I brought one of these a few years ago, then advertised as the whistler in my IAM magazine. Did it work ? We'll I can tell you that driving home in the small hours from work, Rabbits in the verge, pigeons and crows in the road did take flight as i approached them. Also witnessed by friends travelling in the car, I went on to Order a further 5 for them. I also fitted one to my klr 650 but it may have just been the noise from that that made them run. Won't work above 35mph I believe so that you can safely pass horses ect. .
