The article represents a survey of the avifauna of the Fildes Peninsula, concentrating on the dates and length of the reproductive cycle and based on field observations during the 26th Soviet Antarctic Expedition in 1981–1982. A total of 12 species was found to be nesting, while a further six species have been recorded as visitors. In many species the length of the reproductive cycle is identical with that for birds from the Haswell Archipelago in East Antarctica; however, the start of egglaying, and hence of all other activities may be later by up to two weeks in the case of the Fildes Peninsula populations. Snow cover on the nesting sites appears to be a critical factor here. The overall control on dates and length of the breeding season in both areas is food availability. In terms of adaptation of the reproductive cycle to environmental conditions, the birds of King George Island are thus intermediate between antarctic and subantarctic avifaunas.