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Risk Assessment of Exposure to Lead for Mottled Ducks on National Wildlife Refuge of the Upper Texas Gulf Coast

Brian Kearns, Ph.D Student

Project Supervisors:
Dr. David Haukos
Dr. Warren Conway

U.S. Fish and Wildlife Service
U.S. Geological Survey

Texas Chenier Plain NWR Complex
Stephen F. Austin State University
Dr. Dan Collins
Patrick Walther

Location: Anahuac National Wildlife Refuge

Completion: August 2015

Status: Completed

Mottled ducks are being studied to determine potential impacts of lead exposure on populations of the Texas Gulf Coast

(1) Within the context of a formal risk assessment, evaluate the risk of environmental lead for mottled ducks and other waterbirds.
(2) Model factors determining lead availability and resulting mottled duck species distribution.
(3) Develop a body condition model for predicting non-breeding season fat stores in mottled ducks.
(4) Analyze lead isotope ratios in soil, vegetation, and mottled duck blood samples to determine past and ongoing sources of lead deposition.

Progress and Results:
Currently, ongoing studies on the Texas Chenier Plain and Midcoast NWR Complexes are quantifying spatial availability of lead pellets and lead concentrations in the soil, birds, and plants. In addition, that study is also relating environmental lead concentrations with concentrations in blood of mottled ducks and other species. This project combines all of those data in conjunction with unique analyses and data collection to conduct a formal risk assessment of lead exposure for mottled ducks. We used interpolation techniques in ArcGIS to produce maps for all NWRs that predict probability density functions of lead availability in all sampled habitats used by mottled ducks. To determine potential sources of lead in these samples (i.e., natural or anthropogenic), ratios of stable lead isotopes following the methods of Saint-Laurent et al. (2010) were evaluated and modelled spatially as well. Using the model being developed for predicting the influence of environmental lead on population demography of mottled ducks on the Texas Chenier Plain NWR, we have additionally estimated the effects of available lead on mottled duck species distribution using MaxENT models, which includes elucidation of landscape-level environmental covariates that may be contributing to lead "hot-spots" and where areas of increased lead concentration may overlap with areas of high mottled duck usage. This information may, in future, be used in conjunction with the non-breeding season fat index developed herein, which produced an equation that will allow managers to predict fat from age class, mass, and a length metric. Finally, these data will be used to conduct a cumulative risk assessment for lead exposure in these ecosystems, determining the quantitative value of risk related to a concrete situation and a recognized threat. Risk assessment consists of an objective evaluation of risk in which assumptions and uncertainties are clearly considered and presented. Part of the difficulty of risk management is the measurement of both of the quantities in which risk assessment is concerned - potential loss and probability of occurrence. The collected data will provide these quantities. We will follow the EPA framework for ecological risk assessment, including the following three general phases: (1) problem formulation, (2) analysis, and (3) risk characterization.

Kearns, Brian (Ph.D., 2015; advisor Haukos) Patterns and pathways of lead contamination in mottled ducks (Anas fulvigula) and their habitat, Kansas State University.

Kearns, B., P. Walther, W. Conway, and D. Haukos. 2014. A body condition index for non-breeding mottled ducks on the upper Texas Gulf Coast. Mottled Duck Symposium, Annual Conference of the Southeastern Association of Fish and Wildlife Agencies, Destin, Florida.

Brian Kearns, Stephen McDowell, Jena Moon, Elizabeth Rigby, and David Haukos. 2014. Identifying Landscape-level indicators of environmental contaminants that affect wildlife: a species distribution approach. Graduate Student Research Forum, Division of Biology, Kansas State University.

Kearns, B., P. Walther, and D. Haukos. 2014. Developing a body condition index for mottled ducks on the upper Texas Gulf Coast. Annual meeting of the Texas Chapter of The Wildlife Society, Austin, TX.

Kearns, B., S. McDowell, J. Moon, W. Conway, and D. Haukos. 2014. The legacy of lead: developing new methods for assessing lead contamination and wildlife exposure risks in Gulf Coast wetland habitats. Annual meeting of the Texas Chapter of The Wildlife Society, Austin, TX.

Kearns, B.V., McDowell, S., Moon, J., Rigby E., Haukos, D. 2014. Identifying landscape-level indicators of environmental contaminants that affect wildlife: a species distribution approach. Midwest Fish and Wildlife Conference, Kansas City, MO.

Kearns, B., D. Haukos, J. Moon, and E. Rigby. 2013. Species distribution in environmental decision-making: characterizing the efficacy of different models for use in habitat and wildlife management. Annual Meeting of the Society for Conservation GIS. Monterey, California.

Kearns, B., S. McDowell, J. Moon, and D. Haukos. 2013. Spatial analysis and ecological risk assessment for lead exposure in Gulf Coast waterfowl: does environmental lead represent an ecological trap? Annual Meeting of the Ecological Society of America. Minneapolis, Minnesota.