Loons have been studied for years, but it has only been about 15 years that enough loons have been banded to really have a large enough population to understand the details of their behavior.
When loons are between 2-5 years old, they usually will select a vacant lake or territory to breed. As they get older they sometimes will try to evict a pair and claim their territory for their own. When an intruding female takes over a territory, the displaced female moves to an adjacent lake. However, it is a different story when the intruder is male. Apparently, about 30 percent of the territorial battles are fatal. If a loon is killed, it is almost always the resident male, never the intruder. It is the male loon that seems to select the nest site.
Watch the video below to see this unfold.