Evol Ecol Res 3: 255-271 (2001)     Full PDF if your library subscribes.

Long-distance migrants as a model system of structural and physiological plasticity

Thomas P. Weber  and Anders Hedenström

Department of Animal Ecology, Ecology Building, University of Lund, S-223 62 Lund, Sweden

Author to whom all correspondence should be addressed.
e-mail: thomas.weber@zooekol.lu.se


Several migratory bird species show active cycles of hypertrophy and atrophy of nutritional organs and selected muscle groups. We develop a model for nutritional organs to identify the conditions under which such a pattern of structural change is optimal. Migrants may choose the size of two components of lean mass: a constant component that they carry throughout the entire migration period and a component just deposited during stopover. The benefit of depositing and subsequently discarding additional tissues in nutritional organs during stopover is an increased fuelling rate and a decrease in flight costs; the cost of hypertrophy and atrophy is a time cost.

 The predicted pattern depends strongly on the lean mass with which the migrants enter the migratory period. Time-selected migrants flying between widely separated stopover sites should show the highest degree of structural plasticity if they commence migration with a lean mass below maximum. If stopovers are possible everywhere along the migratory route, cycles of hypertrophy and atrophy are still possible but less likely.

 We also discuss the consequence of using different currencies in the optimization procedure. Only if duration of migration is a component of fitness can structural changes be expected. If the energy cost of transport is minimized, there is no unique prediction about active changes in lean mass. For short migration distances, it may be optimal to burn the lean mass deposited at the start of the stopover as fuel instead of discarding it before departure.

Keywords: avian migration, flight range, organ dynamics, stopover ecology, time minimization.

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        © 2001 2001 Anders Hedenström. All EER articles are copyrighted by their authors. All authors endorse, permit and license Evolutionary Ecology Ltd. to grant its subscribing institutions/libraries the copying privileges specified below without additional consideration or payment to them or to Evolutionary Ecology, Ltd. These endorsements, in writing, are on file in the office of Evolutionary Ecology, Ltd. Consult authors for permission to use any portion of their work in derivative works, compilations or to distribute their work in any commercial manner.

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