Higher rates of environmental contamination and site fidelity associated with increased prevalence of Salmonella enterica in urban American white ibis (Eudocimus albus)

While many wildlife species are unable to adapt to urban areas, others can be attracted to human resources, including species of conservation concern such as the American white ibis (Eudocimus albus). White ibis are... [ view full abstract ]

While many wildlife species are unable to adapt to urban areas, others can be attracted to human resources, including species of conservation concern such as the American white ibis (Eudocimus albus). White ibis are charismatic and regularly fed by the public in urban parks, promoting constant high bird densities which, in turn, may increase their exposure to pathogens if they regularly forage in urban areas. To test this hypothesis, in fall 2015 and spring 2016 we compared the movements and prevalence of Salmonella enterica shedding for 102 ibis captured in urban parks and wetlands in South Florida, 32 of which were fitted with GPS transmitters. Sampled ibis, soil, and water at urban parks had high Salmonella prevalence (71% of soil or water samples, 51% of birds) relative to wetlands (31% of soil or water, 28% of birds, p = 0.02). Ibis captured in urban parks also exhibited relatively higher rates of site fidelity by foraging in the same park (i.e. ≤1km of capture location for ≥4 hours during the day) for 71 ± 28% of days monitored and for 7 ± 2 hours per day. In contrast, ibis that foraged in wetlands traveled over larger areas and did not forage repeatedly near the capture location (i.e. ≤1km for 1.7 ± 0.8 of days monitored). During this period, the prevalence of Salmonella shedding in urban ibis was highly correlated with rates of water contamination at the urban park of capture (R2 = 0.87, p < 0.001). Our results suggest that higher site fidelity, likely from human feeding, coupled with higher rates of habitat contamination may lead to increased prevalence of environmentally-acquired pathogen infection for urban birds. Our results help to elucidate the effects of urbanization on wildlife health and can be used to mitigate the spread of zoonotic pathogens.