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Flexible seasonal timing and migratory behavior: results from stonechat breeding programs
Barbara Helm1, Eberhard Gwinner, Lisa Trost
1Max Planck Institute for Ornithology, von-der-Tann-Str. 7, D-82346 Andechs, Germany. helm@orn.mpg.de
Annals of the New York Academy of Sciences
|August 2, 2005
Summary
Long-distance migratory birds exhibit flexible life cycle timing, not rigid schedules. Their apparent rigidity stems from short breeding seasons and inflexible molt onset, crucial for timely departure.
Area of Science:
- * Ornithology
- * Behavioral Ecology
- * Evolutionary Biology
Background:
- * Migratory syndromes in birds are thought to involve rigid seasonal schedules.
- * Stonechats (passerines) exhibit diverse migratory behaviors and schedules across Europe, Africa, and Siberia.
- * Previous studies suggest a link between migratory distance and schedule inflexibility.
Purpose of the Study:
- * To test the hypothesis that long-distance migrants have rigid schedules.
- * To investigate the temporal plasticity of life cycle stages in stonechats with varying migratory strategies.
- * To understand the mechanisms underlying apparent schedule rigidity in migratory birds.
Main Methods:
- * Comparative study of European, African, and Siberian stonechat subspecies in captivity.
- * Monitored endogenous cycles of reproduction and molt under controlled aviary conditions.
- * Analyzed differences in timing of breeding, molt, and premigratory preparations (Zugunruhe).
Main Results:
- * All stonechat subspecies showed endogenous cycles but differed in life stage timing flexibility.
- * African stonechats were multibrooded, while Siberian stonechats raised single broods, linked to breeding window length.
- * Premigratory molt timing varied; Siberian stonechats initiated it earlier, while European and African subspecies' timing depended on hatching date.
Conclusions:
- * Apparent rigidity in long-distance migrant schedules is linked to short breeding cycles and inflexible molt onset, not reduced plasticity.
- * Short breeding and development windows may ensure timely departure for migration.
- * Temporal plasticity in stonechats is organized differently, not reduced, and can be enhanced by modifying environmental conditions for program expression.
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