Although nest prospecting, natal philopatry, and nest-site fidelity have been observed in many alcids, few data demonstrate these behaviors in Marbled Murrelets (Brachyramphus marmoratus). Prior to the 2003 breeding season, we installed a permanent video camera adjacent to a Marbled Murrelet nest site that had been used in 2001 and 2002. Video recordings in 2003 detected the simultaneous presence of 3 murrelets in alternate plumage on the nest branch, once during the incubation period, and once during the chick period. We did not observe aggression, suggesting familiarity between the extra-pair birds and site holders, and possibly avoidance of detection by predators. Without banded individuals we hypothesize extra-pair visitations at an active nest reflect nest-site prospecting, natal philopatry, or nest-site fidelity.