Mottled Duck (Anas fulvigula) ecology in the Texas Chenier Plain Region

Many studies and plans have outlined the importance of the Chenier Plain Region of the Western Gulf Coast (WGC) to resident mottled ducks ( Anas fulvigula), including the Mottled Duck Conservation Plan and the Chenier Plain Initiative for the Gulf Coast Joint Venture. Currently, biologists have a relatively poor understanding of mottled duck habitat use, regional movements, response to habitat management, and movements. This information is needed to assist in strategic habitat conservation planning and to inform conservation for the species.;Factors limiting survival of WGC mottled ducks potentially include harvest, lead exposure, disturbance, habitat loss. or degradation, predators, and variations in climate patterns (Stutzenbaker 1988, Wilson 2007). We estimated cumulative weekly survival which allowed us to further define periods of relative high and low mortality, which will enabled us to compare our survival estimates to previous and ongoing studies. We employed known fate modeling in program MARK to assess the influence of potential mortality factors affecting mottled duck survival. Analyses indicate that survival rates remain below average for mottled ducks (12--38% annual rate of survival), when compared with other waterfowl species inhabiting the Gulf Coast. Primary periods of mortality included all periods of hunting and the molt biological time period. Drought conditions during 2011 also had negative impacts on overall survival rates of transmittered females. Conservation of quality coastal habitats remains a high priority to potentially offset current survival rates of mottled ducks.;Habitat use was measured by taking values for land cover and salinity from within the buffered areas (250 m) surrounding used points. Habitat use data were analyzed using an analysis of variance to assess differences among marsh type for year, time of day, and month. Habitat use was tied to salinity regime and water availability on the landscape with coastal marshes being selected for over adjacent ephemeral waters (e.g., stock tanks). Seasonal habitat selection varied based on average salinity and vegetative class within home ranges, with greatest sensitivity to salinity during breeding and brooding periods. Within season habitat use was extrapolated to identify potential high quality habitats based on local-scale selection patterns in the Texas Chenier Plain Region.;Habitat quality/quantity and disturbance were hypothesized to be important factors dictating mottled duck movements both spatially and temporally. Distance traveled, habitats used, and timing of movements by mottled ducks are widely unknown. Response to disturbance by mottled ducks inhabiting the upper Texas coast is also unknown. Because information on mottled duck movements is still widely unavailable, we documented weekly and seasonal movements of mottled ducks. In addition, we related variation in movement timing and distance with landscape habitat conditions (i.e., wetland availability), and disturbance.;The culmination of this research was development of a population demography model that spans the WGC Population of mottled ducks. The model was then evaluated based on available demographic rates (including data collected from this study). Following model validation, the relative importance/relatedness of various vital rates to the total population of WGC mottled ducks was assessed, and population persistence rates were calculated using IUCN criteria. Model simulations indicate that the probability of persistence to 100 years was 46%, with an average lambda = 0.383. Eighty of the 140 simulations reached quasi-extinction rates of ≥2500 individuals, and 77% of simulations met some IUCN criteria for the species to be listed as threatened, endangered or critically endangered. The model was sensitive to variation in all breeding parameters, which can be influenced by quality habitat management practices. As future population projections for the species are not improving and substantial habitat restoration efforts are needed to sustain and improve production for mottled ducks within the WGC Population. The model presented herein, assumes constant habitat conditions across time and does not incorporate future degradation of habitats. (Abstract shortened by UMI.).