Most field guides separate this species into three distinct forms: the Pacific or Black Merlin, the Taiga Merlin, and the lightest form, the Prairie Merlin. Each of these races occupies a different breeding territory, and each pursues a different migratory strategy. Pacific Merlins are the least migratory, remaining in the vicinity of British Columbia and along the coast to Northern California. Taiga Merlins are the most migratory, moving south along both coasts and spending the winter in coastal areas where shorebirds are plentiful, especially Florida and the Caribbean. Taiga Merlins also occupy winter habitats in the desert Southwest and similar habitats as far south as northern South America. Prairie Merlins are only partially migratory in parts of their range, though most members spread out across the Southwest and northern Mexico.
To see the greatest number of migrating merlins, visit the hawkwatch site at Kiptopeke State Park in late September or the site at Curry Hammocks in the Florida Keys in early October.