Brian Kearns, Ph.D Student
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
Location: Anahuac National Wildlife Refuge
Completion: August 2015
Status: Starting fall 2012.
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 the impacts of lead availability on survival and reproductive of mottled ducks.
(3) Evaluate the effect of lead on the body condition of mottled ducks
(4) Ratio of lead isotopes will be used to determine potential sources of lead in addition to spent lead short.
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.
Therefore, the proposed study will combine all of those data and conduct a formal
risk assessment of lead for mottled ducks. To determine potential source of lead
(i.e., natural or anthropogenic) in these samples, ratios of stable lead isotopes
following the methods of Saint-Laurent et al. (2010) will be evaluated. We will
use krieging techniques in ArcGIS along with general estimating equations to produce
maps for all NWRs that predict probability density functions of lead availability in
all sampled habitats across the range of mottled ducks. 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 will estimate the
effects of available lead on mottled duck survival and recruitment on the coast of
Texas. Recent efforts using population matrix models will be used to assess the
effects of lead exposure on reproduction and survival of mottled ducks. Finally,
these data will be used to conduct a risk assessment is the determination of the
quantitative or value of risk related to a concrete situation and a recognized
threat (also called hazard). Risk assessment consists in an objective evaluation
of risk in which assumptions and uncertainties are clearly considered and presented.
Part of the difficulty of risk management is that 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.