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I'm glad you have places to shoot pest birds and that you are going at them hard!! They do get educated pretty quickly though. My newest permission they smartened up quite a bit in just 30 minutes after dropping 8 of them if I remember correctly. I've not slowed my pace on them though as far as frequency of visits. I've just found that they don't let me get as close to them anymore. At one farm, I can't get closer than 75 yards to them.
A lot has to do with how much of a magnet the farm is to them. If there's grain there, then they will have a stronger desire to come back over and over. Same thing if they are nesting there. While they might fly off quickly, they will return quicker to a farm that has grain or a nesting sight than one they just transit, sort of like a rest stop. The Harvestor silos, the style with the railings, they're the best in that when a pigeon is on the railing, he's pretty much completely exposed for a shot. I don't worry about the domed ones.....the bigger concern is what's beyond that silo in the event of a miss. I've missed lots of birds on silos, so I always make sure I'm shooting in a safe direction. Normally there's nothing but open pasture or wooded area on the other side of the silo from the directions I choose to shoot from.
As far as damage to the domes.....I've hit them with 22 and 25 (pellets) and they bounce right off. Lets say the bird is sitting on the top and your shot goes low, the direction of the pellet and the very shallow angle of the dome will have it just skip right off. I've also put sighter shots on domed silos from say 75 yards and out, and the pellets just make a small dent. If you hit a dome at the base near where it meets the cement, and at 50 yds or less, there is definitely risk of penetration. Just don't shoot at them if they're sitting on a ledge near the base of the dome inside of 50 yds and you should be good.
A 25 caliber definitely hits harder, but a bad shot is a bad shot. I have a bunch of videos with the Wildcat 25 where I show some less than precise hits and they fly off like nothing. A solid hit is a solid hit whether it's a 25 or 22. I've killed more pigeons at 100+ yds with my 22 caliber rifles than with the Wildcat 25. Starlings are definitely small targets at 50 yds and further. Don't worry about missing them, just keep at them. Big thing is don't blink after the shot and you can most of the time see how much the pellet missed by. If you make the correct adjustment for your hold (or turret if you dial), you'll drill them after that. Before you know it you'll be drilling them further and further away.
Another important thing is to get as stable a rest as you can. If you can rest the rifle front and rear, whether you're on the roof/trunk/hood of your car, or on a table, your hit/miss ratio will improve. I don't take distance shots unless I have a stable rest. Prone is good too but it's difficult to make a shot at an elevated target while prone. Know your wind direction and use a ballistic calculator if you can. Strelok Pro is what I use....it's very accurate! And most of all keep making shots and try to learn from each miss or bad shot. There will always be misses and bad shots, it's just the way it goes. As good as they are, even Matt and Ted miss.
Keep at 'em buddy and I look forward to your vids!