Seasonal and regional differences in migration patterns and conservation status of Swan Geese (Anser cygnoides) in the East Asian Flyway

Abstract

Background The Swan Goose (Anser cygnoides) breeds across Mongolia and adjacent China and Russia and winters exclusively in China. It is globally threatened, showing long-term major range contractions and declining abundance, linked to habitat loss and degradation. We remain ignorant about the biogeographical subpopulation structure of the species and potential differences in their migration timing, stopovers and schedules, information that could be vital to effective conservation of different elements of the species population, which we address here with results from a telemetry study. Methods In 2017–2018, we attached GPS/GSM telemetry devices to 238 Swan Geese on moulting sites in three discrete parts of their summering area (Dauria International Protected Area, Central Mongolia and Western Mongolia), generating 104 complete spring and autumn migration episodes to compare migration speed and nature between birds of different summer provenances. Results Birds from all three breeding areas used almost completely separate migration routes to winter sympatrically in the Yangtze River floodplain. Although many features of the spring and autumn migrations of the three groups were similar, despite the significantly longer migration routes taken by Western Mongolian tagged birds, birds from Dauria Region arrived significantly later in winter due to prolonged staging in coastal areas and took longer to reach their breeding areas in spring. Among birds of all breeding provenances, spring migration was approximately twice as fast as autumn migration. Areas used by staging Swan Geese (mainly wetlands) in autumn and spring almost never fell within national level protected areas, suggesting major site safeguard is necessary to protect these critical areas. Conclusions This study showed the discreteness of migration routes taken by birds of different summer provenances and differences in their migratory patterns, highlighting key staging areas (Yalu River Estuary in China/North Korea for Dauria Region breeding birds, Daihai Lake for Central Mongolian and Ordos Basin for Western Mongolian birds). Based on this new knowledge of the biogeographical subpopulation structure of the Swan Goose, we need to combine data on subpopulation size, their distribution throughout the annual life cycle and conservation status, to develop more effective conservation strategies and measures to reverse population decline throughout the range.

Migratory herbivorous waterfowl track multiple resource waves during spring migration

“…Swan geese specialize on submerged tubers, which are only available when lakes have melted, although both field observations and our tracking data suggest swan geese can graze on sedges and grass (41,42). A former study observed that swan geese breeding in Eastern Mongolia (i.e., the same population as our study species) take significantly longer periods to arrive at their breeding grounds than those breeding in Central or Western Mongolian, due to a prolonged staging at the core stopover sites in the Northeast China Plain (43). Their arrival on the breeding grounds coincides with the date that minimum temperatures are above the freezing point of water (43).…”

The cascading effects of submerged macrophyte collapse on geese at Poyang Lake, China

“…Moreover, our study emphasises that food shortage may not only influence fitness of consumers through diet and foraging habitat shifts, but may also affect fitness of other animals through modification of interspecific interactions. Given the increasing important role of Poyang Lake in waterbird protection in the Yangtze River floodplain (Wang et al, 2017; Zhang et al, 2011) and the East Asian–Australasian Flyway (Damba et al, 2020; Deng et al, 2020; Li, Zhao, et al, 2020), it is urgent to reverse the broad decline of submerged macrophytes to protect waterbirds. Our study also emphasises the importance of behavioural plasticity for animals to cope with interspecific competition to respond rapidly to environmental changes.…”

“…It harbours about 420,000 waterbirds belonging to 111 species in winter (Li et al, 2019). Poyang Lake is one of the most important wintering grounds for geese, supporting about 90% of the inland population of the swan goose (Damba et al, 2020), about 50% of the East Asian population of the bean goose (Li, Zhao, et al, 2020), and 70% of the East Asian continental population of the greater white-fronted goose (Deng et al, 2020).…”

Habitat Suitability and Determinants for Anatidae in Multi-Watershed Composite Wetlands in Anhui, China

“…Simultaneously, establishing an Anatidae ecological monitoring network is essential. Regularly monitoring Anatidae numbers, distribution, and migration will enable prompt issue detection and the implementation of necessary conservation measures [53].…”