Wintering Behavior of Tundra Swan, Cygnus columbianus, at a Small Water-level Controlled Lake in the Middle and Lower Yangtze River Floodplain

The Tundra swan, Cygnus columbianus, wintering in the lakes of Yangtze River floodplain are facing wetland degeneration and habitat loss. Daily activity rhythm, time budget and foraging pattern of wintering swans are the important presentation of behavioral strategy in response to habitat variations. We studied the behavior of Tundra Swan wintering in the wetland of Huangpi Lake from November 2012 to February 2013. Wintering individuals and water levels were surveyed every day. Instantaneous scan and focal animal sampling was conducted to collect the behavior data. Foraging behavior is the major behavior in the wintering period, followed by rest behavior and vigilance behavior. In daily activity rhythms, the trough and peaks of foraging behavior appeared in the morning (09:00-10:00 h) and evening(16:00-17:00 h), which is just contrary to the rest behavior. Foraging and rest behaviors showed highly significant differences among all the daily time intervals (P<0.01). During the winter, the foraging and vigilance behaviors declined first, and then increased, which is contrary to the rest behavior. When the water level was lower in mid January, the time budget for vigilance behavior reached the lowest, amounting to 5.19 +/- 0.88%. There were significant or highly significant differences except for foraging time budget with the variation of water level. The foraging intensity was affected by water-level fluctuations, and declined with the increase in water level. When water level is low with more available food the swans assemble into a large flock and spend more time foraging, in the meantime the vigilance value declines so as to get enough food supply. Foraging intensity is lower in deep water and higher in shallow water. The small lake could be an alternative suitable foraging habitat for the wintering Tundra Swans when facing the habitat loss.

Automated summary

Wintering Tundra Swans in the lakes of the Yangtze River floodplain face wetland degeneration and habitat loss. The study found that foraging behavior dominates during the winter season, with troughs and peaks in the morning and evening. The foraging intensity and vigilance behavior of swans are affected by water level fluctuations, while shallow water areas are preferred for foraging.