Nestbox portal protector - 1-1/4" (1.25")
Nuthatch size

Save by purchasing this item in bulk quantity - 50 pieces. 

You can use this metal plate to prevent squirrels from chewing and enlarging the opening on any nestbox with an existing 1-1/4" opening. 

Another handy use for this portal protector is when using an in-box trap when a House Sparrow that has laid claim to a specific nestbox intended for Bluebirds. House Sparrows should not be allowed to breed in Bluebird nesting boxes. Use one of these as a "hole reducer" while the trap is in use to keep Bluebirds from entering the box.  House Sparrows can fit through the 1-1/4 opening, Bluebirds usually can't. Easy installation, four screws provided. Once the House Sparrow has been trapped, remove the portal to let the Bluebird move in.

Strong caution: DO NOT use this hole reducer as a substitute for careful monitoring of the nestbox with the in-box trap! Box traps must be monitored at least hourly to prevent trapping of other native cavity nesting birds. Smaller birds such as Chickadees and Nuthatches may enter the box with a trap, and if left unattended they could die. The hole reducer is merely a deterrent, not a guarantee.