Common pest birds in the United States include the non-native European starling (Sturnus vulgaris), house sparrow (Passer domesticus), and the pigeon (Columba livia domestica), as well as native birds including Canada geese (Branta canadensis) and gull species (Laridae). Large concentrations of pest birds can create human health hazards and monetary losses due to consumption of crops, depredation, and fecal contamination and accumulation. Fecal contamination hazards include the potential spread of zoonotic diseases including antimicrobial-resistant zoonoses and human injury due to the accumulation of fecal material on walking surfaces. Additionally, fecal accumulation causes structural and aesthetic damage due to the accelerated deterioration of building materials and increased maintenance costs. Methods to alleviate hazards and damages from aggregations of pest birds are needed. In a series of 3 experiments conducted in Fort Collins, Colorado, USA, between 2016 and 2018, we evaluated 3 surface-application repellent formulations for the reduction of fecal accumulations due to European starlings: Airepel® HC with castor oil, an anthraquinone-based repellent; Airepel HC with castor oil without anthraquinone; and MS2, a novel inert formulation with a tacky, oily texture. We compared each formulation directly to an untreated control. All 3 formulations reduced fecal accumulations beneath treated aluminum perches as compared to fecal accumulations beneath untreated aluminum perches. Interestingly, both formulations that contained no anthraquinone worked equally well or better than Airepel HC with castor oil, the anthraquinone-based formulation. The benefits of an exclusively inert formulation include less risk to applicators and non-target species. Comprehensive experimental field testing of these surface-application repellent formulations is warranted
