Associations of Forest Type, Parasitism and Body Condition of Two European Passerines, Fringilla coelebs and Sylvia atricapilla

Bruntje Lüdtke,Diego Santiago-Alarcon,H Martin Schaefer,Isabelle Moser,Marcela Suarez-Rubio,Swen C Renner,Marco Tschapka,Elisabeth Kv Kalko,Markus Fischer,Csaba Moskát

doi:10.1371/journal.pone.0081395

Abstract

Human-induced forest modification can alter parasite-host interactions and might change the persistence of host populations. We captured individuals of two widespread European passerines (Fringilla coelebs and Sylvia atricapilla) in southwestern Germany to disentangle the associations of forest types and parasitism by haemosporidian parasites on the body condition of birds. We compared parasite prevalence and parasite intensity, fluctuating asymmetries, leukocyte numbers, and the heterophil to lymphocyte ratio (H/L-ratio) among individuals from beech, mixed-deciduous and spruce forest stands. Based on the biology of bird species, we expected to find fewer infected individuals in beech or mixed-deciduous than in spruce forest stands. We found the highest parasite prevalence and intensity in beech forests for F. coelebs. Although, we found the highest prevalence in spruce forests for S. atricapilla, the highest intensity was detected in beech forests, partially supporting our hypothesis. Other body condition or health status metrics, such as the heterophil to lymphocyte ratio (H/L-ratio), revealed only slight differences between bird populations inhabiting the three different forest types, with the highest values in spruce for F. coelebs and in mixed-deciduous forests for S. atricapilla. A comparison of parasitized versus non-parasitized individuals suggests that parasite infection increased the immune response of a bird, which was detectable as high H/L-ratio. Higher infections with blood parasites for S. atricapilla in spruce forest indicate that this forest type might be a less suitable habitat than beech and mixed-deciduous forests, whereas beech forests seem to be a suboptimal habitat regarding parasitism for F. coelebs.

Highlights

Animals interact with their environment in complex ways and can respond, for example, to changes in forest structure and parasite infections [1,2,3]
Forest type and parasitism in birds Mean parasite prevalence and parasite intensity differed between F. coelebs and S. atricapilla (Table 1); these parameters were different within each bird species with reference to forest type (Table 1)
Forest type and parasitism Contrary to our expectations, we found that all parasite population parameters were higher for both bird species captured at beech and mixed-deciduous forests, except for prevalence in S. atricapilla, which was higher in spruce forests

Summary

Introduction

Animals interact with their environment in complex ways and can respond, for example, to changes in forest structure and parasite infections [1,2,3]. Whether animals select a habitat influenced by intra- and inter-specific interactions [4,5], such as parasitism, is not yet fully understood. Indirect effects of parasites include altering habitat selection processes of hosts [10], modifying coexistence of species (e.g., [3]), changing host behavior [11], or structuring of animal communities [12]. Costs associated with parasitism could drive birds away from places with high infection risk; the role of forest types on host-parasite interactions is not yet rigorously investigated

Methods

Results

Conclusion