Juvenile common loon (Gavia immer) taking off. Juvenile loons are on their own after about 12 weeks. The parents head off on migration in the fall, leaving juveniles to gather into flocks on northern lakes and make their own journey south a few weeks later. Once the juveniles reach coastal waters on the ocean, they stay there for the next two years. In the third year, young loons return north, although they may not breed for several more years (on average they are six years old when they start breeding). La Mauricie national park. Quebec. Canada