Plant chemistry and bird repellents

Research into chemical bird repellents is reviewed. The feeding preferences of Bullfinches Pyrrhula pyrrhula for bud extracts of 26 pear cultivars were established in the laboratory and correlated with underlying biochemical differences between extracts. A group of phenolic compounds was identified as aversive. Some of these compounds proved to be powerful inhibitors of protease activity in uitro , supporting theories about the role of phenolics as plant defences against herbivores. A larger study, however, failed to demonstrate a correlation between their biochemical reaction with digestive enzymes and their ability to deter feeding by feral pigeons Columba livia . Nevertheless, cinnamamide was identified as a promising bird repellent, although its mechanism of action is unclear.