Data from: Experimental feeding regime influences urban bird disease dynamics

Wild bird feeding often results in high densities of birds, potentially
facilitating transmission of disease. Wild birds are major reservoirs of
many zoonotic diseases, and although a number of avian disease outbreaks
have been linked to bird feeders, urban bird-feeding and its role in
disease systems remains poorly studied. We examined the impacts of typical
supplementary feeding practices on the health status of feeder-visiting
birds at experimental feeding stations in an urban area of New Zealand.
Over an 18-month period, we screened birds captured at feeding and
non-feeding properties for three pathogens and four groups of parasites to
determine whether feeding altered disease dynamics. We also assessed body
condition. All pathogens and parasites were detected in at least one
garden bird species. Feeding stations tested positive for Salmonella
enterica Typhimurium on ∼7% of occasions, confirming that structures used
in feeding are a potential transmission pathway. Feeding influenced some
parasite infection parameters; these effects varied among host species. In
silvereyes Zosterops lateralis, helminth prevalence and abundance were
lower at feeding properties compared to non-feeding properties. In
contrast, Eurasian blackbirds Turdus merula at feeding properties had a
higher abundance of helminths. House sparrows Passer domesticus at feeding
properties had a higher abundance of feather lice. Furthermore, our
feeding regime significantly affected body condition in house sparrow and
silvereye, though no associations between parasite parameters and body
condition indices were found. Our results demonstrate that feeding
practices can have varied effects on avian health, including no observable
effects for some disease agents in some host species. Disease risks are
present, however, thus understanding and reducing these risks should be a
key goal for all stakeholders to protect birds that use feeders and other
wildlife.