Investigating the association between diet and infection with Trichomonas gallinae in the European turtle dove (Streptopelia turtur)

Trichomonas gallinae, a protozoan parasite infecting a wide range of birds, has been a cause for conservation concern since its recognition as an emerging infectious disease, having had notable impacts on several avian species, including causing widespread mortality in greenfinches (Chloris chloris), and chaffinches (Fringilla coelebs), and hindering the recovery of the endangered pink pigeon (Nesoenas mayeri). Horizontal transmission between birds congregating at feeding sites, such as those provided for conservation and species management purposes, is an important driver in the spread of T. galliane. Supplementary feeding is a key conservation intervention for the European turtle dove (Streptopelia turtur), which is declining across its range, driven at least partially by a loss of natural food resources. Due to the link between T. gallinae transmission and supplementary feeding, we consider the prevalence of this parasite among European turtle dove in relation to diet, in the first study to analyze these two factors in the decline of this species together. Using birds sampled from breeding and wintering grounds, the dietary composition of individuals was compared to the presence of T. gallinae, and specific T. gallinae strains. Dietary variation was summarized into two axes using detrended correspondence analysis; neither was associated with the presence of T. gallinae or any specific strains. The proportion of diet accounted for by cultivated seeds did not affect parasite presence, despite the spread of this parasite being associated with supplementary feeding due to an increase in contact between potentially infected and uninfected birds gathering at high densities at feeding sites. Significant dietary overlap was observed between infected and uninfected individuals in all sites, with almost complete dietary overlap being observed in one breeding site. The level of dietary overlap between individuals infected with specific strains fluctuated between sampling seasons, indicating no consistent relationship between diet and infection status.