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Avian seed dispersal function is age dependent
Valentin Graf1,2, Martin U Grüebler3, Urs G Kormann3
1Senckenberg Biodiversity and Climate Research Centre, Frankfurt, Hessen, Germany.
Proceedings. Biological Sciences
|July 15, 2025
Summary
Juvenile spotted nutcrackers disperse pine seeds farther and at higher elevations than adults. This highlights age-related differences in animal contributions to ecosystem functions, crucial for forest regeneration.
Area of Science:
- Ecology
- Zoology
- Conservation Biology
Background:
- Animal species are vital for ecosystem functions.
- Individual variations in species' contributions to ecosystem functions are understudied.
- Spotted nutcrackers (Nucifraga caryocatactes) are key seed dispersers for Swiss stone pine (Pinus cembra).
Purpose of the Study:
- To investigate how age (juvenile vs. adult) affects seed dispersal by spotted nutcrackers.
- To compare seed dispersal ranges, displacement variability, and caching elevations between juvenile and adult birds.
- To understand ontogenetic shifts in seed dispersal function.
Main Methods:
- Tracking of 72 juvenile and adult spotted nutcrackers.
- Comparison of seed dispersal ranges, hourly displacement, and elevation of occurrence.
- Analysis of seed caching elevations.
- Longitudinal tracking of nine individuals over two years.
Main Results:
- Juveniles exhibited significantly larger seed dispersal ranges and higher displacement variability than adults.
- Juveniles occurred and cached seeds at higher elevations compared to adults.
- Birds showed reduced dispersal ranges but maintained similar displacements and elevational occurrence from juvenile to adult stages, indicating ontogenetic shifts.
Conclusions:
- Juvenile spotted nutcrackers play a critical role in pine seed dispersal due to their extensive ranges and higher elevation activity.
- Age-dependent variations in animal dispersal functions are essential for assessing ecosystem services.
- Understanding these age effects is vital for predicting forest regeneration under climate change.
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