This website distinguishes between “flyways” and “biogeographic realms”. The demarcation of biogeographic realms (which are divisions of the land masses of the world according to their distinctive floras and faunas) follows WWF (Figure 1) with the additional distinction between the east and west Palearctic realms. The term flyway is used in various contexts. Boere & Stroud defined the broad concept of flyways as: “…the biological systems of migration paths that directly link sites and ecosystems in different countries and continents”. More specifically, they define a flyway as “the entire range of a migratory bird species (or groups of related species or distinct populations of a single species) through which it moves on an annual basis from the breeding grounds to non-breeding areas, including intermediate resting and feeding places as well as the area within which the birds migrate.” This website follows the definition of the nine major waterbird flyways (Figure 2), based on the definition of flyways for shorebirds (some of the longest distance migrants) developed by the International Wader Study Group with the addition of the Central Pacific Flyway that is important for a limited number of migratory populations of waterbirds. A population is assigned to a flyway if the majority of the population performs regular latitudinal migrations stretching through two or more biogeographic realms, a classification which works well for a majority of waterbirds that migrate in the Americas, Asia-Pacific and Africa-Eurasia regions.