, Volume 20, Issue 4, pp 635–642 | Cite as

Superpredation increases mercury levels in a generalist top predator, the eagle owl

  • Rui LourençoEmail author
  • Paula C. Tavares
  • Maria del Mar Delgado
  • João E. Rabaça
  • Vincenzo Penteriani


Superpredation can increase the length of the food chain and potentially lead to mercury (Hg) bioaccumulation in top predators. We analysed the relationship of Hg concentrations in eagle owls Bubo bubo to diet composition and the percentage of mesopredators in the diet. Hg levels were measured in the adult feathers of eagle owls from 33 owl territories in the south-western Iberian Peninsula, and in three trophic levels of their prey: primary consumers, secondary consumers and mesopredators. In addition, we studied 6,181 prey in the eagle owl diet. Hg concentrations increased along the food chain, but the concentrations in eagle owls showed considerable variation. The Hg concentration in eagle owls increased when the percentage of mesopredators in the diet increased and the percentage of primary consumers decreased. Superpredation is often related to food stress, and the associated increase in accumulation of Hg may cause additional negative effects on vertebrate top predators. Hg levels in these eagle owl populations are relatively low, but future monitoring is recommended.


Bioaccumulation Biomagnification Bubo bubo Intraguild predation Portugal Spain 



We thank M. Bassaler, S. Chollet, F. Goytre, and I. Prego for field assistance. C. Marques, S.M. Santos and two anonymous referees made useful comments on a previous version of the manuscript. R.L. was supported by a doctoral degree grant from Fundação para a Ciência e Tecnologia, Portugal (SFRH/BD/27434/2006). The work was funded by a research project of the Spanish Ministry of Science and Innovation (CGL2008-02871/BOS; with FEDER co-financing) and a grant from the Spanish Secretaría General de Universidades, Ministry of Education (Salvador de Madariaga Program)


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Copyright information

© Springer Science+Business Media, LLC 2011

Authors and Affiliations

  • Rui Lourenço
    • 1
    • 2
    Email author
  • Paula C. Tavares
    • 3
  • Maria del Mar Delgado
    • 1
    • 4
  • João E. Rabaça
    • 2
  • Vincenzo Penteriani
    • 1
    • 5
  1. 1.Department of Conservation BiologyDoñana Biological StationSevilleSpain
  2. 2.LabOr—Laboratory of Ornithology, Mediterranean Landscapes and Ecosystems Research Group, Institute of Mediterranean Agricultural and Environmental SciencesUniversity of ÉvoraÉvoraPortugal
  3. 3.CVRM-Geo-Systems Centre, Instituto Superior TécnicoLisbonPortugal
  4. 4.Laboratory of Ecological and Evolutionary Dynamics, Department of BiosciencesUniversity of HelsinkiHelsinkiFinland
  5. 5.Finnish Museum of Natural History, Zoological MuseumUniversity of HelsinkiHelsinkiFinland

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