I’m not sure what you mean by a wire predator guard ?
Best way I know is to not have a perch on the house and make sure entrance hole is 1 1/2 inches in diameter
Trapping is an option but very labor intensive-effective though!
Sparrow trapping is slow right now so I have been focusing on trapping the starlings instead
You might try a sparrow-spooker-not sure if it works on starlings and you have to be careful about timing so you don’t spook the bluebirds
Lots of good info at sialis.org
Good luck 🍀
Darrell in KC
