Avifauna of Gungdae Oreum and its seasonal changes in the Jeju Eastern Oreum Group in Jeju Island, Korea

Abstract ‘Oreum’ is a local common name for a volcanic cone in Jeju Island, Republic of Korea. Oreums in the Jeju Eastern Oreum Group (JEOG), located in the eastern mid-mountain region of Jeju, have been threatened by increasing tourism and associated development pressures; however, year-round monitoring activities on their ecological values have rarely been implemented. This study aimed to provide for the first time weekly monitoring information on the avifauna and its seasonal changes at Gungdae Oreum, covered by planted forest stands and located at the eastern end of JEOG, in order to bridge our knowledge gap on local ecosystems of JEOG. We surveyed weekly the avifauna for 51 weeks from July 2017 to July 2018 and documented a total of 4,763 birds from 69 species, including nine nationally protected species and 22 breeding species. Species richness and diversity indices calculated in each survey effort were not significantly changed by seasons, probably because the majority of the avifauna in JEOG were dominated by common resident forest birds. However, seasonal rarefaction curves revealed that more frequent and repeated surveys may document more species especially in spring and autumn migration seasons, suggesting that diverse migratory birds would pass through JEOG. The computed asymptotic richness was 83 species (95% confidence interval: 73-116) which is higher than the observed species richness (69 species) recorded over a year. This result also emphasizes the importance of long-term and multi-year monitoring programs with constant and standardized sampling efforts to better understand the local avifauna and biodiversity in forested environments.