By Peter Marra and Nathan W. Cooper

Every year, billions of migratory birds link continents, oceans, and ecosystems as they make long journeys between feeding areas and breeding grounds.

A bobolink (Dolichonyx oryzivorus) leaves the grasslands where it breeds in North America for the Pampas of South America. A Newell’s shearwater (Puffinus newelli) spends months gliding over the North Pacific before returning to the Hawaiian Islands to breed. A spoon-billed sandpiper (Calidris pygmaea) travels from Arctic Russia to the rapidly disappearing tidal mudflats of Southeast Asia for its nonbreeding season.

The three birds differ sharply in habitat, migration routes, and the threats they face. Yet they share a defining trait: Their survival depends on connected networks of habitats that extend across thousands of miles and multiple countries.

All three species, along with many other migratory birds, are now in difficulty. Their migrations remain among nature’s most remarkable spectacles, but the birds themselves face increasing risk as the habitats and ecological connections they rely on are lost or degraded, and as threats to survival and reproduction intensify.

As scientists who study migratory birds, we worked with an international group of colleagues on a comprehensive assessment of the status, threats, and conservation efforts involving more than 3,380 of Earth’s migratory bird species. The study was published at

The findings are sobering. More than half of the world’s migratory bird species are declining because of multiple threats, including habitat loss, invasive species that harm birds, collisions with buildings, hunting, the pet trade, toxic pesticides, and, in some cases, entanglement or capture in commercial fishing nets.

The study also points to a more hopeful conclusion. Scientific understanding of migratory birds has changed dramatically over the past two decades, and conservation can help protect these species if governments act before they become endangered.

Protecting Birds Across Their Full Journeys

Migratory bird conservation can better protect birds and their habitats if it focuses on their full annual cycles, from breeding grounds to nonbreeding areas and the migratory routes between them.

This approach combines the protection and restoration of important places with efforts to reduce threats wherever they occur. It also depends on international cooperation and proactive conservation led by engaged governments before species reach endangered status. Because many migratory birds cross several national borders during a single year, gaps in protection in one country can undermine conservation gains made elsewhere along the route.

Migratory birds are more than extraordinary travelers. They pollinate plants, disperse seeds, control agricultural pests, move nutrients between ecosystems, and support local economies by attracting birdwatchers and ecotourism. Their declines are not only a loss of biodiversity; they are also a signal of growing stress in ecosystems that support both wildlife and people.

There is encouraging news: Humans have never had better tools to help reverse these declines. Miniature tracking devices, genetics, automated radio telemetry networks such as Motus, long-term monitoring, and citizen-science initiatives such as eBird, which document bird numbers around the world, have transformed what scientists know about migratory birds’ behavior and the risks they face.

For the first time, researchers can track individual birds across continents and identify where conservation measures are most likely to have the greatest impact.

A New Conservation Strategy

For much of the past century, migratory bird conservation centered on protecting important places, including breeding areas, wetlands, nonbreeding habitats, and migration stopover sites.

That strategy has been highly successful and remains essential. Protected areas have prevented countless extinctions and will continue to be a cornerstone of biodiversity conservation.

However, research has shown that protecting places, while necessary, is often insufficient for species whose lives unfold across continents and oceans. Conservation efforts also need to identify where and when populations are most at risk, and address those constraints across birds’ entire annual cycles.

The three species described above show why this broader approach matters.

Bobolinks breed across North American grasslands but spend much of the year in South America. Protecting breeding habitat alone cannot reverse their declines if grasslands continue to disappear elsewhere, or if birds are poisoned by pesticides.

Newell’s shearwaters spend most of their lives over the Pacific Ocean but return to Hawaii to breed. There, artificial lights, collisions with power lines, and introduced predators such as domestic cats threaten populations that are already vulnerable.

Critically endangered spoon-billed sandpipers rely on a shrinking network of tidal mudflats that serve as stopover sites between breeding grounds on Russia’s Chukotka Peninsula and nonbreeding areas in Southeast Asia. The loss of even a few of these staging areas can endanger one of the world’s rarest migratory birds.

Each species needs a different conservation strategy. All, however, require the same underlying approach: conservation across the entire annual cycle rather than a focus on one place, season, or threat.

That approach is already beginning to take hold in the United States and shows what is possible.

What Success Can Look Like

Road to Recovery is an international initiative created to reverse declines among North America’s fastest-declining bird species before they require protection under US endangered species legislation.

Instead of waiting for populations to collapse, Road to Recovery brings together scientists, governments, conservation organizations, landowners, and local communities to form species working groups. These groups identify the harms bird populations face and help target limited conservation funding more precisely.

More than 50 international working groups are now developing conservation strategies for species ranging from bobolinks and lesser yellowlegs (Tringa flavipes) to evening grosbeaks (Coccothraustes vespertinus) and yellow-billed cuckoos (Coccyzus americanus). Their work has already contributed to new research, habitat protection, policy changes, hunting reforms, and international partnerships.

International agreements, including the Convention on the Conservation of Migratory Species of Wild Animals, as well as regional flyway partnerships and treaties, give nations mechanisms to cooperate on migratory species conservation across political borders.

However, the convention’s effectiveness is severely limited because many of the world’s largest, wealthiest, and most influential countries have not joined it. Those countries include the United States, Canada, Mexico, Russia, and Japan.

Broader international participation and sustained government investment could help turn scientific knowledge into coordinated conservation action across the full annual cycle.

Governments, however, cannot carry out this work alone. Landowners, businesses, conservation organizations, and individuals all have roles to play. They can help protect and restore habitat, reduce threats such as free-ranging cats and building collisions, support bird-friendly policies, and participate in citizen-science programs that help track migratory bird populations.

Applying the Lessons

There is strong reason for hope. Around the world, conservation initiatives have repeatedly shown that when threats are identified and addressed, bird populations can recover.

The pesticide DDT nearly caused the extinction of species such as the bald eagle, peregrine falcon, and osprey. People intervened, banned its use, and all of those species recovered.

The challenge now is to apply what science has shown.

Next spring, bobolinks will again return to North America’s grasslands. Newell’s shearwaters will navigate thousands of miles of open ocean back to Hawaii. Spoon-billed sandpipers will again attempt one of the world’s most extraordinary migrations.

Whether future generations will continue to witness these migrations depends on the choices current generations make and the steps they take to protect them.

THE CONVERSATION VIA REUTERS CONNECT

Peter Marra is the dean of The Earth Commons and professor of Biology and the Environment at Georgetown University. Nathan W. Cooper is a research ecologist at the Smithsonian Institution.