Every year, billions of migratory birds connect the world’s continents, oceans and ecosystems as they undertake epic journeys between their foraging habitats and their breeding grounds.

A bobolink (Dolichonyx oryzivorus) leaves its breeding grasslands of North America for the Pampas of South America. A Newell’s shearwater (Puffinus newelli) spends months soaring across 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.

These birds could hardly be more different. They occupy different habitats, follow different migratory routes and face different threats. Yet they share one remarkable characteristic: Their survival depends on networks of habitats stretching across thousands of miles and multiple countries.

Today, all three species and many others are in trouble. Their migrations remain among nature’s greatest spectacles, but the birds themselves are increasingly at risk as the habitats and ecological connections they depend upon are lost or degraded and threats to their survival and ability to reproduce increase.

We study migratory birds as scientists. With an international group of colleagues, we just published a comprehensive assessment of the status, threats and conservation efforts involving more than 3,380 of Earth’s migratory bird species.

The results are sobering. We found that more than half of the world’s migratory bird species are declining because of an array of threats, including habitat loss, invasive species that harm birds, collisions with buildings, hunting, the pet trade, toxic pesticides and, in some cases, being caught in commercial fishing nets.

But our study offers a second conclusion with more hope. The science around migratory birds has changed dramatically over the past two decades, and conservation can help save these incredible species – if governments act before they become endangered.

Protecting birds across their epic........

© The Conversation