A new study led by researchers from Georgetown University and a collaboration of ornithologists from many global organisations, including the State of India’s Birds (SoIB) partnership, has revealed that more than half of the world’s migratory bird species are declining.

The authors of the study published in Nature Reviews Biodiversity estimate that approximately 51% of migratory bird species are declining globally across every major flyway on Earth.

Biodiversity crisis

While nearly 300 migratory species are already considered globally threatened, many once-common and widespread birds are also experiencing substantial population losses, underscoring the scale of the biodiversity crisis.

In India, this paper found that long-distance migratory birds like those that visit India from the Arctic were declining more rapidly than resident birds or shorter-distance migrants.

“The scale of the migratory bird decline is both alarming and sobering. What we’re seeing is the predictable consequence of decades of environmental degradation. Yet these declines are not inevitable. This review goes beyond documenting the crisis by identifying the major threats, highlighting the critical knowledge gaps, and providing a science-based framework for reversing declines before more species are pushed toward extinction,” said Peter P. Marra, Dean of Georgetown University’s Earth Commons Institute and co-lead author of the study.

Most visible

According to the SoIB Partnership, migratory birds are among the most visible and widespread components of global biodiversity. It said that they help regulate insect populations, disperse seeds and pollinate plants, and support food webs across ecosystems and continents.

They are also one of the primary ways people connect with nature, with millions of birdwatchers and community scientists around the world contributing observations to global databases that have become essential for understanding bird populations and informing conservation action.

“Yet understanding exactly where and why populations are declining, and which of the world’s 11,000 bird species should be considered migratory, remains a challenge,” it said.

Use of technology

It added that scientists are increasingly using advances in tracking technology, community science initiatives such as eBird, AI-enabled acoustic monitoring, and population modelling to identify migration routes, understand how populations are connected across seasons, and uncover the drivers of decline, including habitat loss, climate change, invasive species, collisions with buildings and infrastructure, disease, and pesticide use.

The authors of the study further argued that reversing declines would require conservation strategies that address these threats across entire migratory lifecycles and international flyways rather than in isolation.

“Previous analyses have brought global attention to the fact that North American and European migratory birds are declining at alarming rates. But until now, we did not have a good assessment of how birds are doing across all of the global terrestrial and marine flyways,” said Nathan W. Cooper of Smithsonian’s National Zoo and Conservation Biology Institute and co-lead author of the study.