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Common Tern reproductive success on Stratton Island, Maine, was severely affected in 1989 by nocturnal Black-crowned Night-Heron distriburance. Night-herons preyed upon tern chicks and caused adult nocturnal abandonment. Common Tern fledging success in 1989 was 0.24 (+/- 0.65) chicks/pair. Hatching success was significantly greater but fledging success was lower between early and late nesting terns. Night-heron disturbance allowed Herring and Great Black-backed Gulls, Ruddy Turnstones and ants access to the deserted nests. Nocturnal predators destroyed 51 nests in 1989, and 62 other nests failed due to adult abandonment of eggs and chicks. Our observations suggest that Common Terns cannot distinguish between the similar silhouettes of Black-crowned Night-herons and large owls after dusk and that night-herons alone may cause large-scale desertion in a tern colony.