A.Agincourt - you have a point, but I have found that helicopters of the medium to large variety or those with a noisy wang wang main rotor blades, ie: two main rotor blades DO frighten horses. Believe me I had children and a wife who rode and I was in the parrafin budgie. They do get used to it in part but a sudden noise from low flying aircraft of all sorts really get them going, and not always in the direction intended. I commend Janet Georges post as being very well written and thought out. If in doubt stay away from livestock of all kinds if you can, especially chickens! Boy do they learn to fly really quickly!