Over half of world's migratory bird species are declining, global study finds

The declines signal a broader breakdown in ecosystems that sustain both wildlife and people, researchers warn

An ibis bird perches next to the Reserve Bank of Australia headquarters in central Sydney, Australia, Feb 6, 2018. REUTERS/Daniel Munoz

Every year, billions of migratory birds travel between continents, connecting ecosystems worldwide as they move between breeding grounds and foraging habitats.

A new global assessment finds more than half of these species are now in decline.

The study, by an international team of scientists, examined more than 3,380 migratory bird species.

Researchers found threats including habitat loss, invasive species, building collisions, hunting, the pet trade, pesticides and entanglement in fishing nets.

Despite the findings, researchers say conservation can still reverse these declines if governments act before more species become endangered.

The bobolink breeds in North America's grasslands before migrating to South America.

The Newell's shearwater returns to Hawaii to breed after months over the Pacific, facing threats from artificial lights and introduced predators.

The spoon-billed sandpiper, among the world's rarest migratory birds, depends on shrinking tidal mudflats in Southeast Asia as a stopover between Arctic Russia and its nonbreeding grounds.

All three of these species illustrate the issue at hand.

Protecting breeding grounds alone is not enough, the study finds.

Researchers say conservation must account for birds' entire annual cycle, addressing threats along their full migratory routes.

Migratory birds also pollinate plants, disperse seeds, control pests and support local economies through birdwatching, the researchers note.

Advances in tracking technology, genetics and citizen-science platforms like eBird have expanded understanding of migratory birds, helping researchers target conservation efforts more precisely.

One example is Road to Recovery, a US initiative aimed at reversing declines in the fastest-declining bird species before they need legal protection.

More than 50 working groups, bringing together scientists, governments and communities, are already active under the programme.

International treaties such as the Convention on the Conservation of Migratory Species of Wild Animals offer frameworks for cooperation, but researchers note major countries -- including the US, Canada, Mexico, Russia and Japan -- have not signed on, limiting its reach.

The study's authors call for broader international participation and sustained investment to protect migratory birds across their full annual cycle.