Abstract
BackgroundThe vulnerable Chinese Egret (Egretta eulophotes) is a long-distance migratory waterbird whose migration and wintering information is poorly understood. This study aims to identify the autumn migration routes and wintering areas of juvenile Chinese Egrets and determine the migration movement traits of this species.MethodsThirty-nine juvenile Chinese Egrets from the Fantuozi Island, an uninhabited offshore island with a large breeding colony of Chinese Egrets in Dalian, China, were tracked using GPS/GSM transmitters. Some feathers from each tracked juvenile were collected for molecular identification of sex in the laboratory. The GPS locations, recorded at 2-h intervals from August 2018 to May 2020, were used for the analyses.ResultsOf the 39 tracked juveniles, 30 individuals began their migration between September and November, and 13 successfully completed their autumn migration between October and November. The juveniles migrated southward via three migration routes, coastal, oceanic and inland, mainly during the night. The migration duration, migration distance, flight speed, and stopover duration of the 13 juvenile egrets that completed migration averaged 5.08 ± 1.04 days, 3928.18 ± 414.27 km, 57.27 ± 5.73 km/h, and 23.08 ± 19.28 h, respectively. These juveniles wintered in the coastal wetlands of Southeast Asia including those in the Philippines, Vietnam, and Malaysia, and only one successfully began its spring migration in June 2020.ConclusionsThis study newly finds that the oceanic route taken by juvenile Chinese Egrets, suggesting that the juveniles are able to fly over the Pacific Ocean without a stopover. Moreover, our novel data indicate that coastal wetlands along the East Asian–Australasian Flyway are important areas for both autumn migration stopover and the wintering of these juveniles, suggesting that international cooperation is important to conserve the vulnerable Chinese Egret and the wetland habitats on which it depends.
Highlights
The vulnerable Chinese Egret (Egretta eulophotes) is a long-distance migratory waterbird whose migration and wintering information is poorly understood
Migration routes The juvenile Chinese Egrets departed southward from the vicinity of their natal island and underwent directional movements that continued to occur in a narrow range, with longitude ranging between 128.39° E and 105.76° E and latitude ranging from 40.55° N to 4.71° N
Global Positioning System (GPS) tracking data showed that the juvenile Chinese Egrets migrated via three routes: coastal, inland, and oceanic (Fig. 1)
Summary
The vulnerable Chinese Egret (Egretta eulophotes) is a long-distance migratory waterbird whose migration and wintering information is poorly understood. Seasonal climatic changes and food availability fluctuations drive many species of animals to migrate between breeding and wintering areas (Alerstam et al 2003; Newton 2008; Rappole 2013) For inexperienced juveniles, their long-distance migration is incredibly challenging (Klaassen et al 2014; Oppel et al 2015; Rotics et al 2016; Vega et al 2016) regardless of whether they travel by themselves (McKinnon et al 2014) or follow adults (Sergio et al 2014; Hewson et al 2016; Meyburg et al 2017). The Chinese Egret (Egretta eulophotes) (Pelecaniformes: Ardeidae) is a globally vulnerable species with an estimated population below 10,000 worldwide (BirdLife International 2020) It is a wetland-dependent bird, usually foraging in coastal wetlands, mainly breeding on offshore islands in eastern China, North Korea, South Korea and eastern Russia, and wintering in coastal regions of southeast Asia, with sightings of banded bird occurring in the Philippines, Indonesia, Malaysia, Singapore, Brunei, Vietnam and Thailand. Many studies have focused on the breeding behavior, feeding ecology and genetics of the Chinese Egret (Zhou et al 2010; Huang et al 2013; Wang et al 2013; Dai et al 2015; Lei et al 2016), and juvenile Chinese Egret migration data were collected from within China from 5 transmitters (Zhang et al 2018), the transnational migration and wintering areas of this vulnerable species have not been studied
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