In the Western Hemisphere, many Arctic- and boreal-breeding species migrate to spend their nonbreeding season in southern South America, where they share environments with endemic and austral-migrant shorebird species. The habitats favored by shorebirds across their annual cycles — grasslands, wetlands, and beaches — have been altered dramatically over the last century. Shorebirds possess a unique set of life-history traits (e.g., small clutch size) that make them especially vulnerable to environmental and anthropogenic perturbations. The combination of threatened habitats, vulnerable life history, and wide-ranging migrations present significant conservation challenges for shorebirds.