European starlings (Sturnus vulgaris) are a known risk factor for the occurrence of microorganisms that are pathogenic to cattle and humans in concentrated animal feeding operations (CAFOs). Starling use of CAFOs is known to vary in response to weather; starling control operations on CAFOs often are timed to coincide with favorable environmental conditions to maximize take. The totality of this information suggests that disease risks in CAFOs associated with starlings may be influenced by environmental factors, such as temperature. In this study, we assessed the risk of Salmonella enterica contamination of cattle feed by modeling the interaction between starling numbers and ambient air temperatures using data previously reported from Texas CAFOs. We compared these interaction models to the previously published additive models for S. enterica contamination of cattle feed using an information-theoretic approach to model selection that ranked and weighted models in terms of their support by the data, using bias-adjusted Akaike’s Information Criterion (AICc) and Akaike weights (Wi). Our results indicate that the interaction between European starlings and ambient air temperature better explained the occurrence of S. enterica in cattle feed than any of the previously reported models. Specifically, the risk of S. enterica contamination of cattle feed by starlings was greatest when winter temperatures were highest (10°C). Thus, we conclude that the risk of S. enterica contamination of cattle feed by starlings will be worst on the few winter days when daytime high temperatures are above freezing and large numbers of birds are present. Because these conditions will be most common in the late winter and early spring, we recommend that starling control operations on feedlots and dairies be conducted as early in the winter as possible to mitigate the risks of disease created by large foraging flocks of starlings
