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Explained: Light Pollution and How it Affects Migratory Birds

This year’s World Migratory Bird Day throws light on the dark side of light pollution

Light Pollution

The theme of this year’s World Migratory Bird Day (WMBD), observed on May 14 this year, is “dim the lights for birds at night.”

Light pollution, due to artificially lit outdoor areas, has seen an increase of 2.2 per cent per year from 2012 to 2016, says a study cited by the Secretariat of the Convention on Migratory Species of Wild Animals (CMS), a UN environmental treaty.

Currently, more than 80 per cent of the world’s population is estimated to live under a “lit sky”, and the figure is closer to 99 per cent in Europe and North America. This has altered natural patterns, affecting many species, especially those migrating from one place to another.

“Natural darkness has a conservation value in the same way as clean water, air and soil. A key goal of World Migratory Bird Day 2022 is to raise awareness of the issue of light pollution and its negative impacts on migratory birds,” said Amy Fraenkel, the CMS Executive Secretary.

What is Light Pollution?

Artificial light alters natural patterns of light and dark within ecosystems, and contributes to the deaths of millions of birds each year.

Light pollution 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 when there are low cloud conditions, fog, rain, or when flying at lower altitudes, luring them to dangers in cities. Birds become disorientated and, as a result, may end up circling in illuminated areas. This leads to their energy reserves getting depleted, resulting in risks of exhaustion or worse.

“Many nocturnally migrating birds such as ducks, geese, plovers, sandpipers and songbirds are affected by light pollution causing disorientation and collisions with fatal consequences,” said Jacques Trouvilliez, Executive Secretary of the African-Eurasian Waterbird Agreement (AEWA), another UN treaty.

“Seabirds such as petrels and shearwaters are attracted by artificial lights on land and become prey for rats and cats,” added Trouvilliez.

How to Save Birds from Light Pollution?

More and more cities worldwide are taking measures to dim building lights during migration phases in spring and autumn, according to the UN Environment Programme (UNEP).

Two years ago, countries that are party to the CMS endorsed guidelines on light pollution covering marine turtles, seabirds and migratory shorebirds.

The recommendations call for environmental impact assessments to be conducted for projects that could result in light pollution. The projects should consider the main sources of light pollution at a certain site, the likely wild species to be affected, and facts about proximity to important habitats and migratory pathways, say experts.

Next year, new guidelines focused on migratory landbirds and bats will be presented for adoption at a CMS conference.

Importance of World Migratory Bird Day

The day is celebrated twice a year, on the second Saturday in May and October, in recognition of the cyclical nature of bird migration and the different peak migration periods in the northern and southern hemispheres.

It is organised by a collaborative partnership among the two UN wildlife treaties and the non-profit organisation, Environment for the Americas (EFTA). “The day is a call to action for international migratory bird conservation,” said EFTA Director Susan Bonfield.

As migratory birds’ journey across borders, inspiring and connecting people along the way, it is our aim to ensure safe, dark skies for their migration, Bonfield added.

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