Diet quality and food limitation affect the dynamics of body composition and digestive organs in a migratory songbird (Zonotrichia albicollis).
Migrating songbirds interrupt their feeding to fly between stopover sites that may vary appreciably in diet quality. We studied the effects of fasting and food restriction on body composition and digestive organs in a migratory songbird and how these effects interacted with diet quality to influence the rate of recovery of nutrient reserves. Food limitation caused white-throated sparrows to reduce both lean and fat reserves, with about 20% of the decline in lean mass represented by a decline in stomach, small intestine, and liver. During refeeding on diets similar in nutrient composition to either grain or fruit, food-limited grain-fed birds ate 40% more than did control birds, and they regained body mass, with on average 60% of the increase in body mass composed of lean mass including digestive organs. In contrast, food-limited fruit-fed birds did not eat more than did control birds and did not regain body mass, suggesting that a digestive constraint limited their food intake. The interacting effects of food limitation and diet quality on the dynamics of body composition and digestive organs in sparrows suggest that the adequacy of the diet at stopover sites can directly influence the rate of recovery of body reserves in migrating songbirds and hence the pace of their migration.
Department of Natural Resources Science, University of Rhode Island, 105 Coastal Institute Kingston, Kingston, Rhode Island 02881, USA. bjpierce2@yahoo.com
Barbara J
BJ
Pierce
Scott R
SR
McWilliams
D000704:Analysis of Variance; D025041:Animal Migration / Q000502:physiology*; D000818:Animals; D001823:Body Composition / Q000502:physiology*; D001835:Body Weight; D004032:Diet; D004064:Digestive System / Q000033:anatomy & histology; D004553:Electric Conductivity; D005508:Food Deprivation / Q000502:physiology*; D012237:Rhode Island; D020308:Songbirds / Q000502:physiology*