Necessity spawns plasticity: Siberian Cranes abandon specialist foraging behaviors after an extreme flood event
Every year, hundreds of thousands of migratory waterbirds travel to Poyang to spend the winter months foraging and building up fat reserves for the return migration north in the spring. Poyang Lake is a dynamic wetland system with dramatically fluctuating water levels: high in the summer and low in the winter. When water levels recede in the fall, it uncovers seasonal meadows, mudflats and shallow, pothole lakes, creating a wide range of habitat for hundreds of migratory waterbird species. Typically, Siberian Cranes, Tundra Swans and Swan Geese depend on the shallow lakes at Poyang where they usually forage for below-ground tubers and rhizomes of the water plant Vallisneria. During his most
Burnham believes that a summer flood event in 2010 is the main culprit behind these new habitat use patterns and behaviors. The 2010 flood was the worst to hit Poyang since devastating floods ravaged the area in 1998, killing thousands and causing billions in damage. Unlike the post-flood behavior Burnham observed in 2010-2011, however, observers in the winter of 1998-1999 recorded the water birds feeding in their typical foraging habitats in and around the pothole lakes. Burnham has a two-part hypothesis to explain why the birds behaved so differently following the 2010 flood: 1) the flood occurred early in the Vallisneria growing season, before the plant could become widely established across the lake basin, and 2) new aquaculture practices, such as crab farming, removed Vallisneria that had been present in un-flooded areas in previous years. Burnham is working with multiple partners from China, the United States and Europe to help him put together the pieces of this puzzle.
Burnham feels that the shift from one food resource to another by the cranes, swans and geese will provide important insight into how the birds will respond to future extreme events. Poyang continues to be a dynamic wetland: this spring, the lake experienced an abnormal drought and water levels were at some of the lowest levels ever recorded. Whether this latest extreme event will affect the migrants remains to be seen, but Burnham looks forward to investigating how this latest puzzle piece changes the picture at Poyang.