The skies over Britain are already changing shape. Cuckoos and swifts, among the earliest of the UK’s summer visitors to leave, have begun their journey south, with swallows and many warblers expected to follow in September, according to The Guardian’s Weatherwatch column. Arctic-breeding wading birds have started pausing at coastal marshes along the UK coastline to refuel before continuing further south.
But this year’s migration carries a heavier warning than usual. A major international review, led in part by the British Trust for Ornithology (BTO) and published in Nature Reviews Biodiversity in 2026, has found that more than half of the world’s migratory bird species are suffering significant population declines. The study, titled ‘Status, threats and conservation of Earth’s migratory birds’, documents losses across every major global flyway.
A flyway under pressure
Among the routes singled out is the African-Eurasian Flyway, the corridor stretching from the Arctic to southern Africa that carries many of the birds now leaving British gardens and hedgerows. It is used by more than 500 migratory species, according to BirdLife International, including the Swallow, Common Cuckoo, European Turtle Dove, Common Swift and Common Nightingale.
According to BirdLife International Africa, between 40% and 50% of migratory species using this flyway are in decline, out of an estimated 2 billion birds that travel it annually. At least 10% of species on the route face the threat of extinction, BirdLife says. A separate assessment by the UN Convention on Migratory Species found that 44% of the 1,189 migratory species it monitors worldwide are declining, with 22% threatened with extinction, pointing to overhunting, overfishing, habitat loss, warming and pollution as the main drivers.
Threats stack up across continents
The researchers behind the Nature Reviews Biodiversity study identified a tangle of interacting threats facing migratory birds at every stage of their annual journeys: habitat loss, climate change and extreme weather, invasive species, collisions with infrastructure such as buildings and power lines, disease, and pesticide use. Because these species cross so many borders and ecosystems in a single year, the authors argue that protecting isolated breeding or wintering sites is not enough.
Instead, they call for conservation strategies that address threats along entire migratory routes, an approach increasingly supported by advances in satellite tracking and acoustic monitoring that let scientists follow individual birds across thousands of kilometres.
“If any group of species remind us of the huge importance of working together to give our natural world a brighter future, it’s surely migrant birds,” said Juliet Vickery, Chief Executive of the British Trust for Ornithology.
Vickery added that the scale of the response needs to match the scale of the problem. “What we need now is action at a similar scale to ensure these species continue to cross continents and connect communities for generations to come,” she said, according to BirdGuides.
For now, the migration continues as it has for millennia, with cuckoos, swifts and waders following ancient routes south. Whether those routes remain viable for future generations of birds, researchers say, will depend on coordinated action across the many countries those journeys pass through.
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