Mercury Exposure Is Associated with Urbanization but not Salmonella Status in White Ibis (Eudocimus albus)

Matthew J Tatz; Stacey L Lance; Sonia M Hernandez

doi:10.7589/JWD-D-24-00002

Mercury Exposure Is Associated with Urbanization but not Salmonella Status in White Ibis (Eudocimus albus)

J Wildl Dis. 2024 May 17. doi: 10.7589/JWD-D-24-00002. Online ahead of print.

Authors

Matthew J Tatz^{1

2

3}, Stacey L Lance³, Sonia M Hernandez^{2

4

5

6}

Affiliations

¹ Odum School of Ecology, University of Georgia, 140 East Green Street, Athens, Georgia 30602, USA.
² Center for Integrative Conservation Research, University of Georgia, 210 River Road Suite 200, Athens, Georgia 30602 USA.
³ Savannah River Ecology Laboratory, University of Georgia, Savannah River Site Building 737-A, Aiken, South Carolina 29802, USA.
⁴ Daniel B. Warnell School of Forestry and Natural Resources, University of Georgia, 180 East Green Street, Athens, Georgia 30602, USA.
⁵ Southeastern Cooperative Wildlife Disease Study, Department of Population Health, University of Georgia, 589 D. W. Brooks Drive, Athens, Georgia, 30602, USA.
⁶ College of Veterinary Medicine, University of Georgia, 501 D. W. Brooks Drive, Athens, Georgia 30602, USA.

PMID: 38754863
DOI: 10.7589/JWD-D-24-00002

Abstract

Mercury (Hg) is a ubiquitous contaminant in wetlands that can cause immunosuppression in birds, which may increase susceptibility to colonization with Salmonella spp. Previously, we found that White Ibis (Eudocimus albus), a recently urbanized wading bird, shed Salmonella spp. at a higher prevalence when captured at urban sites, compared with natural sites. In this study, we sought to determine if Hg burdens in ibis are related to Salmonella status or degree of urbanization or both. We analyzed feathers from 94 ibis in Palm Beach County, Florida, USA, along an urbanization gradient (0-68% urbanization) and from individuals with confirmed Salmonella spp. status (shedding or not shedding). We detected Hg in all ibis feathers (0.22-8.47 mg/kg; mean=1.96 mg/kg; SD=1.94). The Hg concentration was not significantly correlated to Salmonella spp. shedding status (Wilcoxon rank sum test, W=1170; P=0.596) but was negatively associated with capture site urbanization level (R2=0.327; P=0.026). Our findings may suggest that the immunosuppressive effects of Hg do not affect Salmonella shedding in the ibis or that Hg burdens were too low to affect Salmonella shedding status. Further, ibis that were captured in high urbanization sites appeared to have a lower risk of Hg exposure than ibis that were captured within low urbanization sites.

Keywords: Eudocimus albus; Salmonella; Hg; White Ibis; mercury; urbanization.