We observed a male Razorbill (Alca torda) residing among a group of breeding Common Murres (Uria aalge) on Great Island, Newfoundland, during 1996–2000. Behavioral observations indicated that the presence of the Razorbill directly contributed to the break-up of one pair of murres and prevented another pair from producing an egg. In addition, murres with sites close to the Razorbill site may have experienced increased energetic demands arising from aggressive interactions frequently initiated by the Razorbill. A consequence of the presence of a heterospecific resident in a seabird colony may be decreased reproductive success for individuals breeding nearby.