Do Loons Mate Outside the Pair Bond?

No. Despite their quirks, loons are strictly faithful to their mate. That is, females stay very close to their mates during the period when their eggs are fertilized, and of the hundreds of copulations we have observed, not a single one has occurred outside of the pair bond. We know from DNA fingerprinting, moreover, that all chicks reared by a territorial pair are their true biological offspring.