Effects of parasites and forest attributes on Chaffinches

Background/Question/Methods

The interaction of birds and their environment is complex. Human-induced changes of forest habitats should affect host-parasite-vector interactions. Changes in forest structure as well as the affects of parasites may influence bird populations. To better understand the interactions of vector-born parasites in habitat occupation of birds, we captured birds, took blood samples, stained (Giemsa) the slides and analyzed with Structural Equations Modeling (SEM) host-parasite interactions. We used the Chaffinch population (Fringilla coelebs) from the Schwäbische Alb exploratory, Southwest Germany, in 2011 and 2012 as model organism.

Results/Conclusions

(1) We found that first, forest structure explains parasite presence, second bird health condition. A light forest structure has indirect negative effects on parasitation, because vectors (Culicoides) avoid light but prefer dark areas and areas with water bodies.

(2) Parasites affect health condition of Chaffinches and parasites prevalence indicates chronic infection of birds and that Heterophils/Lymphocyte ratio indicates triggering of immune defense.

We conclude that parasites are affected indirectly through forest structure and vectors, but that vector-born parasites have themselves a significant effect on Chaffinches' habitat occupation.

See more of: Forest Habitats: Temperate
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