Is Long‐Distance Bird Flight Equivalent to a High‐Energy Fast? Body Composition Changes in Freely Migrating and Captive Fasting Great Knots

We studied changes in body composition in great knots,Calidris tenuirostris, before and after a migratory flight of 5,400 km from northwest Australia to eastern China. We also took premigratory birds into captivity and fasted them down to their equivalent arrival mass after migration to compare orga...

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Bibliographic Details
Published in:Physiological and biochemical zoology 2001-05, Vol.74 (3), p.435-449
Main Authors: Battley, Phil F., Dietz, Maurine W., Piersma, Theunis, Dekinga, Anne, Tang, Sixian, Hulsman, Kees
Format: Article
Language:English
Subjects:
Adipose tissues
Aerial locomotion
Analysis of Variance
Animal migration behavior
Animals
Animals, Domestic
Animals, Wild
Australia
Average linear density
Birds
Birds - anatomy & histology
Birds - physiology
Body Composition
Body Weight
China
Energy Metabolism
Fasting
Fasting - physiology
Flight, Animal - physiology
Intestines
Legs
Organ Size
Wild birds
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Summary:We studied changes in body composition in great knots,Calidris tenuirostris, before and after a migratory flight of 5,400 km from northwest Australia to eastern China. We also took premigratory birds into captivity and fasted them down to their equivalent arrival mass after migration to compare organ changes and nutrient use in a low‐energy‐turnover fast with a high‐energy‐turnover fast (migratory flight). Migrated birds were as economical as any fasting animal measured yet at conserving protein: their estimated relative protein contribution (RPC) to the energy used was 4.0%. Fasted birds had an estimated RPC of 6.8% and, consequently, a much lower lean mass and higher fat content for an equivalent body mass than migrated birds. Lean tissue was catabolized from most organs in both groups, except the brain. Furthermore, a principal components biplot showed that individuals were grouped primarily on the basis of overall organ fat or lean tissue content rather than by the size of specific organs. This indicates that organ changes during migratory flight are similar to those of a low‐energy fast, although the length of the fast in this study probably accentuated organ reductions in some functional groups. Whether the metabolic characteristics of a flying migratory fast follow the three‐phase model described in many inactive fasting animals is unclear. We have some evidence for skeletal fat being catabolized without phase 3 of a fast having been reached.
ISSN:1522-2152
1537-5293
DOI:10.1086/320432