<p>Half of all migratory bird species have declining population sizes. Losses span every region on Earth and raise urgent concerns for the long-term persistence of one of the planet’s most visible and ecologically important groups. Without intervention, continued declines and extinctions are inevitable. In this Review, we discuss current trends, threats and conservation responses for migratory birds. The true status of Earth’s migratory birds remains uncertain as monitoring is constrained by technical and financial limitations and geographic biases, particularly in the Global South. Identifying where declines occur and their causes remains challenging because migrants traverse vast ecological and political landscapes, complicating diagnosis and response. Current conservation momentum is focused on area-based and threat-based approaches, yet most migratory birds spend the majority of their life cycles outside protected areas, and threat mitigation remains largely localized, underscoring the need to advance species-level approaches that target limiting factors before populations become threatened. Reversing declines requires a coordinated framework that integrates full annual cycle understanding with human dimensions, expands monitoring, prioritizes landscape-scale habitat protection, delivers targeted threat reduction, and strengthens governance and financing, supported by precautionary action and more effective communication to conserve Earth’s migratory birds.</p>