Outlook for migratory species worsens amid habitat loss & avian flu, report finds

A U.N.-backed report finds that nearly half of the world’s migratory species protected under a global treaty are now decreasing — and about one in four now faces extinction.
Habitat loss and degradation as well as hunting and fishing are driving these declines, but a deadly virus, Highly Pathogenic Avian Influenza, is also taking a heavy toll on bird populations.
Wildlife corridors and protected ocean networks can play a pivotal role in conserving imperiled species: Animals need to move to find food, a mate and migrate.

From shorebirds flying between their Arctic breeding grounds and southerly foraging ranges to freshwater fish returning to native spawning streams, migratory animals are struggling. About half of all migratory species populations protected under a global treaty are now in decline, with the situation worsening in just the last two years, according to a new United Nations-backed report.

When the first State of the World’s Migratory Species report was published in 2024, 44% of migratory species populations listed under the U.N. Convention on the Conservation of Migratory Species of Wild Animals (CMS) were declining, according to data from the IUCN Red List, the world’s most comprehensive guide to global extinction risk. Since then, the proportion of imperiled CMS-listed species rose to 49%, according to updated Red List data and new research.

Though the next status report isn’t due until around 2030, conservation advocates said the deteriorating situation required an interim report, as many countries are moving in the wrong direction when it comes to conserving wildlife that depend on various habitats to complete their life cycles.

“This [interim report] is saying there are some alarming trends in the meantime; that we don’t want to wait six years to talk about this,” said CMS executive secretary Amy Fraenkel.

Jaguars have no subspecies. Their range extends from Mexico to Argentina, but some populations are cut off, at risk of inbreeding and the demise that comes with it. Image by Gregoire Dubois.

The convention, established in 1979, aims to conserve migratory species by protecting their passageways across international borders, acknowledging that migratory species come with complex management challenges. Animals that cross borders may face vastly different conservation laws. A threat in any part of their migration route can affect their entire population — and also impact distant ecosystems where they fill an important ecological niche.

As of 2025, 132 countries and the European Union have signed or ratified the CMS agreement. Nearly 1,200 migratory species are listed, in need of protection by governments, including the blue whale (Balaenoptera musculus), green sea turtle (Chelonia mydas), Siberian crane (Grus leucogeranus) and saiga antelope (Saiga tatarica).

The new interim report, released ahead of the 15th CMS summit in Brazil later in March, finds that 26 CMS-listed migratory species have moved to a higher extinction risk category, including 18 shorebirds.

And it notes that recently published studies confirmed declining population trends for animals on land, in freshwater and in the ocean, including raptors in the African-Eurasian flyway, freshwater fish and both sharks and rays. Overall, one in four CMS-listed migratory species is now threatened with extinction.

Recently published studies show declining populations of animals on land, in freshwater and in the ocean. Hammerhead sharks, like the ones pictured here, as well as many other species of sharks and rays are among them. — Hammerhead sharks, like the ones pictured here, and many other species of sharks and rays are among imperiled migratory species. Image by Masayuki Agawa via Ocean Image Bank.

Drivers of decline

Animals depend on migration to breed, find food as the seasons change and to escape harsh weather. Blue wildebeest (Connochaetes taurinus), for example, migrate across the Serengeti-Masai Mara Ecosystem Corridor in Tanzania and Kenya to follow fresh grass after seasonal rains. Some humpback whales (Megaptera novaeangliae) travel thousands of miles from warm breeding waters in the tropics to cold Antarctic waters to hunt for krill.

Habitat loss has long jeopardized such ancient routes, trapping animals in place and decimating populations. With a burgeoning human population now nearing 8.3 billion, roads and development of all kinds have fractured wildlife corridors. Hunting, poaching and fishing, too, have taken a serious toll.

It’s growing increasingly difficult for elephants to move along their traditional migration routes. Image by Steve Winter.

However, the report notes that, for the most part, it’s unlikely these drivers are responsible for such substantial declines in just two years’ time.

“We’ve realized that even in the few short years between the last report and this report, there have been these important changes in declines in the population,” said the report’s lead author, Kelly Malsch, with the U.N. Environment Programme. “Some of it will be new data and new information that has come to light because Red List assessments aren’t done every year.”

Bird species, however, are assessed by the IUCN more regularly and comprehensively than almost any other group of animal, and that makes the real-time impacts clearer. Though the interim report doesn’t attribute why, exactly, species that were once stable are now in decline, it does highlight the devastating impacts of highly pathogenic avian influenza (HPAI) on birds around the world.

The Egyptian vulture can fly up to 640 kilometers (400 miles) in a day as it travels between its wintering grounds in the Sahara and European breeding sites — which is up to 5,000 km (3,100 mi). — The Egyptian vulture can fly up to 640 kilometers (400 miles) in a day as it travels between its wintering grounds in the Sahara and European breeding sites — a migration that of up to 5,000 km (3,100 mi). Image by Sergey Dereliev.

Avian influenza has been burning through global wildlife populations over the past five years, and migratory birds, in particular, have been hit hard. Waterfowl like ducks, geese and swans, as well as shorebirds, are the primary carriers and transmitters of HPAI. As birds fly from east to west, north to south — often congregating in the tens of thousands — they can rapidly spread the virus.

Avian flu have caused mass mortality events that threaten the long-term survival of migratory bird species across continents. Some 20,000 Peruvian pelicans (Pelecanus thagus) perished in Peru in 2023 out of a national population numbering less than 100,000. In East Asia, between 1,500 and 1,700 vulnerable hooded cranes (Grus monacha) died at their wintering grounds.

Other victims include the critically endangered African penguins (Spheniscus demersus), vulnerable Humboldt penguins (S. humboldti), near threatened Dalmatian pelicans (Pelecanus crispus) in Europe and Asia’s vulnerable red-crowned cranes (G. japonensis). Australia remains the only unaffected continent.

The most recent outbreak of this highly contagious virus began circulating among wild birds in Europe in 2020 and has since become the largest in history. This lethal strain, H5N1, is increasingly adept at leaping the species barrier: As of December 2025, H5N1 had infected 598 types of birds and 102 mammal species, pole to pole, according to an ongoing tally by the U.N. It has also infected people, with 71 cases in the U.S. and two deaths, though there have been no reports of human-to-human transmission.

But in birds and many other species, “Avian influenza is having a real impact, but it’s also compounded by wider threats such as habitat loss and degradation, overexploitation and climate change,” Malsch said.

Many bird species have lost vital stopovers along flyways, but with ongoing spread of Highly Pathogenic Avian Influenza, numbers have been decimated. Shorebirds have been particularly hard-hit, including pelicans. — Many bird species have lost vital stopovers along flyways, but with ongoing spread of Highly Pathogenic Avian Influenza, some populations have been decimated. Shorebirds have been particularly hard-hit, including pelicans. Image by Sergey Dereliev.

Safe passages

Roads, railways, fences and pipelines often block or imperil the seasonal, long-established migration routes of ungulates like deer and antelope. Such obstacles, the report finds, are worsening in places like Central Asia. The Mongolian gazelle (Procapra gutturosa), a nomadic species that travels some of the longest distances ever recorded, is losing range and has become significantly constrained over the past two decades.

In the Arctic, mining activities have been blamed, in part, for dramatic losses of tundra caribou (Rangifer tarandus). In 1986, 450,000 made up the Bathurst herd, north of Canada’s Great Slave Lake; by 2021, there were 6,240 left. Climate change has also taken a significant toll.

A critical step in conserving migratory species is mapping. It helps managers determine which habitats are most important, working up plans on how to protect or mitigate dangerous gaps in a travel corridors or networks, thereby ensuring access to conserved habitat where animals can safely feed, breed, and raise the next generation.

Improvements in animal tracking research over the past few decades have “drastically improved the state of knowledge in this area by enabling migration routes to be mapped in unprecedented detail,” the report states.

Researchers tracked a female whale shark 20,142 kilometers (more than 12,000 miles) on a migration, the longest recorded. Image by Noemi Merz via Ocean Image Bank.

“Corridors are a key part of the solution,” Fraenkel said. Creating areas that allow animals to pass safely across linear infrastructure — such as roads and railways — and navigate through fenced landscapes help animals on the move.

The protection of key areas within the Serengeti-Masai Mara Ecosystem Corridor, for example, has allowed one of the largest annual mammal migrations in the world to continue, ushering up to 2.5 million plains zebra (Equus quagga), Thomson’s gazelle (Eudorcas thomsonii) and wildebeest between grazing areas and water sources. During their yearlong trek, these African herbivores cover an area the size of Lesotho, 30,355 square kilometers (11,720 square miles).

The challenge with far-ranging migratory species, however, is that many animals move greater distances than can be easily conserved by just one national protected area or a small cluster of cross-border conserved spaces. Rather, protections need to target key habitats divided by tens of thousands of kilometers.

“One of the top priorities is to make sure there are interlinkages between different habitats across national boundaries,” Fraenkel said. But those parameters change a bit for ocean and avian animals. “When we talk about species in the ocean and birds, it’s more of a network of areas that are important. Not just adjacent contiguous land or sea.”

Though giraffes don’t migrate en masse like wildebeest, they, too, have seasonal movements to find food and water. Image by Mariola Grobelska via Unsplash.

The report does contain some bright spots. Since the reintroduction of scimitar-horned oryx (Oryx dammah) to Chad in 2016, the population has increased to 575 individuals. Saiga antelope populations, too, have rebounded after disease outbreaks threatened their survival in the 2010s.

At COP15 later this month, 42 new migratory species are being proposed for CMS listing, the largest-ever number, Fraenkel said.

“We know what needs to be done, and we look forward to galvanizing action by governments and other stakeholders to protect, conserve and save these species. There is no time to wait,” said Susan Lieberman, vice president of international policy at the Wildlife Conservation Society.

Munk's devil rays move in massive groups called “fevers” — often thousands of animals, migrating twice yearly to Baja California to feed and mate. — Munk’s devil rays move in massive groups called “fevers” — often thousands of animals, migrating twice yearly to Baja California to feed and mate. Image by Lars von Ritter Zahony via Ocean Image Bank.

Banner image: Sea turtles, another migratory species, need safe ocean passageways to move between feeding grounds and nesting beaches. Image by Jordan Robins via Ocean Image Bank.

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