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. It is very rare to have three eggs or chicks. In Wisconsin the average production of chicks is about .7 chicks per pair.
Loons usually mate on the nest site.
It is a quick process. The male loon will approach the nest site and give a quiet call. If the female is interested, she will approach and climb onto the nest. The the male will climb on top of her and copulation occurs. It only takes a few moments and then he drops into the water.