BRANTA — Jacquie A. Clark
Effects of severe weather on wintering waders
Institution: University of East Anglia, UK
Supervisors: WJ Sutherland, SR Baillie, (BTO)
Details: MPhil 2002 (Completed)
Address: British Trust for Ornithology, Thetford, U.K. IP24 2PU (Oct 2012) Email
Species Keywords: Dunlin Calidris alpina, Redshank Tringa totanus, Grey Plover Pluvialis squatarola
Severe winter weather, operating directly or indirectly, may cause increased mortality in waders in temperate zones. The level of mortality varies between species and also temporally and geographically. Redshank are particularly vulnerable to increased mortality in severe weather, Grey Plover have apparently become more vulnerable following population increase. The annual cycles of northern wintering waders take account of the possibility of severe weather. Waders increase in mass in winter presumably as an insurance against the chance of starvation. Maximum mass is probably a result of 'expected' temperature and feeding time available, mediated by predation. At the start of severe weather waders appear to be able to increase their mass, but in a severe or persistent severe period individuals may lose mass and some may die. The reduction in mass below that expected for the time of year may persist for over a month after the end of a particularly severe spell and could have implications for breeding success in the following summer. The waders which died in a severe weather period in February 1991 tended to be smaller than waders caught and measured in the ten years before the incident. Measurements of birds caught in the following ten years indicate that the size change did not persist in the populations.
Low winter temperatures coupled with unusual mortality in severe winter weather may have been an important factor controlling the numbers and distribution of wintering waders. With global warming, temperatures are rising and severe winter weather will become less frequent and wader populations may respond to this change. There is already a suggestion that the distribution of wader populations within Britain may be shifting north and east. There may be other consequences of climate change that will affect the numbers and distribution of waders wintering in Britain.
Clark, J.A. 2004. Ringing recoveries confirm high wader mortality in severe winters. Ringing & Migration 22:43-50.