Klaassen M., Kersten M. & Ens B.J. (1990) Energetic requirements for maintenance and premigratory body mass gain of waders wintering in Africa. ARDEA 78 (1-2): 209-220

Daily food intake, assimilation efficiency and body mass were monitored in five species (Calidris canutus, C. alba, Arenaria interpres, Charadrius hiaticula, Numenius phaeopus) of waders kept in cages under tropical conditions. In three of these species the daily energy expenditure was measured using the doubly labeled water method. The energy content of the deposited reserve tissue depended on the condition of the birds, since the energy required for body mass gain was low in lean birds and high in fat birds. Maintenance metabolism was relatively low compared to wader species wintering in temperate regions. This phenomenon is suggested to be an adaptation towards reduced endogenous heat production, which may help in avoiding heat stress under tropical conditions. The reduced endogenous heat production hypothesis was supported by the finding that assimilation efficiencies of the tropical birds were low, which might have been caused by a reduced protein assimilation resulting in a relatively low heat increment of feeding. More direct support was the reduction in maintenance metabolism of Turnstones from the population wintering Africa compared to the maintenance metabolism of Turnstones from the population wintering in Europe, measured when the two groups were kept under identical conditions.