Loons take about 3 years to sexually mature before they molt into the definitive breeding plumage and return to the north to nest.
Loons are actually more attached to their nesting lake than to a specific loon partner.
In the past many people and researchers believed that loons mated for life, but recent studies have shown that loons do switch partners from year to year. In fact, Dr. Walter Piper has been studying loons in the Rhinelander, Wisconsin area and has found that loons even switch mated within nesting seasons. For example, if the loon pair's first nest fails, the female loon may renest with another adult male bird the same season. A. Loons usually mate on the nest site. It is a quick process.