wherever possible on outdoor lights so they illuminate only when necessary.

5. Advocate for businesses to turn out lights and for environmental laws to consider the health of migratory bird populations. 

6. When converting to new lighting, assess the quality and quantity of light needed and avoid over-lighting with newer, brighter technology.

While Snow Geese are already flying overhead in the hundreds of thousands, peak migration occurs from mid-March through June. This means that in about a month, we will once again be a part of one of life’s greatest spectacles. As we sleep, Birds will travel by the billions through starlit nights, braiding together the cycle of life as they go. 

You can join us in supporting their sacred journey in several different ways. First, you can get reminders to turn your lights out during peak migration by signing up for alerts here: https://aeroecolab.com/uslights. 

Second, you can stay updated on real time migration with Birdcast. Detected by the US weather surveillance radar network between sunset and sunrise, Birdcast and the Cornell Lab of Ornithology produce real-time analysis maps of nocturnal bird migration, as well as forecasts and predicitons, just like the weather.

Lastly, Denver Audubon partners with Lights Out Denver, whose initiative is- to increase awareness of migratory bird collisions with buildings in the City and County of Denver, and to promote practices that can help them. The program "collects data on bird strikes in downtown Denver during spring and fall migration to identify threats to migratory birds and to demonstrate the necessity of bird-friendly building regulations." Each spring and fall they need volunteers to paritcipate in data collection to help inform and create urban and migratory bird conservation efforts.

Birds consistently give us hope and we are finding that the more we look and listen to the world around us, so do people. People who take the time to turn out the lights, who spend their mornings engaging in community science, who work in policy. People like you, who marvel at migration with us and take intentional action to create a planet where this miracle flies long into the future.

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