A virologic and serologic survey of arbovirus infections among seabirds and seabird ticks, Ixodes uriae, on Great Island, Witless Bay, Newfoundland, Canada, was conducted during 1971 and 1972. Kemerovo (Great Island, Bauline) and Sakhalin (Avalon) group viruses previously reported from birds and/or ticks on Great Island were prevalent among avian populations, while conclusive evidence of known nonindigenous serotypes was lacking. Circumstantial evidence—hemagglutination inhibiting antibody—of an unidentified member of the group B tick-borne encephalitis complex transmitted among marine birds of North America by I. uriae is reported. No evidence of human infections with any of these viruses was detected in a small number of biologists doing research on Great Island.