This entry in the Let's-Read-and-Find-Out series asks plenty of questions in a brief, lucid text, urging readers to think about what happens to birds in winter--how they return to their nesting grounds year after year across continents and oceans, and how they navigate by day, at night, and in fog. Gans (When Birds Change Their Feathers, 1980, etc.) answers some questions--making clear that there are still many mysteries in the field of ornithology--and discusses how scientists learn about migration through observation and experimentation. Appealing full-color illustrations complement and extend the discussion: close-ups of familiar neighborhood birds, some in unusually vivid plumage; dramatic views of flight; and accessible maps of migration patterns. A solid introduction to a fascinating topic and a welcome addition to the series.