Keep trying !

See it from their point of view; Would you let someone you didn't know wander around your land with a gun.

It might help if you look at the land first and personalise it. " I've noticed that your fields of crops have extensive rabbit/pigeon damage....."
"I notice that you have numerous pigeons on your barns which are likely to contaminate livestock feed"

I'm sure you'll get something in the end.

Dave E