Kristi,
The entry on the nestbox shown in your photo is too low – dangerously so. A completed nest in this box is going to be nearly level with the bottom of the entry hole, allowing any predator to easily reach anything in the nest. Another problem with this low entry location is that it’s more vulnerable to windswept rain than an entry placed up high, nearer the roof. I would make another door with the entry near the top of the box, or replace this box altogether.
As Gin pointed out, wire guards such as the Noel guard don’t work for avian predators. Those guards are primarily to stop cats and raccoons.
Fred
Waleska, GA
NestboxBuilder