Digestive response to restricted feeding in migratory yellow-rumped warblers.
Smaller guts and slow initial mass gains at stopover sites have led to the idea that digestive physiology limits refueling rates in migrating birds. We tested the digestive-limitation hypothesis in yellow-rumped warblers using food restriction to simulate infrequent feeding during migration, which may cause a reduction in alimentary tract mass. Restricted birds had small intestine, pancreas, and liver masses 18%-22% lower than ad lib.-fed controls. Total activities of sucrase, maltase, aminopeptidase, and amylase were significantly lower in restricted birds, while those of trypsin and chymotrypsin were not. Only aminopeptidase mass-specific activity was significantly lower in restricted birds. Previously restricted birds were able to feed and digest at a high rate immediately following return to ad lib. feeding. Digestive efficiency did not differ between groups. These results suggest that before migration yellow-rumped warblers have some spare digestive capacity to compensate for declines in their digestive organ masses during migration.
Zoology Department, University of Wisconsin, Madison, WI, 53706, USA. kellylee@princeton.edu
Kelly A
KA
Lee
William H
WH
Karasov
Enrique
E
Caviedes-Vidal
D000222:Adaptation, Physiological; D025041:Animal Migration / Q000502:physiology*; D000818:Animals; D001835:Body Weight; D031204:Caloric Restriction; D004063:Digestion / Q000502:physiology; D004064:Digestive System / Q000033:anatomy & histology / Q000201:enzymology; D002149:Energy Intake; D004734:Energy Metabolism; D005247:Feeding Behavior; D005426:Flight, Animal; D008954:Models, Biological; D009929:Organ Size; D012621:Seasons; D020308:Songbirds / Q000033:anatomy & histology / Q000378:metabolism*