Every spring and fall, neotropical migrant birds fly thousands of miles between breeding areas in North America and wintering grounds in Central and South America, navigating by cues such as the sun and stars, visual landmarks, the earth’s magnetic field, and gravity. These migrants include many common species, such as warblers, vireos, hummingbirds, shorebirds, and some birds of prey, and they serve as indicators of environmental health. Populations of many of these birds have been declining because of habitat loss from forest destruction, wetland drainage, and urban growth in both North America and their wintering habitat in developing Latin American countries, as well as pollution, especially from pesticides, human disturbance, and predators including the common house cat. Their plight has recently gained attention, and programs focusing on these birds have begun.