Avian Surveys in the Korean Inner Border Area, Gimpo, Republic of Korea

Abstract

Birds are useful environmental indicators and their presence as their presence reflects the health of the food web. Bird occurrence, rarity and abundance are reliable indicators of the presence of ecosystem health. Monitoring of avian populations in the Republic of Korea (ROK) is a primary requirement due to plummeting populations and the risks to threatened species. Ministry of Environment, ROK started winter bird census from 1999 including inland areas and coast areas such as Cheorwon, Yeoncheon, Junam Reservoir and Han River. Cheolwon, Yeoncheon and some extent islands in the West Sea have been survey extensively due to iconic bird specise such as White-naped Crane (Grus vipio) or Red-Crowned Crane (Grus japonensis) wintering there. However, the winter bird census is not covered near Yu istet, Han River Estuary. Yu islet is located within the Han River estuary, a protected wetland in the Neutral Zone between the two Koreas and north of Gimpo in the ROK. The islet currently supports a large, mixed breeding colony of waterbirds such as one of the nation’s largest concentration of breeding Great Cormorants (Phalacrocorax carbo) and smaller numbers of breeding Black-faced Spoonbill (Platalea minor), Grey Heron (Ardea cinereal), Great Egret (Ardea alba) and Intermediate Egret (Ardea intermedia). The area has long been controled due to military reasons, but recently regular survey activity is possible supported by Gimpo city and military base in Gimpo from November 2018.Here, we provide data demonstrating that Yu islet is important for breeding for waterbirds; and that the northern Gimpo part of Han River estuary is also internationally important for waterbirds during migratory bird season as defined by the Ramsar Convention (Ramsar 1971, RRC-EA 2017). Especially, four waterbird species were found during the survey in the Main Survey Area: Swan Goose (Anser cygnoides), Taiga Bean Goose (Anser fabalis), Tundra Bean Goose (Anser serrirostris) and Greater White-fronted Goose (Anser frontalis). Once considered widespread in East Asia and abundant, the world population of Swan Goose is now estimated at only 60,000 - 78,000 individuals (Wetlands International 2020) and the species is assessed by BirdLife International as globally Vulnerable (BirdLife International 2020). The 1,010 Swan Goose counted on the vegetated mudflats at Jogang-Ri in the Main Survey Area on 27th November 2018 represents more than 1% of the total world population of this species. Notably, it is also the highest count of this species in the ROK for at least a decade. The count confirms the continuing international importance of the Han River estuary for the survival of the Swan Goose. The number counted in November had fallen to 250 by December 28th; and none were recorded in the Main Survey Area in January or February. Although searched for in March, none were noted during northward migration either. The surveys also found small numbers of nationally scarce Grey-capped Pygmy Woodpecker (Yungipicus canicapillus) in several areas of woodland surrounded by the Han River estuary. By selecting the most species-rich count within a given month in each of the two survey sectors, the number of species we recorded ranged from a minimum 29 in January to a maximum of 65 in April 2019. Based on the species recorded, the survey area is of clear importance for avian conservation. Its importance derives from the combination of the extensive areas of high-quality wetland and its geographic location within in one of the Korea Peninsula’s largest and most important remaining wetland ecosystems, the Han River Estuary. Our surveys resulted in the detection of a substantial number of bird species, especially in March and April when forest-breeding birds are more obviously vocal. The survey result is provided in the supplementary material (Suppl. material 1).

Keywords

• border area
• waterbirds
• bird conservation
• Neutra