Foraging behavior of European starlings: implications for mitigating their impact on native species

Abstract

European starlings (Sturnus vulgaris) are a remarkably successful invasive species known to compete with native bird species for nest sites. The objective of this study was to understand why starlings avoid ungrazed pastures and provide recommendations to help mitigate the impacts of starlings on native bird species. I used aviary trials to examine the effects grazing and mowing practices on starling foraging behavior. In experiment 1, I examined the effects of grass height and litter. Starlings preferred to forage in short grass without litter. In Experiment 2, I modified the treatments to more closely simulate actual grazing and mowing practices. Results further confirmed avoidance of areas with tall grasses. Starlings entered all three of the mowed treatments more than the control treatment. No preference was found for the treatment representing long-term exclusion of grazing, therefore a single year of exclusion from grazing or mowing appears sufficient to deter foraging by starlings. Short grass and lack of litter likely facilitate increased mobility, increased ability to detect and capture prey, and increased visibility to see potential predators. Recommendations include leaving moderate or high levels of forage in areas where starlings prefer to forage, such as moist swales and level, open woodlands. Because distance to foraging sites has been found to be negatively correlated with nesting density, competition with native species for nest cavities may be decreased by reducing the quality of foraging habitat. Rotational grazing that creates a mosaic of varying grass heights might offer opportunities for reducing starling densities. In exurban areas, avoidance of extensive mowed and watered lawns that attract starlings is recommended. Further research is needed to investigate thresholds of grass height at which starlings are discouraged from foraging. A species as numerous as the starling almost certainly has impacts beyond the guild of cavity-nesting birds. Interspecific relationships among ground-foraging insectivores should be investigated in areas where native bird species co-occur with starlings.

Parent Publication

• Proceedings of the seventh California oak symposium: managing oak woodlands in a dynamic world

Citation

Purcell, Kathryn L. 2015. Foraging behavior of European starlings: implications for mitigating their impact on native species. In: Standiford, Richard B.; Purcell, Kathryn L., tech. cords. Proceedings of the seventh California oak symposium: managing oak woodlands in a dynamic world. Gen. Tech. Rep. PSW-GTR-251. Berkeley, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station: 73-81.