Owl nesting boxes are an important aspect of our healthy no-till vineyard. We've built our boxes large enough for Great Horned owls, but ideally suited for Barn owls. Both Great Horned owls and Barn owls are native to our area in California, but their territories don't often overlap. Contrarily, we have seen both Barn Owls and Great Horned owls at the vineyard this year.
Our native owls prey on gophers, voles, and mice making them important employees on the vineyard team. Thus, we must keep them happy and healthy by cleaning out their nesting boxes annually.
The best time to clean out nesting boxes is October-November when the owls aren't typically roosting. This is also the best time to install new owl boxes on your property so that owls have a chance to find nesting sites before the nesting season starts in January-ish.
It is important to check and clean the nesting boxes annually to make sure there aren't any unwanted guests or rotten bedding. For bedding, the Barn Owl Trust and the Lodi Wine Growers both recommend hardwood mulch or bark chips. Avoid using cedar as it can irritate the owls. In this video, we replaced last year's bedding with oak wood chips that we chipped earlier this year from fallen oak limbs. It is recommended to apply bedding 2-3 inches deep to help prevent eggs from rolling, getting cold, or being crushed from incubation. The cleanout doesn't have to be perfect, but avoid using sawdust or straw as these materials can retain moisture and create a moldy mess in your nesting box.
We put the used owl bedding right back into the compost we're making to apply to the vineyard in 2021. It's also important to wash your hands after or wear gloves while cleaning out the owl nesting boxes. Owls prey on mice which can occasionally carry the hantavirus.
In the video, you'll see me dissecting an owl pellet found in one of the boxes. It appears to be the remnants of a mouse, as the skull looks to be a little too small for a gopher. Although we know our nesting boxes were visited this year, it doesn't seem like we've hatched any babies yet. We installed our boxes in June last year, much too late for nesting season. We are certainly ready this year and are hoping for lots of little screeching owlets this season!
This owl nesting box information has been sourced from, Barn Owl Trust, CLAW, Lodi Wine Growers, and The Vineyard Team.