Survival of Shorebirds (Charadrii) During Severe Weather: The Role of Nutritional Reserves

Abstract

During winter, shorebirds face increasing difficulty in achieving sufficient rates of prey intake to satisfy their energy requirements, as a result of the deterioration in environmental conditions. The effects of severe winter weather are twofold. Firstly, invertebrate prey species living in muddy or sandy substrata often become less available to shorebirds, either because they become less active and so less detectable, or by lying deeper in the substratum, mainly in response to low temperatures, and also to high winds (Smith, 1975). These changes in prey availability, and the responses to them by shorebirds, are discussed by Evans (1979) and Pienkowski (1980a, and this volume). The responses by shorebirds involve changes mainly in foraging behaviour and/or in prey species taken (Goss-Custard, 1969; Smith, 1975; Evans, 1976; Davidson, unpublished). The second, direct, effect of severe weather on shorebirds is to increase the energetic costs of thermoregulation during periods of low temperatures and high winds. Gales can also affect shorebirds directly by preventing them from feeding on their preferred feeding grounds (Evans, 1976; Dugan et al.,in press).