Much is still unknown about loon migration. Through the use of telemetry and color bands we have found that most of the loons in the midwest stage on the great lakes, mainly Lake Michigan, and then migrate down to the Gulf of Mexico. However, there is a small population that goes off the coast of the Carolinas too. The adults migrate first, usually 2-3 months after their chicks hatch so that their offspring are capable of surviving on their own, although adults will start their migration earlier if they fail to raise young. The chicks don't leave until nearly ice over. Exactly how they know where to go is still a mystery. While loons do not migrate in flocks, they usually congregate in large groups on staging lakes for their migration in order to hunt in a group, which increases their chances for getting a meal.
Once on the ocean, loons are able to adapt to living in salt water by using a salt gland that extracts the salt from the water and excretes it from ducts in the loon's beak. Loons also group together on the ocean in order to hunt better.
Loons start heading back to their breeding lakes as early as March, but won't actuallyarrive on their breeding lake until ice out, prefering to stay on staging lakes farther south until that time.
To see data on the first sightings of loons across the country, please visit http://www.learner.org/jnorth/maps/Sightings_All.html.
To see satellite tracking of loons, please visit http://www.umesc.usgs.gov/terrestrial/migratory_birds/loons/migrations.html.