Climate and Other Human Causes of Spatial Variation in Mallard Mortality and Population Dynamics

(1) Wildlife population dynamics change across time and space, but few studies use formal spatiotemporal statistical models to understand these patterns. The population distribution of mallards (Anas platyrhyncos) in the Prairie Pothole Region (PPR) has shifted dramatically over the past several decades as agricultural intensity and climate have changed. (2) We examined spatiotemporal variation in survival, natural mortality, and harvest mortality rates for mallards in the PPR from 1974--2023 using intrinsic conditional autoregressive models in a Bayesian framework. (3) There was substantial variation over time and space for all demographic rates, and relationships between mortality and habitat variables varied by cohort. Specifically, environmental relationships indicate that habitats with less agricultural activity and more wetlands in breeding grounds may benefit dabbling duck populations via increased fecundity, but decrease survival via increased natural mortality driven by reproductive risks. Notably, non-spatially explicit models produced contradictory estimates for some parameters. (4) We also found a worrying trend: females exhibited declining survival probabilities across the time series. (5) Our analyses demonstrate major variation in survival rates of a well-studied organism across an environmental gradient, reveal subtle but critical differences relative to inference obtained from pooled data, and provide a clear roadmap to future research that can inform spatially-explicit conservation and management goals.