During a 10-yr period, 28-45 pairs of Herring Gulls (Larus argentatus) have nested annually on the perimeter of the Ring-billed Gull (L. delawarensis) colony at Rogers City, Michigan. This represents about 4% of the total number of Herring Gull pairs present on the peninsula during this period. Herring Gulls choosing to nest close to Ring-bills do so in order to be near a preferred food source–Ring-bill eggs and young. The mean distance between perimeter Herring Gull nests and Ring-bill nests was 2.05 m. Aggressive encounters between the two species were regular but variable as some Herring Gulls appeared more tolerant of nearby Ring-bills. About half of the perimeter Herring Gulls preyed on Ring-bill eggs and young. About 78% of their capture attempts were successful. The mean number of chicks taken per observation hour was 0.19. Based on Ring-billed Gull reproductive rates for this colony and the observed predation rates for Herring Gulls, we calculated that about 10% of eggs and chicks lost annually are attributable to Herring Gull predation.