October 8 marks the second of this year's World Migratory Birds Day, a campaign that aims to raise people's awareness over the conservation of migratory birds and their habitat. This year the theme is light pollution.

Light pollution poses serious threats to many aspects of life on earth, and migratory birds are one of the most affected. It is unknown why birds are so obsessive with city lights, but whatever the reason is, the excessive lights that are set up to beautify our cities cause disorientation to migrating birds.

According to a 2018 study using weather radar, even an individual light can trap the birds in endless circles which regularly cause them to die of exhaustion. Exposure to light at night also compromises the birds' immune systems, microbiomes, foraging behavior, and sleep cycles. This can kill millions of birds per year.

However, solutions are available, too.

More countries are dimming lights at night along migratory paths in spring and autumn. Scientists have been using weather radar that bounces off birds to track the intensity and moving locations of bird clusters, so that lights nearby can be turned off before their arrival. Best practice guidelines are also being developed under the Convention on Migratory Species to address this issue and ensure that action is taken globally to help birds migrate safely.

Since migrations take place at different times in different regions and countries, people may observe World Migratory Birds Day at various times, but the main days for the international celebrations always fall on the second Saturday in May and October.

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