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Density-dependent productivity depression in Pyrenean Bearded Vultures: implications for conservation
Martina Carrete1, José A Donázar, Antoni Margalida
1Department of Applied Biology, Estación Biológica de Doñana (CSIC), Sevilla, Spain. martina@ebd.csic.es
Summary
Population growth in Bearded Vultures (Gypaetus barbatus) negatively impacts reproductive success. Conservation efforts should reconsider supplementary feeding due to its potential to decrease vulture productivity.
Area of Science:
- Conservation Biology
- Wildlife Ecology
- Population Dynamics
Background:
- Conservation programs aim to boost species populations by enhancing survival and reproduction.
- Density dependence in demographic parameters can complicate conservation strategies.
- The Bearded Vulture (Gypaetus barbatus) serves as a model species for studying population growth effects.
Purpose of the Study:
- To assess the impact of population growth on the reproductive performance of Bearded Vultures.
- To investigate the relationship between population size and demographic parameters.
- To evaluate the role of territorial quality and supplementary feeding in vulture population dynamics.
Main Methods:
- Analysis of a 25-year dataset on Bearded Vultures in Spain.
- Statistical modeling to assess the relationship between population size and reproductive output.
- Controlling for territorial heterogeneity and proximity to conspecifics and feeding points.
Main Results:
- Mean annual productivity of Bearded Vultures decreased significantly with increasing population size.
- Productivity was negatively correlated with the distance to nearest conspecific breeding pairs and supplementary feeding points.
- Site-dependency hypothesis supported: poorer territories are occupied as populations grow, reducing average productivity.
Conclusions:
- Bearded Vulture population growth is regulated by site-dependency, leading to decreased reproductive performance.
- Territory shrinkage and the presence of non-breeding individuals ('floaters') at feeding sites negatively impact productivity.
- Supplementary feeding strategies require re-evaluation due to potential negative effects on vulture reproductive success and unproven benefits for pre-adult survival.
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