Common loons breed on lakes and ponds in northern North America. They breed as far south as southern Minnesota and Wisconsin, and as far north as Greenland and Iceland.
Both male and female loons take part in the nest-building process, which occurs on the edges and shorelines of lakes and ponds. While loons can handle some disturbance, they seek out quiet locations with little human disturbance. Loons use a variety of objects to create their nests, including aquatic vegetation, grass and sticks.
Loons, especially young individuals, are susceptible to predation, especially from avian predators such as hawks, eagles and owls. As a result, they often build their nests in spots that provide them with overhead cover. Some examples include trees or bushes, bulrushes, and grass.
Loons are territorial birds and will defend their eggs and young against predators, including other loons. According to New England Nature, loon territory can range from 60 to 200 acres. As a result, small lakes and ponds may have only one pair of loons on them. There may be several nesting pairs of loons on larger bodies of water.