Figure 5. Inter-regional migration of IAVs driven by each species.

Squares with colors represent different continents, respectively. Regions belonging to the same continent were depicted with the same color. A possible migration event for the same species is indicated by a pair of squares placed vertically in the same year. Multiple inter-regional migrations in the same species for the same year are piled up vertically. Migrations that have been partially contributed by migratory birds are indicated by a horizontal line crossing the two regions.