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Urban sugar water feeding is associated with infection prevalence and body condition of visiting birds

Daria A. Erastovaa,*, Josie A. Galbraithb, Kristal E. Caina, Yolanda van Heezikc, Ellen Humea, Margaret C. Stanleya

aSchool of Biological Sciences, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand.;

bAuckland War Memorial Museum, The Auckland Domain, Parnell, Auckland 1010, New Zealand.

cDepartment of Zoology, University of Otago, PO Box 56, Dunedin 9054, New Zealand.

*Corresponding author (PhD student):

Despite the growing popularity of residential backyards sugar water bird feeding in New Zealand, the effect of this activity on wild birds remains understudied. One concern is that feeding stations can accumulate and favour infection transmission between individuals, negatively impacting visiting birds’ body conditions. This is the first study in New Zealand to investigate associations between sugar water feeder presence, city climate, season, sugar water concentrations and pathogenic, parasitic infections prevalence, body condition in urban birds. Birds caught in gardens with feeders had poorer body condition than gardens without feeders, but better body condition in the city with the warmer climate during summer and in gardens with higher sugar concentration feeders in winter. All screening tests for avian pathogens (C. psittaci and Salmonella spp.) returned negative results. Avian poxvirus prevalence in tauhou (Zosterops lateralis) was higher in the city with a warmer climate. The likelihood of lice infection in tauhou was lower in gardens with feeders than gardens without feeders but was lower in tauhou in the warmer city, in summer, and at feeders with higher sugar concentrations. In tūī (Prosthemadera novaeseelandiae), the likelihood of lice infection decreased with an increase in sugar concentration. Coccidia infection was higher in tauhou in gardens with feeders. The observed associations suggest that while there are potential benefits of winter sugar water feeding for native nectarivorous birds, sugar water feeding should be carried out cautiously, with attention to feeder type and hygiene to reduce infection transmission risks.