Winter drought affects wetland habitat quality and extent, impacting the distribution, body condition and ultimately the fitness of migratory waterbirds that depend upon such habitats for food resources. Extreme drought at Poyang Lake, China, in 2022 caused the lowest water levels there since 1956. We compared daily movement distance, home range, habitat utilization and arrival/departure dates of the same eight wintering Greater White‐fronted Geese Anser albifrons at Poyang Lake during two consecutive winters with contrasting water levels, 2021/22 (a normal year) and 2022/23 (severe drought year) using GPS tracking data. Compared with the normal year, the home range (95% isopleth) increased significantly (by 58%), and the percentage use of cropland and other non‐wetland habitat types increased more than 30‐fold in the drought year. Although the core area size (50% isopleth) used by the geese in the drought year did not differ significantly, the proportion of time spent in wetlands decreased compared to that in the normal year. Home range area tended to increase and then decrease successively through both winters. Greater White‐fronted Geese left their wintering grounds 13 days later in the drought year than in the normal year, timing seemingly unaffected by prevailing temperature or tailwinds. It would therefore seem that Greater White‐fronted Geese adapted to the environmental changes caused by drought by showing more exploratory behaviour, expanding their home range and adjusting their habitat use, rather than depart the Poyang Lake area. However, the adverse conditions could have contributed to their delayed departure, extending their wintering duration, implying the energetic benefits of shifting to cropland for foraging was insufficient to attain body condition needed for migration as early as in other years. This study shows how extreme weather conditions can affect the behaviour of migratory waterbirds, which potentially may have fitness consequences, which requires further research to confirm.
Wang et al. (Sun,) studied this question.