Effects of feeding time constraints on body mass regulation and energy expenditure in wintering dunlin (Calidris alpina)

Abstract

We examined the effects of time-restricted feeding on regulation of body mass and activity energy expenditure in captive wintering dunlin (Calidris alpina) held in outdoor aviaries at Tomales Bay, California. In the first of two experiments, we compared birds under 24 h : 24 h (fasting : ad libitum feeding) food restriction with controls under continuous ad libitum feeding. In the second experiment, we compared birds under 24 h : 6 h : 12 h : 6 h (fasting : ad libitum : fasting : ad libitum) food restriction with birds under 24 h : 24 h food restriction. We estimated total energy expended on activities from daily mass balance using an additive model based on measures of gross energy intake, thermoregulation, basal metabolism, and a sensitivity analysis of gross utilization efficiency and energy density of reserve body tissue. Dunlin under 24 h : 24 h food restriction overcompensated for body mass lost while fasting, increasing their body mass relative to controls fed ad libitum. Dunlin under 24 h : 6 h : 12 h : 6 h food restriction were unable to recover body mass lost during the first fasting day. When allowed to feed, foodrestricted birds reduced the amount of energy spent on being active and increased food intake and energy storage relative to controls, but when forced to fast, they increased their activity energy expenditure. These patterns suggest winter body mass regulation consistent with the behaviors of free-living dunlin in winter. Key words: body mass regulation, Calidris alpina, dunlins, energy balance, food availability, metabolism, shorebirds, winter storms. [Behav Ecol 13:766–775 (2002)]