Gizzard and other lean mass components increase, yet basal metabolic rates decrease, when red knots Calidris canutus are shifted from soft to hard-shelled food

• Published in: Journal of Avian Biology
• Main Authors: Piersma, T, Gessaman, J A, Dekinga, A, Visser, G H
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2004
• Subjects: DISTANCE MIGRANT SHOREBIRD; BIRDS; SIZE; Calidris canutus
• Online Access: https://hdl.handle.net/11370/73d63856-7958-4475-8c45-4144c80942c7; https://research.rug.nl/en/publications/73d63856-7958-4475-8c45-4144c80942c7; https://doi.org/10.1111/j.0908-8857.2004.03259.x; https://pure.rug.nl/ws/files/6678152/2004JAvianBiolPiersma.pdf

We measured basal metabolic rate (BMR), body mass, lean mass, and gizzard mass of captive red knots Calidris canutus islandica maintained on a trout chow diet (soft-texture, low ash and water content) for several years and then shifted to small mussels Mytilus edulis (hard-texture, high ash and water content). During a 3-week period of feeding on mussels, body mass, lean mass, and gizzard mass increased 7.3 g (+7%), 10.5 g (+ 12%), and 4.9 g (+213%), respectively, yet BMR decreased from 0.96 to 0.89 W (- 8%). Under the new mussel regime, red knots must have reduced the metabolic intensity of some of the tissues. This suggests that the experimental red knots experienced the transition to a mussel diet as stressful and energy limiting, resulting in an energy-saving strategy by reducing BMR in spite of hypertrophy of the gizzard and other organs.