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Immunological indices and parasites in blackbirds

Cite this dataset

Moreau, Jérôme (2021). Immunological indices and parasites in blackbirds [Dataset]. Dryad.


1. Despite the intensive use of immune indices in immunoecology, whether to interpret the results of immune indices in terms of actual immune competence (i.e., ability to control and clear parasite infections as indicated by high values of immune indices associated with low parasite loads) or current immune activation (pathogenic infection being associated with high parasite load and high values of immune indices) is still an open question. Most studies to date have produced contrasting results focused on the effect of a single parasite species despite the fact that hosts usually harbour a community of parasites that influence one another’s impact on host immune response.

2. We simultaneously assessed blood parasites, intestinal parasites and ectoparasite loads in male blackbirds and compared these measures to several immune indices to investigate how parasites explain the variation around the mean of these immune indices.

3. Parasite loads covaried within hosts. Immune indices better reflected the interacting effects of these parasites than the independent effect of each parasite. Immune indices may therefore be better indicators of ongoing pathogenic infections than immune competence. Furthermore, intestinal parasites explained a significant part of the variance in most immune indices through their interactions with other parasites, suggesting that they have a strong influence in modulating immune function.

4. Taking the parasite community into account in immunoecology studies will certainly help increase our understanding of immune indices.


Fifty adult male blackbirds were caught using mist-nets in four major urban parks in Dijon, France. For each bird, we assesed the number of ectoparasites, the number of blood parasites and intestinal parasites. After that, we assesed immunological indices with a blood sample.