Barred Owl Nesting Box

Earlier this year SCA members expressed a keen interest in building a barred owl nesting box. It’s time to get building!

Barred Owl

Barred owls look for an existing cavity in mature trees with the cavity 20 to 40’ off the ground. Ideal cavities are 10-13” wide and 14 -21” deep. There aren’t many naturally occurring cavities that size so your owl box has a good chance of attracting a nesting pair. The owls will often prospect a nesting site a year before they nest, so don’t be discouraged if it’s not occupied right away. One to five eggs are laid with an incubation period of 28-33 days. Expect the nestlings to take up to 35 days to fledge.

The drawings suggest using a 4’x4’ piece of ¾” thick plywood. If you’re going to use plywood find someone else who is building a box so you can split a full sheet of plywood and other supplies. If you have old wood you want to repurpose by all means do. If your sizing isn’t exactly as specified in the drawings don’t worry. A natural cavity in a tree won’t be precisely sized either. The entry hole into the box is probably the most critical size to match. The material has to be thick enough to screw together so ¾” is probably the minimum thickness. Ensuring your cuts are square will make assembly easier and help make the box weatherproof. At the end of the day you want a nesting box that can withstand the winds and weather of the bay.

The drawings for boxes are incredibly detailed with lots of good photos and construction tips. Study them well. We will try and make a PDF available on our website should you want to print or download the drawings. I’ve built and mounted a couple of nesting boxes so please contact me (Peter Adams – ) with any questions.


The boxes need to be at least 20’ off the ground. That takes a serious ladder leaning against a round tree and that sets off a lot of alarm bells. Hauling the box up the tree and then fastening it to the tree from the top of the ladder sets off more alarm bells. Take this very seriously and consider hiring a contractor to help. By following the procedure outlined in the building instructions you can reduce the chances of an incident.