They readily settle on stretches of still water ranging in size from small pools to large, deep lakes, and sometimes even nest on sheltered coasts. They are monogamous and pair for life. They are very territorial, but the area they defend is small. Pairs established from the previous season probably remain together throughout the winter, and start nesting early on after a minimal amount of display. Even newly formed pairs have simple courtship displays.
Copulation takes place on dry land and is repeated frequently.
It may begin on their day of arrival at the nest and continue until all eggs have been laid. The male selects the nest site. Since loons have difficulty in walking, the site is always close to water. The nest is simply a heap of plant matter. Breeding starts in May in the south of the range, and in the north, timing depends on when spring thaw occurs.