A lot of time and thought goes into building a nest box for owls, but several simple rules must be followed if you want your birdhouse to be used.
The purpose of this article is to give you some guidance and a straightforward technique that will ensure the success of your owl project.
When planning what kind of nest box you’re going to make or buy, remember the adage: “Measure twice and cut once”. To avoid costly mistakes, it pays to have accurate measurements before cutting any wood. Also, remember that these birds only breed once each year and may not use a particular nesting site again until the following spring. So don’t just throw together anything that fits. Instead, make a nest box with the smallest entrance possible but still big enough to keep out predators. This is primarily to avoid raccoons or house cats.
The size of the owl that will use your nest box depends upon what kind of owl you intend for it, so consider which owl species are indigenous to the area where you live and plan accordingly. A good nesting owl needs about 12″ (30cm) by 8″ (20cm). Please don’t make them any narrower than this because they cannot turn around inside. Also, do not allow more than one hole in the front 1/3 portion of the box: even with just one exit, I have seen owls fight over who gets to use which exit first and eventually go hungry when they can’t decide.
My owl boxes are made out of cedar because it is long-lasting and weather resistant. Cedar also has insecticidal properties, which are good protection against woodboring beetles. All owl nest boxes should be faced with screen or hardware cloth to protect them from small predators such as mice, squirrels, raccoons and snakes who may enter through the entrance holes in search of owl eggs or young owls inside the nesting box.
The owl box should be mounted in a tree facing the direction of the prevailing wind, or about 270°, and at about eye level with an owl standing on the ground. About 10 feet (3m) off the ground is a good height for most owl species to nest. The higher you place it up in a tree, the better they will like it.
If you can build your owl box from scratch, try using cedar beams or studs instead of plywood to keep out mice and squirrels who will chew holes in unprotected wood underneath your owl box that may allow predators to enter later when owls are breeding inside. Keep these critters out by applying one coat of exterior latex paint over both sides of the owl box and even inside the holes in your owl house if you can reach them. This won’t hurt your owl but will make it difficult for mice and squirrels to find a home inside the owl nest box.
Owls are highly territorial animals, so it is vital to locate owl boxes at distances of about 100 yards (91m) apart if possible. If that isn’t an option, then wholly avoid owl nests by placing several different owl houses along a route which owls usually fly between their daytime roosting perches in large trees and nighttime hunting grounds over ravines, fields or water bodies where small rodents dwell.
The best location is a tree with an open area of ground underneath so that the owl doesn’t feel trapped or isolated from his hunting grounds. Most owl species prefer a hollow on a down tree trunk but use an owl box instead if you can’t find one.
If you discover that snakes have threatened fledgling owls inside your owl house, try using a cardboard tube in place of one entrance hole until the young birds are big enough to fend for themselves outdoors when they leave their nest at about three months of age.
When designing and building owl boxes, keep these essential things in mind:
1. Don’t use pressure-treated lumber near owl box entrances because it contains toxic chemicals that harm a nesting owl or her eggs.
2. Always use owl nesting boxes made from wood products that are not coated with non-water-resistant paint, stain or preservative of any kind as these will make the owl’s feathers become sticky and thus more problematic for them to fly in wet weather or if they come into contact with water while preening (grooming).
3. Drill small holes about halfway up each side of your owl house so that they can regulate their body temperature by allowing airflow in and out for ventilation purposes. This is important, especially during cold winter months when there is no sunlight to warm the inside of an owl house.
4. It is best to mount cylindrical owl boxes about one or two meters off of the ground and hang round owl nesting boxes from tree limbs about a meter above the ground. That way, any predator who may want to enter into your owl box will have to work much harder for their meal inside. If you don’t have a tall enough tree in your yard, try putting your owl box up on top of a post affixed to a large diameter tree trunk located close by but not directly underneath so as not to create too much shade for baby birds inside.
If you can’t find this kind of neighborhood arrangement where you live, try installing owl houses outside of existing utility poles that are already close to your owl box. The design you choose to install will most likely depend on the location and layout of your yard where you live. This way, owl parents can come and go as they please from their daytime roosting perches in large trees or telephone / electrical utility towers without being seen by passing predators like hawks who use vision instead of hearing vibrations in the air to find a meal.
Some owl species have begun to learn that plastic owl models hung by wires from tree limbs are made by humans and will use them as a place of residence because they offer protection against rain or sun without any effort. But you should install these owl houses with care because some owls have just learned how to fly and may be tempted to land there only if it is raised high enough off the ground so that predators won’t be able to get at them inside.
If you live near a highway, you might want to use an owl house shaped like an owl created by a biologist who specializes in studying owl behavior. The owl shape serves three crucial functions. First, it helps prevent a highway collision with an owl who might fly into the owl house in nighttime darkness and become trapped inside after sunrise. Second, suppose a real owl should land there during the day. In that case, it will be easier for her to see that she has landed on a human owl house replica rather than a real owl nest where her young may be attacked by predators like hawks who use vision instead of hearing vibrations in the air to find a meal.
If you’ve ever created an owl box, tell us in the comments how it went.