Effect of an ultrasonic device on the behaviour and the stress hormone corticosterone in feral pigeons.
The worldwide presence of feral pigeons Columba livia domestica in urban habitats presents potential public health hazards from pathogens and parasites, and droppings can lead to damage to buildings. A variety of lethal and non-lethal chemical repellents, visual, sonic or mechanic measures are available to deter pigeons, but they are not always applicable or effective. Ultrasonic devices are one of the available possibilities with the advantage of being inaudible to humans and more or less harmless to animals. However, their utility is questionable, because the upper limit of frequencies heard by pigeons reported is well below that of ultrasound. We tested whether a commercially used ultrasound deterrent system has an effect on the behaviour of free-living, as well as caged feral pigeons and assessed whether ultrasound has a physiological effect, i.e. whether it can activate the hypothalamo-pituitary-adrenal-axis (HPA-axis) known to trigger flight behaviour. Our experimental tests did neither show any effect on the behaviour and the HPA-axis of the caged pigeons nor any deterring effect on the free-living pigeons. A habituation effect could not be detected. We therefore, conclude that ultrasound does not deter feral pigeons.