Population trend and spatio-temporal distribution of Greater White-fronted (Anser albifrons) and Bean Geese (Anser fabalis) in Korea

Abstract

Geese have undergone significant changes in their distribution and population size due to human-induced impacts. To improve our understanding of the two main geese populations in East Asia — Greater White-fronted (Anser albifrons; GWFG) and Bean Geese (Anser fabalis sensu lato; BEAG), which includes the Tundra A. f. serrirostris (TDBG) and Taiga Bean Geese A. f. middendroffi (TGBG) — this study estimated their long- and short-term trends and the migration strategies based on their distribution during the migratory and wintering seasons, using nationwide census data collected over 24 years in Korea. The TRIM (TRends and Indices for Monitoring data) analysis supported a robust long-term population increase since 1999, recently stabilizing around 150,000 individuals in GWFG and 100,000 in TDBG, respectively. But TGBG stabilized at around 7000 with no significant change of population over time. The shorter-term trends within a season suggested that wintering populations of GWFG and TDBG in China might stop over in Korea in their autumn migration before their sea-crossing, evidenced by the large congregation near the Yellow Sea coast followed by gradual decrease. In contrast to autumn, there was no similar peak in spring migration, suggesting the potential for elliptical migration of some populations around the Yellow Sea. Our findings indicate a growing East Asian population and implies one of the migration strategies of the Greater White-fronted and Tundra Bean Geese. By collaborating with recent tracking data, long-term monitoring efforts could offer more detailed insights into population trends and migration strategies, thereby contributing to the effective management and conservation of goose species in East Asia.