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1 April 2014 A Matrix Population Model for Mottled Ducks (Anas fulvigula) of the Western Gulf Coast
Elizabeth A. Rigby, David A. Haukos
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According to three surveys performed annually since the mid-late 1980s, the Anas fulvigula (Mottled Duck) population in Texas has declined substantially. Factors contributing to the observed trend are not well understood. Assessing the relative influence of vital rates on the population growth-rate is necessary to make management and conservation decisions regarding Mottled Ducks. We gathered estimates and associated variance estimates for vital rates of Mottled Ducks on the western Gulf Coast. We constructed a matrix population-model based on female vital rates and assumed birth-pulse reproduction, and parameterized it with a pre-breeding census. We calculated mean and standard error estimates for composite vital rates such as population growth rate (λ), fertility, and recruitment using 1000 iterations of the model. We also performed 20 meta-iterations of the population model to obtain mean coefficient of determination (r2) values for the linear regression of each vital rate and composite rates on λ. Overall λ was low, 0.541 (SE = 0.070). Fertility was also low, F = 0.071 (SE = 0.058). The elasticity analysis suggested that proportional changes in both fertility (r2 = 0.675) and survival (r2 = 0.322) played major roles in explaining the variation in λ. For the vital rates comprising F, breeding incidence (r2 = 0.270) and nest success (r2 = 0.200) explained the most variation in λ. Results indicated that the Mottled Duck population is in a steep decline, with low fertility and annual survival both influencing annual growth. We suggest targeting management efforts towards increasing adult survival, breeding incidence, and nest success for Mottled Ducks on the western Gulf Coast.

Elizabeth A. Rigby and David A. Haukos "A Matrix Population Model for Mottled Ducks (Anas fulvigula) of the Western Gulf Coast," Southeastern Naturalist 13(sp5), 26-40, (1 April 2014).
Published: 1 April 2014
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