Seasonal Patterns of Bird Migration at a Stopover Site during the Migratory Period

This study focused on the seasonal pattern of migrant birds on an island that is used as a stopover site when they cross the Korean peninsula. Surveys were conducted on Oeyeon Island (N36°13′38″, E126°04′53″), which is located in the middle area of West Sea of Korea, during the spring (from March to May) and autumn (from September to November) migration seasons of 2011 and 2012. Increased number of individuals and species were observed on the Oeyeon Island during the spring season migration compared to the autumn season migration (mean±SD; species, spring 70.0±25.1 vs. autumn 49.0±9.1; individuals, spring 606.1±259.8 vs. autumn 280.9±77.2). Furthermore, this pattern was also observed for passerine birds (species, spring 47.6±17.4 vs. autumn 30.3±6.9; individuals, spring 518.7±263.6 vs. autumn 219.8±85.8). We suggest that physiological and ecological factors cause differences in the bird migration patterns between spring and autumn on the Korean islands, such as differences in the need for refueling after long-distance flight, selective pressure during the breeding season, and seasonal variation in the migration routes.