Do Loons Mate for Life?

No, loons do not mate for life. Far from it! Marking of individual adults with leg bands and study of marked breeding pairs has shown that loons commonly live for 20 years or more and often get evicted from territories. After eviction — which is common in both sexes — a loon moves to a non-territorial space nearby and begins to look for a new territory (and mate). A loon whose mate dies or is evicted behaves with similar pragmatism, readily establishing a new pair-bond with a replacement bird. Since they are long-lived and constantly threatened with eviction, most loons will have multiple mates during their lifetime. Still, loons are genetically monogamous; that is, the young reared together by a male and female are the true genetic offspring of both pair members — except for rare occasions when eviction occurs in the middle of a breeding attempt and the evicting loon accepts the biological offspring of his predecessor as his own.