Artificial Light Attracts Birds to Cities and Increases Mortality, Study

Every year, millions of birds migrate across continents and oceans, following the cues of nature to find food, breeding grounds, and suitable habitats.

But a new study published in the journal Nature reveals that artificial light at night (ALAN) is luring many of these birds to cities and sometimes to their deaths.

The study estimated that between 365 and 988 million birds die annually in the United States due to collisions with buildings, and that the majority of these fatalities occur at night.

It also identified the regions and species that are most vulnerable to collisions, and suggests conservation measures to reduce the impact of ALAN on birds.

The Deadly Attraction of City Lights

(Photo : NHAC NGUYEN/AFP via Getty Images)

Every year, millions of birds migrate across continents and oceans, following the cues of nature to find food, breeding grounds, and suitable habitats. But in their journeys, they encounter a new and unnatural obstacle: artificial light at night (ALAN).

ALAN is the result of human activities that illuminate the outdoor environment with various sources of light, such as street lamps, billboards, skyscrapers, and spotlights.

These night lights can interfere with the natural rhythms of birds and other wildlife, disrupting their biological clocks, navigation, communication, and behavior.

One of the most serious impacts of ALAN on birds is that it can attract and disorient them, especially when they fly at night or in low-visibility conditions.

Birds that use the stars, the moon, or the horizon to orient themselves can be confused by the bright and contrasting lights of cities, which can appear like celestial bodies or landmarks.

As a result, birds may deviate from their normal flight paths, lose their sense of direction, and end up circling or colliding with illuminated structures, such as buildings, towers, and power lines.

A recent study published in the journal Nature estimated that between 365 and 988 million birds die annually in the United States due to collisions with buildings, and that the majority of these fatalities occur at night.

The study also found that the mortality rate was higher for migratory birds than for resident birds, and that the risk of collision increased with the level of light pollution in the area.

The study used data from the US Geological Survey's North American Breeding Bird Survey and the Audubon Christmas Bird Count, as well as satellite imagery of night-time lights, to model the relationship between bird abundance, building density, and light pollution across the continental US.

The researchers identified the regions and species that were most vulnerable to collisions, and suggested conservation measures to reduce the impact of ALAN on birds.

Also Read: Humans to Blame for Pacific Bird Extinction, Representing 10 Percent of World's Bird Species

What Can Be Done to Save the Birds?

The study is not the first to highlight the threat of ALAN to birds. In fact, the issue has been recognized for decades, and several initiatives have been launched to raise awareness and take action.

For example, World Migratory Bird Day, celebrated on 8 October every year, has chosen the theme of "Sing, Fly, Soar - Like a Bird!" for 2022, and aims to illuminate the dark side of light pollution and its effects on bird migration.

There are also practical solutions that can be implemented to reduce the impact of ALAN on birds, such as:

•  Turning off or dimming unnecessary lights during peak migration periods, especially from dusk to dawn, and avoiding upward-facing or flashing lights.
•  Using motion sensors, timers, or shields to control the amount and direction of light, and choosing warm-colored or low-intensity bulbs that are less attractive to birds.
•  Designing bird-friendly buildings that minimize the use of glass, or applying patterns, films, or decals to make glass more visible to birds.
•  Creating or restoring natural habitats for birds in urban areas, such as parks, gardens, green roofs, and wetlands, and providing food, water, and shelter for them.
•  Supporting research, education, and advocacy efforts to raise awareness and promote best practices for reducing light pollution and protecting birds.

By taking these simple steps, we can help save millions of birds from the deadly attraction of city lights, and ensure that they can continue their amazing journeys across the sky.

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