Urbanization, food provisioning, and transmission-relevant behaviors in Florida white ibis

Cali A. Wilson, Julia N. Weil, Sonia Altizer and Richard J. Hall, Odum School of Ecology, University of Georgia, Athens, GA, Cali A. Wilson, Sonia Altizer and Richard J. Hall, Center for the Ecology of Infectious Diseases, University of Georgia, Athens, GA, Sonia M. Hernandez, Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA, Richard J. Hall, Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, GA

Background/Question/Methods
As urban areas expand and natural habitats shrink, many wildlife species have shifted into cities and suburbs, where they commonly encounter human-provided food. In acclimating to urban areas, animals often aggregate at higher density, move less, alter their diets, and encounter anthropogenic stressors, all of which can affect the transmission of infectious diseases. For example, aggregation can increase exposure to directly-transmitted parasites, but reduced time spent searching for food could lower exposure to environmentally-acquired parasites. American white ibis (Eudocimus albus) in South Florida are well-suited for studying the consequences of urban living on pathogen transmission. Ibis naturally forage in wetlands but now commonly reside in urban parks, where they exploit human-provided food. In this study, we investigate how transmission-relevant ibis behaviors change between urban and natural sites, across urban sites along a gradient of provisioning, and when ibis are actively fed in urban parks. To test the hypothesis that urban ibis spend less time foraging than natural ibis, we observed flocks at 3 wetland sites and 3 urban parks. We also conducted 10-minute focal follows at 5 urban sites along a gradient of food provisioning, and quantified flock density changes during anthropogenic feeding events in urban parks.
Results/Conclusions
Ibis in urban parks spent less time actively foraging relative to those in natural wetlands. Within urban sites, foraging, preening, and vigilance behaviors differed across the sites observed. Birds at two of the urban sites foraged less, on average, than those at other sites, but spent significantly more time either preening or being vigilant. Preliminary results suggest this trade-off could be due to differences in the level of human-provided food at urban sites. Lastly, during feeding intervals, ibis density increased by over 20 times each time food was thrown to the birds. These results suggest that urbanization and resource provisioning alter wildlife behavior in ways that can influence exposure to parasites. Specifically, in ibis, food provisioning in urban parks can increase local density and contact rates for transmission of directly transmitted parasites, while simultaneously decreasing exposure to environmentally-transmitted parasites due to lower active foraging time. Further studies of how urbanization and recreational feeding influences wildlife behavior can inform management strategies to benefit both wildlife and human health.