Nearly half the world’s migratory bird species are in decline as the places they depend on along their epic journeys are disappearing or being degraded, putting growing pressure on birds that cross borders and continents to survive.
They are running out of places to rest, feed and breed as habitat loss, climate change, pollution, invasive species and human development disrupt the routes they have followed for generations.
These are the findings of a new edition of the State of the World’s Birds report, which warns that 45% of the world’s 1 843 migratory bird species are declining, while one in nine is threatened with extinction. The crisis is not confined to individual species or countries.
The sixth edition of the report, released by BirdLife International on Friday, focuses on migratory birds and the flyways they use for the first time.
According to the report, 30% of the world’s migratory bird species are stable, 14% are increasing while 11% have unknown trends. However, the report noted that many migratory species with stable or increasing global population trends are nevertheless experiencing declines in at least part of their range.
The report was launched at the Global Flyways Summit in Nairobi, alongside the Nairobi Flyways Declaration, an international commitment to coordinated action to protect migratory birds and their habitats across borders.
Flyways at risk
The decline of migratory bird species is particularly pronounced in certain flyways, the report said. Among the four terrestrial flyway systems, East Asia-Australasia has the highest proportion of declining species (53%), while 50% of all species that use the six marine flyways are in decline.
The East Asian–Australasian Flyway, used by more than 500 migratory species, has been particularly affected by coastal development and land reclamation in key wetlands, including the Yellow Sea. Across the flyway, the loss and degradation of inland and coastal wetlands is threatening migratory species and the ecosystem services these habitats provide.
The Far Eastern curlew, classified as endangered, has declined by 50% to 79% over the past three generations, largely because of habitat loss along the flyway.
Among the multitude of threats migratory species face, habitat loss is particularly damaging because migratory birds cannot simply compensate for the loss of one site by using another, the report said.
Migratory birds depend on an interconnected network of breeding grounds, stopover sites and non-breeding areas throughout their annual cycle to fuel their long-distance journeys.
When the habitats are lost or degraded, the network becomes fragmented, making it increasingly difficult for birds to complete their journeys.
Some groups are particularly affected: globally 54% of migratory shorebirds and 49% of migratory seabirds are declining. Species that use marine habitats, forests and coastal wetlands are also faring poorly, with 47% to 51% experiencing population declines.
Migratory shorebird populations are collapsing
The report assessed 1 099 Key Biodiversity Areas used by migratory species and found that 58% were in poor or very poor condition, indicating that populations of the bird species dependent on them had become depleted.
The consequences are particularly severe for shorebirds, which often depend on a relatively small number of highly productive sites where they can rest and refuel during migration. “Migratory shorebird populations are collapsing,” the report found.
In North America, 26 of 28 monitored shorebird species, or 93%, declined between 1980 and 2019, with more than half experiencing population declines of more than 50%.
More than half of migratory bird species use wetlands, while almost a third are highly dependent on them. Yet more than 3.4 million square kilometres of inland wetlands, an area roughly the size of India, have disappeared over the past 300 years.
The pressure continues to grow as climate change alters the conditions birds depend on along their routes. Globally, birds are advancing spring migration by an average of 2.1 days per decade, but the report warns that migration timing often continues to reflect historical rather than current environmental conditions.
By 2070, the average migration distance of 37 long-distance migratory birds in the African-Eurasian Flyway is projected to increase, with 37% of journeys requiring additional stopover sites.
Longer journeys could increase energy expenditure and mortality risk while increasing the potential for mismatches between migration and the availability of food.
Sea level rise poses another threat. In the East Asian–Australasian Flyway, up to 40% of intertidal wetland habitat used by 10 migratory shorebird species could be inundated during the 21st century.
Extinction of migratory bird species
Invasive alien species — organisms introduced by humans that establish outside their natural range — can affect migratory birds through predation, competition, disease and ecosystem disruption. Their impacts can occur at breeding grounds, stopover sites or elsewhere along the annual cycle.
One example is House mice on Marion Island, an important breeding site for migratory seabirds. Introduced in the 19th century, the mice began preying on seabird chicks after exhausting other food sources. Attacks are increasing and now affect adults as well as chicks.
If unchecked, mice are predicted to cause the local extinction of 18 of the 28 migratory seabird species breeding on the island, with some, including the Grey Petrel, potentially disappearing within 30 years, the report said.
Invasive species can also alter habitats and food webs. Common carp, found in more than 20% of the world’s river basins, degrade wetlands by disturbing sediment, increasing turbidity, reducing invertebrates and uprooting aquatic plants.
Highly Pathogenic Avian Influenza, or bird flu, has emerged as another major global threat. The H5N1 strain has spread along migration routes and infected almost 600 wild bird species across every continent, including Antarctica and, most recently, Australasia.
The scale of the threats facing migratory bird species is reflected in the report’s extinction figures. At least three migratory bird species have gone extinct since 1500, while another four are suspected to have become extinct.
In 2025, the extinction of the Slender-billed curlew was confirmed. It is described in the report as the first known global extinction of a bird from mainland Eurasia and Africa in recent centuries. Six other migratory species are confirmed or suspected to have been lost in the last 150 years.
The species was formerly widespread along the African-Eurasian Flyway, but drainage of breeding habitat for agriculture, the loss of coastal wetlands and hunting are suspected to have contributed to its disappearance.
Migratory bird species are sentinels
The response is increasingly being coordinated across flyways. The Asian Development Bank is mobilising $3 billion (R49bn) over the next decade to protect at least 50 priority wetlands in the East Asian–Australasian Flyway, while the Development Bank of Latin America and the Caribbean plans to mobilise $3bn to $5bn through 2050 to safeguard more than 30 landscapes and seascapes.
Migration itself can also be deadly. For three long-distance migratory raptor species in the African-Eurasian Flyway, mortality rates are around six times higher during migration than when the birds are stationary. More than half of their annual mortality occurs during migration.
Energy infrastructure is a major contributor. It accounts for 49% of human-induced mortality in large soaring birds in the African-Eurasian Flyway, with electrocution alone responsible for 41% of deaths.
Wind farms also pose risks. At least 362 bird species have been recorded as turbine-collision victims, with migratory species experiencing higher collision rates than non-migratory species.
But the threats do not end when birds reach the sea. Bycatch is described as the greatest at-sea threat to seabirds, with more than one million estimated to die every year after becoming hooked on longlines, struck by trawl cables or entangled in gillnets and purse-seines.
Every year, an estimated 160 000 to 320 000 seabirds are killed by longline fisheries, about 400 000 by gillnets and at least 44 000 by trawl fisheries.
Pollution adds another layer of pressure. Up to 23 million tonnes of plastic enter aquatic ecosystems each year, while artificial lighting has increased global night-sky brightness by about 10%.
Hunting and trapping remain widespread across migratory flyways. More than 60% of migratory bird species are used by humans in some way, including 62% of globally threatened species.
In the African-Eurasian Flyway, between 13.1 million and 42.7 million migratory birds are estimated to be illegally killed or taken every year across Europe, the Mediterranean, the Caucasus and the Arabian Peninsula.
Despite the scale of the declines, the report argues that the trajectory can be changed. It calls for conservation to be coordinated across entire flyways rather than focused only on individual countries or sites.
This means protecting and restoring critical habitats, maintaining connectivity between sites, reducing illegal killing and fisheries bycatch, tackling invasive species and making agriculture and forestry more sustainable.
It also calls for the impacts of energy infrastructure to be reduced and for climate adaptation to be incorporated into conservation planning.
“Migratory birds are sentinels and their declines reveal growing pressure on the natural systems that sustain us,” said Dr Stuart Butchart FRS, chief scientist at BirdLife International and senior editor of State of the World’s Birds.
“But the science is equally clear: conservation works, with co-ordinated action preventing extinctions and helping populations recover. The solutions exist: what is needed now is their implementation at flyway scale.”