Abstracts

Q.3-12: Blood-lead concentrations in mottled ducks (Anas fulvigula) in the Louisiana Chenier Plain

Joseph R. Marty, Rockefeller Wildlife Refuge, Coastal and Nongame Resource Division, Louisiana Department of Wildlife and Fisheries, Grand Chenier, LA
Stephen K. McDowell, J.D. Murphree Wildlife Management Area, Texas Parks and Wildlife, Port Arthur, TX
Warren C. Conway, Department of Natural Resources Management, Texas Tech University, Lubbock, TX
Amanda French, School of Science, Faculty of Science and Engineering University of Waikato, Hamilton 3240, NZ

Presented by Joseph R. Marty - Email: jmarty@wlf.la.gov

The Western Gulf Coast is home to approximately 90% of the worldwide population of mottled ducks (Anas fulvigula), a nonmigratory species that must satisfy its annual cycle needs within a small geographic range. Population survey data suggest the Western Gulf Coast mottled duck population is experiencing declines in Texas and Louisiana. In Louisiana, coastal marsh and agricultural habitats are utilized by mottled ducks year round, yet these habitats are characterized by long traditions of waterfowl and other game-bird hunting, which potentially exposes mottled ducks to historical sources of lead persisting in the environment. Evidence suggests that mottled ducks and other waterfowl continue to ingest lead pellets despite strict shotshell regulations. In 2017, we collected blood samples (n = 124) from molting mottled ducks captured during banding efforts in Louisiana and from hunter-harvested mottled ducks during winter to determine blood lead and antimony concentrations. We found that 14% of mottled ducks contained elevated levels of lead (>200ppb), 1.5% contained toxic but sub-lethal levels of lead (500-1,000ppb), and no mottled ducks contained lethal levels of lead (>1,000ppb). We found no difference in lead concentration between age and sex of mottled ducks, and found a slightly negative, yet weak correlation between lead concentration (ppb) and body weight (g; R2 = 0.018). Lead and antimony isotope ratios showed correlation with lead shot exposure and all samples considered elevated had isotope ratios matching lead shot. Blood lead concentrations remain elevated in mottled ducks in Louisiana and Texas despite lead shot bans nearly 30 years ago. If lead levels in mottled ducks becomes an elevated concern, identifying habitats and areas where lead shot density and exposure is greatest would be an appropriate step towards reducing future threats. Additionally, identifying potential available sources of environmental lead will be important to minimizing this persistent threat to mottled ducks.