, Volume 135, Issue 4, pp 542–547 | Cite as

Parasite mediated mortality and host immune response explain age-related differences in blood parasitism in birds

  • Daniel SolEmail author
  • Roger Jovani
  • Jordi Torres
Population Ecology


An important pattern in host-parasite assemblages is a higher intensity of parasites in juveniles than in adults, but the reasons for these differences remain obscure. Three non-mutually exclusive hypotheses have been proposed: (1) heavily parasitized juveniles die before being recruited into the adult population ('selection' hypothesis); (2) the development of an acquired immunity by the host in front of the parasite reduces the intensity of the parasite in adult hosts ('immunity' hypothesis); and (3) differences in behavior makes adults less exposed to the parasite than juveniles ('vector exposure' hypothesis). Having rejected the 'vector exposure' hypothesis in a previous study, here we tested the 'selection' and 'immunity' hypotheses in feral pigeons (Columba livia) infected by the blood parasite Haemoproteus columbae. In agreement with the 'selection' hypothesis, young (but not adult) pigeons that were highly parasitized had a lower probability of surviving until adulthood, independent of their body condition. However, selection was not strong enough to account for the observed differences in parasite intensity between age-classes, and after selection parasite intensity of survivors still remained 85% higher in juveniles than in adults. In contrast, the 'immunity' hypothesis offered a greater explanatory power. The intensity of blood parasites in young pigeons, but not in adults, decreased over time so dramatically that by the time they had become adults their intensities were indistinguishable from that typically seen in adults. Therefore, while selection against highly parasitized juveniles can contribute to some extent to a reduction in parasitism seen in the adult population, age-specific blood parasitism in feral pigeons is best explained as a transitory phase just before the host develops an effective immune response.


Columba livia Haematozoa Haemoproteus columbae Parasite-host interaction Survival selection 



We thank D.M. Santos, M. Bosch, J. Garcia and D. Ventura for their assistance in the field. The paper was significantly improved with the valuable comments of D. Ryan, D. Reale, J.L. Tella, S.M. Reader and an anonymous referee. We specially thank J.D. Rodríguez-Teijeiro for his support and logistic assistance during the study, J. Champeny, L.l. Colom and F. Costa for the facilities given to work within the installations of the "Zoològic de Barcelona" and C. Pujol, J.D. Rodríguez-Teijeiro and L. Lefebvre for their constant support. This work was partially supported by a Québec Ministry of Education Postdoctoral Fellowship to D.S.


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Copyright information

© Springer-Verlag 2003

Authors and Affiliations

  1. 1.Department of BiologyMcGill UniversityMontrealCanada
  2. 2.Department of Applied Biology, Estación Biológica de DoñanaC.S.I.C. SevillaSpain
  3. 3.Departament de Microbiologia I Parasitologia SanitàriesUniversitat de Barcelona BarcelonaSpain

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