The breeding success of Common Murres (Uria aalge) and Pelagic Cormorants (Phalocrocorax pelagicus) at Triangle Island, off British Columbia, Canada, was high from 2003 to 2006; four years in which a pair of Peregrine Falcons (Falco peregrinus) nested in the vicinity. However, in three years when the falcon eyrie was inactive (2007 to 2009), adult murres were depredated on the colony by Bald Eagles (Haliaeetus leucocephalus) and murre eggs were taken by Glaucous-winged Gulls (Larus glaucescens) after eagles flushed incubating murres. Consequently, breeding success in both species was low in 2007, then in 2008 and 2009 no murres bred successfully and no cormorants built nests. That a single pair of falcons protected thousands of seabirds is noteworthy for its local conservation implications. Bottom-up control of seabird breeding success has been well documented, but there appears need for a better understanding of the role of top-down mechanisms as a result of both the direct (consumptive) and indirect (non-consumptive) effects of top predators.