Limited Access to Food and Physiological Trade-Offs in a Long-Distance Migrant Shorebird. I. Energy Metabolism, Behavior, and Body-Mass Regulation

• Published in: Physiological and Biochemical Zoology
• Main Authors: Vezina, Francois, Petit, Magali, Buehler, Deborah M., Dekinga, Anne, Piersma, Theunis
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2009
• Subjects: KNOTS CALIDRIS-CANUTUS; PECTORAL MUSCLE MASS; RED KNOTS; HEAT INCREMENT; NOCTURNAL HYPOTHERMIA; CLOSED ECONOMY; ZEBRA FINCHES; ORGAN SIZE; LEAN MASS; BIRDS; Calidris canutus
• Online Access: https://hdl.handle.net/11370/e335cc68-42b4-49f6-8b74-46ba52e249d3; https://research.rug.nl/en/publications/e335cc68-42b4-49f6-8b74-46ba52e249d3; https://doi.org/10.1086/603644; https://pure.rug.nl/ws/files/6736328/2009PhysiolBiochemZoolVezina2.pdf

Previous experiments showed reduction of basal metabolic rate (BMR) in birds facing energetic challenges. We alternately exposed two groups of red knots (Calidris canutus) to either 6 h or 22 h of food availability for periods of 22 d. Six h of access to food led to a 6%-10% loss of body mass over the first 8 d, with nearly all of the birds' daily energy expenditures supported by body nutrient stores during the first 2 d. Birds responded by increasing feeding behavior and food intake, but the response was slow. There were no gains of mass before day 15, which suggests a digestive bottleneck and a period of physiological adjustment. Food-restricted birds exhibited decreases in pectoral-muscle thickness and BMR in association with a loss of body mass. Although a decrease in BMR saves energy, savings represented only 2%-7% of the daily energy spent in excess of that acquired during the deficit period. Red knots did not downregulate mass-independent BMR. On the bases of recent independent findings and the pattern of mass gain observed when food access was switched from 6 h to 22 h, we suggest that these birds routinely maintain nutrient stores as a buffer against periods of energy shortages, thereby precluding the need for downregulation of mass-independent BMR.