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
.22 Webley Vulcan; .177 BSA MS Hornet; .177 FX Cyclone; 4 x .177 Gamo Delta's; .177 Brocock Hunter thumbhole stock; .177 Brocock Hunter Sporter.