Passage Summary: Even though there are plenty of empty lakes available, many loons prefer to pick a fight and try to kick another pair out of their home rather than just moving into a vacant spot.

Reasoning: Migratory loons frequently choose to fight for a territory already occupied by another pair, even when perfectly good vacant lakes are available nearby.

Analysis: The surprising behavior is the loons' preference for conflict over convenience. Why would a bird risk a fight for a house when the identical house next door is empty? To explain this, we need a reason why an occupied lake is actually more desirable than a vacant one. Perhaps the presence of a breeding pair serves as a 'quality seal' of approval, proving the lake is actually capable of supporting a family, whereas a vacant lake is an unproven risk.