On May 10th, World Migratory Bird Day was celebrated as billions of birds began their migration around that time. Representing “nearly one in five of the world’s 10,000 bird species”, announces Dr Ashton Berry, founder and director of BlueGreen Innovations, migrants are of critical importance.

Migrating for milder climates, abundant food, and more breeding space, these birds, in turn provide “a variety of ecosystem services, including pollination [and] seed dispersal”, explains Jon Carter, media manager at the British Trust for Ornithology (BTO). Some species that eat insects also help control pest populations, while others like ducks spread fish eggs, supporting aquatic biodiversity.

However, migratory birds are in danger. The 2024 UN report announced that nearly half of all migratory species are in decline.

One of the scourge declining migratory birds is urbanisation – the focus of this year’s World Migratory Bird Day – as “many of [them] visit or pass through urban environments” during their journey, says Dr Berry.

The problems

Loss and fragmentation of habitats in cities are among the “most pervasive threats to migratory species”, according to the UN Report. With urban environments expanding, natural lands are shrinking.

Cities, farms, and factories also fragment and isolate birds’ habitats, exposing them to new dangers they would otherwise avoid.

Moreover, urban areas often lack greenery like London, which had less than 1% of tree cover in 2018. Yet trees are crucial for migratory birds because they offer shelter during their long flights, provide food through fruits, flowers, seeds, and insects, and serve as nesting grounds.

Trees in urban environments are partially non-native species, which are less suitable for these animals and are often treated with pesticides, impacting insect populations in cities.

Migratory birds are also intensively burdened by collisions with windows and buildings. According to Dr. Berry, in Australia alone, in 2018, 2.7 birds per day died from a window collision.

But this is nothing compared to North America, which records more than one billion birds dying from glass and building strikes yearly, according to Carter, with migratory birds being the most impacted.

As Dr. Berry points out, “the number of birds striking windows is assumed to be much higher than reported as many bird strikes occur unnoticed”.

Although essential in fighting climate change and supporting our transition to clean energy, wind turbines are also an increasing threat, particularly wind farms located on migratory routes, as birds cannot avoid their large number and spinning blades.

In 2021, in the United States, 681,000 birds died due to wind turbine collisions. The American Bird Conservancy explains that with the increase in wind farms, 1.4 million birds could die from these impacts by 2030 if measures are not implemented.

Besides, mostly travelling at night, migratory birds are attracted to artificial lights from urban areas, which “may decrease the overall efficiency of migration by increasing time, energy requirements and increasing overall risk”, explains a 2017 study. “Artificial light can disorient and distract birds, adding to the collision risk”, adds Carter.

However, this problem also occurs during the day as the windows of buildings, bus shelters, or even houses reflect trees. By seeing the tree’s reflection, migratory birds approach windows and collide.

Dr. Berry insists, “The list of negative impacts goes on”, but everyone can help protect these feathered creatures.

Image credit: Brambling migrating during winters in Europe. Photo by Edmund Fellowes Provided to Greenauve by the British Trust for Ornithology (BTO).

The solutions

One simple solution is planting trees. In addition to helping ecosystems, plants have a real benefit on human wellbeing. BTO demonstrated that with more trees, “Residents of neighbourhoods with a high abundance of birds suffer less from depression and stress”.

However, plants must be carefully chosen. Dr Berry points out, “Native plant species provide a range of food resources, shelter, protection from predation, and places to build nests” that non-native species often lack. Check if your city has a guide for native plants.

Planting trees in the street can help reduce habitat fragmentation and provide safe passage for birds, while in parks, they can prevent competition among bird species. Gardens can also be a real oasis for migratory birds by providing “fruits, insects for food and vegetation for shelter”, notes Carter.

BlueGreen Innovations builds “a range of garden styles that mimic ecosystems,” explains Dr Berry, the brain behind this idea. “The focus is to build beautiful gardens that clients love, but also that benefit, through plant selections, the local biodiversity, [and] attracts birds, insects and butterflies”.

Furthermore, “contrary to what we once thought, providing food for birds in urban areas can be beneficial and make up for the losses in natural foods due to the impact of urbanisation”, says Dr Berry. The most important is the choice of food. Dr Berry advises “to check with your local bird experts”.

Collisions can also be mitigated to help migratory birds safely cross cities and buildings. Simple and cost-effective solutions, such as specific stickers, or installing nets in front of the windows can make them more visible. The US Fish and Wildlife Service provides a comprehensive list of solutions.

Image credit: Lesser kestrels, also known as Falco naumanni, mating in Herault, France. Photo by Pierre Dalous, licensed under CC BY-SA 3.0, via Wikimedia Commons.

For wind turbines, some advocate stopping them for a few hours when a flock of birds approaches. Similarly, France has recently decided to stop a wind farm for four months following the death of nearly 300 protected birds, the lesser kestrels. Other studies affirm that painting wind turbine blades in black could reduce bird strikes by almost 72%.

Finally, reducing the use of lights at night can significantly help birds during their flights. For example, “Some cities turn off lights at night during migration periods”, explains Carter.

Putting pressure on companies that use unnecessary artificial lights at night for marketing purposes, such as grocery shops, is another effective way to protect migratory birds.