Sperm Length Variation as a Predictor of Extrapair Paternity in Passerine Birds

• Jan T. Lifjeld ,

  * E-mail: j.t.lifjeld@nhm.uio.no

  Affiliation National Centre for Biosystematics, Natural History Museum, University of Oslo, Oslo, Norway

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• Terje Laskemoen,

  Affiliation National Centre for Biosystematics, Natural History Museum, University of Oslo, Oslo, Norway

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• Oddmund Kleven,

  Affiliation National Centre for Biosystematics, Natural History Museum, University of Oslo, Oslo, Norway

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• Tomas Albrecht,

  Affiliation Department of Population Biology, Institute of Vertebrate Biology, Academy of Sciences of the Czech Republic, and Department of Zoology, Faculty of Science, Charles University in Prague, Brno, Czech Republic

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• Raleigh J. Robertson

  Affiliation Department of Biology, Queen's University, Kingston, Ontario, Canada

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