Reproduction among close relatives is rare in birds. Here we report two cases of pair formation between mothers and sons in a marked population of Common Loons (Gavia immer) in northern Wisconsin, one of which resulted in the fledging of a chick. Short distance natal dispersal by males coupled with short distance breeding dispersal by adults after territorial displacement sets the stage for occasional mother-son pairings in this species, although data from multilocus DNA fingerprints indicate that such pairings are infrequent.