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Ejaculate quality and the success of extra-pair copulations in the zebra finch


IN many passerine birds, sperm competition1,2 is intense and extra-pair paternity frequent3. The outcome of sperm competition is often determined by relative sperm numbers4,5, and theory predicts that males should maximize the number of sperm they ejaculate during extra-pair copulations6,7. Differences in sperm quality between males also affect the outcome of sperm competition4. Here we report that the swimming velocity of sperm of the zebra finch, Taeniopygia guttata, varies predictably within males, and is determined, together with sperm numbers, by the time since last ejaculation. By performing extra-pair copulations outside their own-pair copulation period, males maximize both the quality and number of sperm in ejaculates. These effects are a consequence of the way sperm are stored and mature in the male reproductive tract. The disportionate success of extra-pair copulations8, also seen in other birds9, may therefore be explained in terms of the independent effects of sperm numbers and velocity.

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  1. Parker, G. A. Biol. Rev 45, 525–567 (1970).

    Article  Google Scholar 

  2. Smith, R. L. (ed.) Sperm Competition and Evolution of Animal Mating Systems (Academic, London, 1984).

  3. Birkhead, T. R. & Møller, A. P. Sperm Competition in Birds: Evolutionary Causes and Consequences (Academic, London, 1992).

    Google Scholar 

  4. Martin, P. A. & Dziuk, P. J. J. Reprod. Fert. 49, 323–329 (1977).

    Article  CAS  Google Scholar 

  5. Martin, P. A., Reimers, T. J., Lodge, J. R. & Dziuk, P. J. J. Reprod. Fert. 39, 251–258 (1974).

    Article  CAS  Google Scholar 

  6. Parker, G. A. J. theor. Biol. 96, 281–294 (1982).

    Article  CAS  Google Scholar 

  7. Parker, G. A. Proc. R. Soc. B 242, 127–133 (1990).

    Article  ADS  Google Scholar 

  8. Birkhead, T. R., Pellatt, J. E. & Hunter, F. M. Nature 334, 60–62 (1988).

    Article  ADS  CAS  Google Scholar 

  9. Dixon, A., Ross, D., O'Malley, S. L. C. & Burke, T. Nature 371, 698–700 (1994).

    Article  ADS  Google Scholar 

  10. Pellatt, E. J. & Birkhead, T. R. Ibis 136, 97–101 (1994).

    Article  Google Scholar 

  11. Wolfson, A. Science 120, 68–71 (1954).

    Article  ADS  CAS  Google Scholar 

  12. Bedford, M. J. in The Spermatozoon, Maturation, Motility, Surface Properties and Comparative Aspects (eds Fawcett, D. W. & Bedford, M. J.). 7–21 (Urban & Schwazenberg, Baltimore, MD, 1979).

    Google Scholar 

  13. Moore, H. D. M. in Scientific Foundation of Urology (eds Chisholm, G. & Fair, W.) 399–410 (Heinemann Medical, Oxford, 1990).

    Google Scholar 

  14. Birkhead, T. R., Pellatt, E. J. & Fletcher, F. J. Reprod. Fert. 99, 593–600 (1993).

    Article  CAS  Google Scholar 

  15. Birkhead, T. R., Clarkson, K. & Zann, R. Anim. Behav. 35, 1853–1855 (1988).

    Article  Google Scholar 

  16. Birkhead, T. R. & Fletcher, F. Anim. Behav. 48, 451–456 (1994).

    Google Scholar 

  17. Shapiro, D. Y., Marconato, A. & Yoshikawa, T. Ecology 75, 1334–1344 (1994).

    Article  Google Scholar 

  18. Colegrave, N., Birkhead, T. R. & Lessells, C. M. Proc. R. Soc. B 259, 223–228 (1995).

    Article  ADS  Google Scholar 

  19. Wishart, G. J. & Palmer, F. H. Br. Poultry Sci. 27, 97–102 (1986).

    Article  CAS  Google Scholar 

  20. Wishart, G. J. & Steele, M. G. in Control of Fertility in Domesticated Birds (ed. Brillard, J. P.) 101–112 (INRA, Paris, 1990).

    Google Scholar 

  21. Lifjeld, J., Dunn, P. O., Robertson, R.J. & Boag, P. T. Anim. Behav. 45, 213–229 (1993).

    Article  Google Scholar 

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Birkhead, T., Fletcher, F., Pellatt, E. et al. Ejaculate quality and the success of extra-pair copulations in the zebra finch. Nature 377, 422–423 (1995).

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