How to Protect Nesting Boxes With a DIY Predator Block

By adding a simple predator guard to bird nesting boxes you can stop animals like racoons, snakes, squirrels, and other bird species from raiding the nest.

For free plants see Free Wren Nesting Box Plans and Free Chickadee Nesting Box Plans.

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DIY Predator Guard

If you are providing nesting boxes for birds on your property, it is important to include what are called predator “blocks” or “guards” as well.

A predator block or guard is simply an extra piece of wood mounted to the front of the box. The guard has a hole drilled in its center the same size as the existing nesting box entry. By doubling the depth of the entry hole this way, other animal species find it much more difficult to enter or reach into the box.

It works so long as your nesting box is properly designed with the entry hole right diameter for the specific species nesting there. There is more on this below.

Nesting Box Predators

When I started using nesting boxes for the wrens in our garden, raccoons and other animals soon caught on that they could reach into the box and steal the eggs or hatchlings.

A wildlife camera set up to detect motion at night confirmed my suspicions.

No!

Those nighttime bandits were indeed helping themselves to the contents of the box. Other bird species like starlings were entering the box during the day.

While I try not to interfere unnecessarily in the food web, I felt like I should do more to protect these birds.

That’s when I learned about predator guards. I was skeptical because they are so simple, but they really do help.

You can see how the block stops the bad guys in the video (below).

While it’s unrealistic to think a predator block will stop all possible predators, they really do reduce the number of threats.

Nesting Box Tips

Along with adding a predator block, it is important to choose the right nesting box design for the specific bird species you want to attract.

Every species has different needs for the size and shape of the box as well as the diameter of the entry hole. Even a difference of one-quarter inch matters.

You can read more tips on nesting boxes, recommended entry hole sizes, and why decorative birdhouses are not recommended here.

Once you have the right box, where you mount it also matters. The needs of the species you are hosting will determine the best height, direction (in relation to the sun and wind) as well as the recommended spacing between boxes to respect bird territories.

Using a Nesting Box Predator Guard

Wrens Using Nesting Box

I got this footage using my wildlife camera near the nesting box. Wrens are such fun birds to watch. They mate for life and average between 3 and 7 eggs in each brood, raising up to 3 broods per year.

So cute! And such characters. But a little too attractive to the bigger guys on the food chain.

That’s why I added the predator block around the entrance.

Predator #1

Watch as this starling tries to get in the box. You can see how the baffle block really does make it impossible for him to get inside:

Predator #2

With the motion detection on at night, I happened to get several images and short videos with the automated wildlife camera of a racoon on the fence above the nesting box.

The footage is way too dark to share but upon zooming in and examining it, I could tell the raccoon stood on the nesting box and tried to reach inside several times.

Just by having the predator block, the raccoon could not bend his arm enough to reach inside the box.

Predator #3

Chipmunk! I didn’t get a photo but I actually saw the chipmunk try to climb in the box while the mother bird was inside. The male wren came down from the tree and attacked the chipmunk, literally riding on the chipmunk’s back and pecking him as he fled the scene. Crazy!

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I love it when such simple solutions really work.

~Melissa the Empress of Dirt ♛