The study on the avifauna of the Seonheul Gotjawal region of Jeju-do (Is.), a survey site of long-term ecological study, was conducted between February of 2011 and January of 2012. A total of 54 species and 1,039 individuals of birds were observed, with 30 species and 164 individuals observed during spring, 31 species and 174 individuals during summer, 30 species and 206 individuals during fall and 28 species and 868 individuals during winter. In terms of dominant species, Mandarin Duck (Aix galericulata) was the most dominant at 500 individuals (48.12%), followed by Rook (Corvus frugilegus) at 250 individuals (24.06%), Black-billed Magpie (Pica pica) at 36 individuals (3.46%), Barn Swallow (Hirundo rustica) at 34 individuals (3.27%) and Great Tit (Parus major) and Japanese White-eye (Zosterops japonicus) at 26 individuals (2.50%) each. The overall species diversity was 1.95, with the value 2.69 during spring, 2.87 during summer, 2.81 during fall and 1.29 during winter. The species diversity was low during the winter, because Mandarin Duck (Aix galericulata) and Rook (Corvus frugilegus) were observed at a relative high level when compared to other species, at 500 individuals and 250 individuals respectively. Government protected species included 8 natural monument species, such as Mandarin Duck (Aix galericulata), Common Kestrel (Falco tinnunculus), Peregrine Falcon (Falco peregrinus), Cinereous Vulture (Aegypius monachus), Eurasian Sparrowhawk (Accipiter nisus), Northern Goshawk (Accipiter gentilis), Lesser Cuckoo (Cuculus poliocephalus) and Fairy Pitta (Pitta nympha), and 8 endangered species of Japanese Night Heron (Gorsachius goisagi), Peregrine Falcon (Falco peregrinus), Cinereous Vulture (Aegypius monachus), Crested Honey Buzzard (Pernis ptilorhychus), Northern Goshawk (Accipiter gentilis), Eurasian Sparrowhawk (Accipiter nisus), Fairy Pitta (Pitta nympha) and Black Paraside Flycatcher (Terpsiphone atrocaudata). Since subtropical birds, such as Japanese Night Heron (Gorsachius goisagi), White-bellied Green Pigeon (Treron sieboldii) and Chestnut-winged Cuckoo (Clamator coromandus) were observed during the study, there is a need for a continuous monitoring of their migratory pattern and breeding.