Large natural nesting cavities are in short supply, making each big nest box valuable to birds like this Eastern Screech Owl, photographed by Michael Sparks. Pairs of Wood Ducks will soon be investigating big nest boxes provided by dedicated birders.

Is this the year for you to add a Big Nest Box to your property? Or to lead the charge for adding one to a nearby nature center or refuge? Big nest boxes provide another level of satisfaction as you try to attract the set of larger birds that nest in larger cavities, ranging from colorful Wood Ducks to miniature Elf Owls or big Barn Owls. Providing big nest boxes is a true conservation effort as you help cavity nesting birds during the most important part of their life cycle, by ensuring there are plenty of safe nesting sites available each spring.

Consider making this the year you add a big nest box to your local environment; and if you don’t have the right habitat, or a larger property, you may want to work with staff at a city park, local nature center, wildlife refuge, or an area property owner on a cooperative project. You can also ask for help from a local public or private group to install a big nest box. Often, naturalists and property managers welcome such requests, and you never know how enthused the people you contact might become. They may be inspired by your initial interest, and if they enjoy the process, one nest box may lead to more in the future.

Regardles of whether you decide to build or buy a big nest box, it should have a hinged side panel so you can access the inside of the big nest box – to periodically monitor nesting status, and to clean and maintain the unit at the beginning and end of each nesting cycle. Installing a big nest box can be a bit much for one person to do, so it may require a group of helpers at the installation point of the project. You can even ask a favor of the local power company or a construction company that might help install a nest box using one of their specialized bucket trucks.

When you begin considering installing a big nest box, the first step is to make sure the species you are interested in attracting nests in your area. Check the range map for species you’re interested in, then determine what it will take to build or buy an appropriately sized nest box and install it.

Whoo is a Big Cavity Nesting Bird? – Not all birds nest in bird houses; but here is a comprehensive list of the larger cavity nesting birds found in the United States and Canada: Owls – Western and Eastern Screech Owls, Northern Saw-whet Owls, Boreal Owls, Northern Pygmy Owls, Ferruginous Pygmy Owls, Elf Owls, Barn Owls, and Barred Owls; Falcons – American Kestrels; Ducks – Wood Ducks, Hooded Mergansers, Barrow’s and Common Goldeneyes, Common Mergansers, and Buffleheads.

3 Standard Big Nest Boxes – As for the appropriately sized aspect to your big nest box planning, let’s start with a baseline size for a big nest box. Nest Box A is an appropriate size for Eastern Screech Owls, Western Screech Owls, Northern Saw-whet Owls, Boreal Owls, and American Kestrels. Nest Box A has an entrance hole 3 to 4 inches in diameter, so maybe emphasize the larger diameter to include all potential cavity nesting birds. The overall structure should measure about 17 inches high with 9½ inch sides and 11 inch front and back panels.

While some cavity nesting ducks might use Nest Box A, nest boxes made exclusively for Wood Ducks and similar-sized cavity nesting ducks tend to be larger in size overall, which brings us to Nest Box B here, which is an optimum size for Wood Ducks, Hooded Mergansers, and Common Goldeneyes. Ideally, the entrance hole is a horizontal oval that measures 3 inches high by 4 inches wide. The overall size is larger, measuring 24 inches high x 8 sides x 9 inch front and back panels.

A third size will accommodate the smaller group of cavity nesting owls – Northern Pygmy Owls, Ferruginous Pygmy Owls, and Elf Owls. Nest Box C has an entrance hole that measures 2 inches in diameter with an overall size of 13 inches high x 7 inch sides x 7 inch front and back panels. If you would like to provide a big nest box for Flammulated Owls, you can easily modify the above plan to include a 2½ inch diameter entrance hole – a little larger for the “flame owls,” but for the other owls, the smaller entrance hole keeps some competitors from using the nest box.

And now for the 2 Really Big Owl Nest Boxes for Barn Owls and Barred Owls. Barn Owl nest boxes have gained a lot of popularity in agricultural areas, where landowners want to attract these excellent natural rodent controllers to their fields and vineyards. Barn Owl nest boxes have an oval entrance hole measuring 3¾ high x 4½ wide, positioned at one side of the long structure, which measures a whopping 16 inches high with 12½ sides, with front and back panels measure 23 inches long. Barred Owl nest boxes have the largest entrance hole, measuring 7 inches in diameter, with the structure measuring 23 inches high with four 13 inch wide sides.

Location, Installation, & More

These are some basic size considerations when considering what birds you would like to benefit by providing a big nest box, but there are a number of other important elements to installing and positioning the nest box in the right habitat, at optimum height, and other helpful tips like: Add 3 inches of wood shavings to the floor of a big nest box (owls, kestrels, and even ducks don’t build up nesting material, so it’s helpful to provide a soft bedding to keep nestlings above the floor of the nest box.)

As for learning more about the varied nest box elevations and habitats for different species, we send you to the NestWatch website, provided by the Cornell Lab of Ornithology at NestWatch | All About Birdhouses - NestWatch That’s also where you can get complete nest box plans for how to build a big nest box for the birds you choose to attract, all for Free.

If you’re not interested in a do-it-yourself project, you can always purchase a Kestrel Nest Box or Screech Owl Nest Box at Owl & Kestrel Houses at BestNest! and for a Wood Duck Nest Box, the best source is BestNest at Duck Houses at BestNest.com!

One more thing to keep in mind is that birds may not occupy a nest box immediately. It may take a season or longer for birds to find and utilize your nest box; but be patient, keep up the good work, and appreciate that having an extra cavity site or 2 in your area is much better than not having enough. Eventually, you will be rewarded with years of exciting nesting activities.

It’s all well worth the effort when a screech owl or Wood Duck picks your big nest box to nest in. Nothing can be more rewarding for birders, and nothing can benefit cavity nesting birds more than ensuring they have plenty of safe nesting sites available each spring. The timing is right to get a new big nest box into position before owls, kestrels, and ducks begin migrating north to search for this spring’s nesting cavity.

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