Migration Info Wilson's Warbler is represented in North America by three subspecies that probably have different migratory routes and schedules. The Pacific populations are the earliest migrants, arriving in British Columbia by the end of April. The other populations, which may cross any portion of the country from the Great Basin to the east coast, are relatively late migrants. The first arrivals are usually noted in the northern Great Lakes region in mid-May, but transients continue to pass through this area until mid-June. Recent studies indicate that the Pacific coast populations winter primarily in Baja California, Alaskan birds winter in the Honduras area, and the birds that winter in the central Mexican highlands come from several breeding sources. Wilson's Warblers are territorial in winter, and males and females are found in different habitats.