Threats to Birds: Collisions (Nighttime Lighting)

Protecting our Night Skies for Birds

Impacts of light pollution on migratory birds

The Issue with Nighttime Lighting

The night sky is an amazing part of our environment shared by both people and wildlife. The cycle of day and night is essential for the natural rhythms of all living things, especially for the billions of birds that rely on it to navigate their nighttime migrations.

The use of artificial lighting at night, which is light created by people, has been increasing worldwide, and it alters the night sky. Most people can no longer step outside on a clear night and see a sky full of stars. While nighttime lighting often improves visibility and serves many purposes, it is important to use light in ways that minimize harm to humans, wildlife, and the environment. Unfortunately, nighttime lighting is often directed outward or upward, creating unnecessary and excessive light.

Why is this harmful to birds? Lighting can attract large numbers of night-migrating birds from as far as 5 kilometers away. This phenomenon is particularly prevalent on nights with low-cloud ceilings or foggy weather, when birds tend to migrate at lower altitudes where light reflecting on clouds disorient birds. Multiple mass-mortality events, each involving hundreds of birds, have been documented on such nights.

Throughout the year, nighttime lighting can affect birds by illuminating their habitats. This may cause birds to avoid habitats essential for their survival, altering local ecosystem dynamics. Birds that migrate or forage offshore are similarly disoriented by nighttime lighting from coastal areas and offshore vessels and structures

The good news: simple actions can help keep our night skies safe for birds year-round.

What Can We Do?

You can help solve this problem with the flip of a switch!

Turning off lights at night or minimizing unnecessary lighting helps restore natural darkness, creating a healthier environment for both people and birds.

Turn It Off

If the lighting is not needed, consider turning it off permanently or see “Timing” below.
Birds are at greater risk from lighting during spring and fall migration on cloudy nights. Consider if lighting can be temporarily turned off April-May and August-October, or at a minimum on cloudy nights during those months.
If birds become entrapped in an area of bright light that cannot be turned off permanently, turning lights off for 15 to 20 minutes can allow birds to escape the disorienting light and return to normal behavior. If you are unsure whether birds are or will be entrapped, plan regular breaks in the lighting or implement timers (see below) to allow an opportunity for birds to escape.
If you cannot turn off the lights completely at night, consider using bird-conscious lighting practices throughout the year. This is using lighting only where and when it is necessary and illuminating only the intended area. More specific recommendations follow.

a building with the lights on (left) and the lights off (right) — A nighttime view of a building in Portland, OR with the lights on (left) and then with the lights off (right). Portland Audubon's Lights Out Program is supported in part by the Service's Urban Bird Treaty Program. Courtesy of Ali Berman with Portland Audubon.

Timing

Limit lighting to necessary times only. Birds begin migrating overnight from dusk until dawn and are vulnerable to the negative effects of lighting throughout the night. Extinguish or dim unnecessary lighting, including in parking lots, after businesses or facilities close or around your home when you are in for the night, until dawn or when the facility opens, or lights are needed again in the morning.
Use networked lighting or automatic controls, such as timers, dimmers, or motion sensors, to turn lights on and off as needed.

Direction

Turn off lights that face up into the sky or lights that illuminate the surrounding landscape.
Avoid upward skyglow by selecting pre-certified fixtures or installing auxiliary shielding or positioning light fixtures where light is not emitted above the horizontal plane.
Keep lighting as low to the ground as possible, only illuminating necessary structures.

Prevent light spill from windows

Close blinds, shades, or curtains at night, and use automatic controls to turn interior lights on and off as needed.

Color and Brightness

Use amber, orange, red, or "warmer", light-emitting diodes (LEDs) or light fixtures with a color filter, which are less harmful for several species because they are less likely to trigger a behavioral response. Warmer colors have longer wavelengths (>560 nm) and lower correlated color temperatures (CCT < 2700 Kelvin).
Avoid using blue, white, or "cooler", LEDs or light fixtures, which are least favorable for birds, other wildlife, and people and contribute more to skyglow. Cooler colors have shorter wavelengths (<560 nm) and higher correlated color temperatures (>2700 Kelvin).
Keep the light as dim as possible, including adjusting to local conditions and ambient lighting. For example, natural areas should have little to no nighttime lighting unless necessary, compared to urban areas with high ambient lighting, where dimmed lights may not visibly contribute to skyglow.

The graphic shows four street lights in total. The light on the far left illustrates the problem with un necessary nighttime lighting, and the other three illustrate the possible solutions. (A full description can be found in the caption) — The graphic shows a series of streetlights that illustrate how nighttime lighting can unnecessarily illuminate areas beyond where it is useful, and different solutions. The first light on the far left shows a streetlight that is too bright and creates a large amount of light pollution. The second light is turned off with a clock-face icon below it to indicate that lights should be turned off when they are not needed, and this can be done with network or automatic controls like sensors or timers. The third light is less bright and has a shield added to it so that there is no uplight, and light is directed only to where it is useful. The fourth light is also much dimmer with a shield, and the light's color is amber, or “warmer”, with a correlated color temperature less than 2700 Kelvin, which reduces skyglow.

Benefits Of Bird-Conscious Lighting

Migrating birds are at risk of becoming disoriented and drawn into lighting, where they may collide with structures, unfortunately ending in tragedy. Giving special attention to lights during peak migration periods, in spring and fall, can help birds stay on track, increasing their chances of survival and successful breeding – which means more birds!

By applying these practices throughout the year, you can have an immediate impact on the environment around you. Not only will you be helping preserve the natural cycles that are so important to people, birds, and other wildlife, you will also save more money through less energy consumption!