+1 to Paco.
If you can land at one end or corner of the field they seem to feel less threatened, and avoid overflying them if you can. There must be enough room for them to get to a comfortable distance or they might try to go over/through the hedge.
Sheep, horses and cattle have never given me a problem at all.
Poultry is another matter, as are poultry farmers with a sniff of compensation for hundreds of "dead" birds...