Light Pollution's Impact On Bird Migration Explained

Light pollution is a growing threat to wildlife, including many species of migratory birds. More than 80% of the world's population lives under a lit sky, with this figure rising to 99% in Europe and North America. Artificial light can interfere with the natural environment and is altering and adversely impacting wild species of animals. It can cause birds to change their migration patterns, foraging behaviours and vocal communication, resulting in disorientation and collisions.

Migrating birds are attracted to artificial light at night, especially during inclement weather events such as low cloud conditions, fog, rain, or when flying at lower altitudes. This lures them to dangers in cities, such as buildings and other man-made infrastructure.

Light pollution can also impact the timing of migration and other seasonal behaviours because it can disrupt biological clocks. For example, birds may misinterpret artificial light at night as a longer period of daylight, causing them to head off on migration earlier than usual. This mistiming could be an issue if the necessary environmental conditions and resources are not available for birds during migration or upon arrival at their destination.

Light pollution can cause birds to change their migration patterns, foraging behaviours and vocal communication

Light pollution can cause birds to change their migration patterns, foraging behaviours, and vocal communication.

Migration patterns

Migratory birds are attracted to artificial light at night, especially during inclement weather, when flying at lower altitudes, or when there are low clouds, fog, or rain. This attraction causes birds to alter their migration patterns and fly towards cities, where they circle illuminated areas, depleting their energy reserves and risking exhaustion. This disorientation also leads to collisions with buildings and other man-made structures, resulting in fatal consequences for the birds.

Foraging behaviours

Artificial light can also change birds' perceptions of habitat quality, leading them to select or avoid illuminated areas. For example, artificial light may attract birds to foraging grounds near cities or illuminated buildings.

Vocal communication

The exhaustion caused by circling illuminated areas and altered migration patterns can lead to an increase in vocal communication as birds call out in confusion. This, in turn, can attract more birds to the illuminated areas, resulting in more collisions and fatalities.

Artificial light at night can disrupt biological clocks, causing mistiming of migration

Artificial light at night can disrupt the biological clocks of birds, causing them to mistime their migration. This is because artificial lighting alters the natural patterns of light and dark in ecosystems, which can confuse birds and impact their behaviour.

Birds may misinterpret artificial light at night as a longer period of daylight, causing them to migrate earlier or later than they should. This mistiming can be an issue if the necessary environmental conditions and resources are not available during migration or upon arrival at their destination. For example, food may be scarce if birds arrive at their destination too early, and they may also face harsh weather conditions.

Additionally, artificial light can cause birds to deplete their energy reserves, putting them at risk of exhaustion, predation, and lethal collision with buildings and other man-made infrastructure. This is because birds attracted to lights may circle illuminated areas for extended periods, becoming exhausted, or fly towards lights and collide with windows or buildings.

Light pollution can cause bird collisions with buildings and other man-made infrastructure

Artificial light at night can disorient birds, luring them towards danger in cities. This can cause them to collide with buildings and other structures. Many birds migrate at night, and artificial light can attract them, acting like a "beacon". Bright lights on large buildings can attract birds in the same way that bright porch lights attract moths, resulting in fatal collisions.

Research has found that certain species are more susceptible to collision than others, and that vocalising while flying makes birds more likely to strike buildings. Seabirds are also adversely affected by artificial light at night, with petrels and shearwaters being the most affected.

While completely darkening cities is not a practical solution, researchers are investigating effective mitigation strategies that balance human needs for light with avian needs for darkness. Some cities have implemented "lights out" programs during bird migration seasons, and simple actions such as turning off unnecessary lights can make a big difference in reducing bird fatalities.

Light pollution can cause bird exhaustion, making them more vulnerable to predation

Light pollution can cause exhaustion in birds, making them more vulnerable to predation. Migrating birds are naturally attracted to artificial light at night, especially in low-visibility conditions like clouds, fog, rain, or when flying at lower altitudes. This attraction to artificial light can cause birds to become disoriented and circle illuminated areas, depleting their energy reserves.

The artificial light disrupts their natural migration patterns and behaviours, causing them to waste energy flying around and calling out in confusion. This confusion and exhaustion make them more susceptible to predators.

Additionally, the exhaustion caused by circling lights can leave them vulnerable to other urban threats, such as collisions with buildings and windows. This phenomenon has been observed in various bird species, including ducks, geese, sandpipers, songbirds, and seabirds.

The impact of light pollution on bird migration is a growing concern, and it is crucial to address this issue to protect migratory bird populations.

Light pollution can attract birds to cities, where they may become trapped and disoriented

Light pollution can be deadly for birds, contributing to the deaths of millions of birds each year. It can also cause birds to change their migration patterns, foraging behaviours, and vocal communication, resulting in disorientation and collisions.

Migrating birds are attracted to artificial light, especially during low cloud conditions, fog, rain, or when flying at lower altitudes. This lures them to cities, where they may become trapped and disoriented.

Birds are attracted to the steady-burning red and white lights of buildings and structures, and they can circle these illuminated areas for extended periods, leading to exhaustion and a depletion of their energy reserves. This makes them more vulnerable to predation and lethal collision with buildings and other man-made infrastructure.

Some bird species are more susceptible to collision than others, and certain species are identified as 'super colliders'. Migrating songbirds that vocalize at night during their flights are more likely to strike buildings than those that are silent. Additionally, birds vocalize more frequently when they are disoriented by artificial light, attracting additional members of their flocks and leading to more collisions.

Light pollution can also impact the timing of bird migration and other seasonal behaviours by disrupting their biological clocks. For example, birds exposed to artificial light at their overwintering sites may initiate migration earlier than other species. This mistiming can be detrimental if the necessary environmental conditions and resources are not available during migration or upon arrival at their destination.

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