Painted Bunting is a much-beloved, polychromatic songster of the southern Great Plains, Texas, and the southeastern United States. It winters in west Mexico and south Florida, where is often brightens bird feeding stations.
There are two distinct populations of Painted Buntings, as can be seen on the above map. The bulk of the population involves the subspecies that is widespread in Texas, eastern New Mexico, Kansas, Oklahoma, Arkansas, and Louisiana, where it prefers mesquite shrublands, field edges, and scrubby second-growth. The eastern subspecies has a much smaller overall population that breeds on the Coastal Plain of northeastern Florida, Georgia, South Carolina, and southern North Carolina. These easterly birds are primarily responsible for the small wintering population in south Florida, the Bahamas, and Cuba, while westerly birds winter in west Mexico and Central America.
These two populations have quite different molt strategies with respect to migration, and these strategies correspond to general molt strategies for western birds versus eastern birds. Western Painted Buntings migrate early (beginning in July and August) and head to lush areas of west Mexico that become green with monsoonal rains. This provides a verdant and productive area for molting, so western Painted Buntings molt after migration. Eastern Painted Buntings already live in the humid southeast, so July and August are still verdant and productive in their breeding areas. These birds stay on the breeding grounds to molt, and migrate a bit later than the western birds, with peak migration from mid-September to mid-October.
The signal of these different molt strategies is faint on the STEM animation above, but it can be seen. Look for how coastal Georgia retains Painted Buntings in late October when all of the more westerly breeders have been long gone. The northward migration of both populations appears to occur at about the same time.