HOW TO BUILD A SCREECH OWL BOX (Adapted from Audubon

HOW TO BUILD A SCREECH OWL BOX
(Adapted from Audubon Magazine - http://www.audubon.org)
Materials & Tools
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Ruler or tape measure
Pencil
Power saws
Handsaw
Power hand drill with attachments (1/2" bit, 5/8" bit, 5/64" bit for predrilling screw
holes)
3" hole saw
Phillips head screwdriver
Chisel or knife
Hammer
One 1 foot by 8 foot piece of unpainted wood, such as white pine, 1" thick.
(Remember that when you buy a board of this size at the average lumberyard or
home store, the 1 foot width will really be about 11 ¼" and the 1” thickness will
really be about ¾".) After you cut the box pieces, you'll have leftover scrap wood
to make the 1” x 2” x 4” perching ledge for inside the box (see Step #11 below).
(24) 2" deck screws, coated or galvanized to prevent rusting
Two 1 ½" screws (to attach the perch)
Two 1 ½" brass hinges, with screws
One 1 ½" minimum length eye bolt
The Hungry Owl Project is a program of WildCare (www.wildcarebayarea.org), a 501(c)(3)
nonprofit organization, tax ID #51-0172331. WildCare offers practical, respectful and humane
solutions in a complete cycle of programs that illuminate the inherent value of wildlife and the
importance of a diverse and healthy eco-system. These programs include a wildlife advice
hotline, veterinary hospital for wild animals, wildlife solutions services for property owners
and education programs for children and adults.
website www.hungryowl.org email info@hungryowl.org
179 The Alameda, San Anselmo, CA 94960 415.454.4587
Construction
(1) Start by remembering this old adage: Measure twice, cut once. After you've made
your measurements, cut the piece for the back (20 ½" x 7 ¾"). Next cut the piece for
the bottom (8 ½" x 7 ¾"), then the piece for the front (16 ½" x 7 ¾").
(2) Cut the sides. First cut a piece that is 10" x 35 ½". Before you make the next cut,
make sure you've measured 17" up one side of the board and 18 ½" up the other side,
and that your cut line connects these two points. You should end up with identical
pieces, 18 ½" in the back, 17" in the front and 10" from front to back.
(3) Finally, cut the top piece (13" x 11 ¼" -- the full width of the board).
(4) Drill three 5/8" ventilation holes about 1" below the top of each side. Drill five ½"
drainage holes in the bottom (one in the center, one near each corner).
(5) With the hole saw and a keyhole saw or jigsaw, make a 3" wide by 4" high, eggshaped entrance hole. The center of the hole should be 4" below the top of the front
piece. The hole should be centered between the sides. We recommend the ‘egg
shape’ because the owls like to sit in the opening and an oval shape will facilitate that.
If, however, the complex cut is too difficult to make, drilling a simple 3” diameter round
hole will suffice.
(6) With the chisel or knife, make deep horizontal scratches on the inside of the front
piece, from the bottom up to the entrance hole (for the young owls to climb out).
Before moving on to the assembly steps below, sand all the edges and corners of the
cut pieces as well as around the entry hole to remove splinters and sharp edges.
(7) The side pieces should overlap the back piece with the top of the longer edge of the
side pieces aligned with the top edge of the back. This should leave about 2” of the
back extending below the bottom of the side pieces. Screw the side pieces into the
edges of the back piece; use three screws for each side. The top of the side pieces
should slope toward the front. (Pre-drill all the holes with the 5/64" bit.)
(8) Screw the bottom of the box in place, setting it about 1/2" above the bottom edges
of the side pieces. Use three screws to attach the bottom to each side and to the back.
(9) Screw the front piece in place, insetting it between the side pieces such that it is
snug against the front edge of the bottom piece. The bottom of the front piece should
align with the bottom of the side pieces. This will leave a 1/2” ventilation gap between
the top of the front piece and the underside of the top piece. Use three screws to attach
the front to each side and to the bottom.
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(10) Using the two hinges, attach the underside of the top to the front piece. Install the
eye bolt through the top piece and into the edge of the back piece; this will hold the top
in place but enable you to open the box to clean out the inside.
(11) Install the perching ledge (1" x 2" strip of wood 4" long) inside the box to the front
panel, 3" under the hole opening.
Make sure there are no nail points sticking out anywhere inside or outside of the box. If
any are present, file them down flush with the wood.
Stain the OUTSIDE of the box using an environmentally friendly product, such as waterbased deck stain. This will extend the life of the box.
Hanging the Box
The most important thing to remember when hanging the box: Be careful! Ten feet (or
higher) is a long way off the ground, especially if you're carrying an owl box.
Lag screws in pre-drilled holes can be driven through the back of the box (including
ones through the portion of the back piece which extends beyond the bottom of the
box). If, however, you don't want to nail or screw the box to the tree, you can attach a
cable or light chain to the box through holes drilled in the back (both top and bottom).
The cable or chain should be just loose enough to be worked up over the trunk's
irregularities. You might need to tighten the cable or chain when the box is where you
want it.
To have the box professionally installed for a fee, contact Jim Cairnes, Small World
Tree Service at 415-455-0909. Zach Wilder of Sonoma Marin Arborists may be able to
install your box free. You can reach him at 415-455-8733 or
smarborists@sbcglobal.net.
It's important to place the box correctly. The natural cavities that screech owls choose
are typically 12 to 20 feet above the ground and in deep shade. As the female incubates
the eggs, the male is apt to spend the day roosting in dense foliage within about 20 feet
of the nest. After you've placed an inch or so of dried leaves in the bottom of the nest,
hang it at least 10 feet up on the trunk of a large tree. Try to place it away from
sidewalks or doors, since the owls vigorously defend their nests against perceived
threats. In fact, when the young are near fledging, some unusually spunky adults
may swoop down at people or pets who wander too close, even raking them with their
talons. It seems that placing the box in as secluded a spot as possible will benefit both
the owls and everyone else who might be around them.
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A Little Night Magic
Want to improve the after-hours scene in your neighborhood? Try hanging a screech owl box.
By Kenn Kaufman
Reprinted from National Audubon Magazine
Night creatures go largely unseen, so people are often surprised to learn that they might have owls as neighbors.
But it's true. Take screech owls, for example. Over much of this continent, from southern Canada south into
Mexico, they can be common; in fact, studies have shown that screech owls can thrive in small towns, suburbs,
even city parks.
Still, in America's tidy neighborhoods, as homeowners and townships trim away dead trees and large limbs and fill
in natural cavities, good screech-owl nesting sites can be hard to find. Human-made nest boxes can make up for
any shortage of natural nesting cavities, enabling these petite owls to live in places where they might otherwise be
absent. This can help stabilize their populations.
There are two widespread species of screech owls, eastern and western, differing most obviously in voice. Neither
actually screeches, except when agitated; most of their calls consist of mellow whistles and trills. Screech owls
may spend their days sleeping in dense foliage or sitting next to tree trunks (where their mottled pattern provides
camouflage), but more often they will be inside a cavity of some sort--a hollow limb, for instance, or a large
woodpecker hole--hidden away from the sharp eyes of small songbirds, which will fuss about in a most irritating
way when they find an owl sitting on its day roost. While a good cavity can help the owl avoid the annoying
attentions of songbirds, it becomes essential during the nesting season.
Screech owl boxes have not inspired as much design experimentation as those for bluebirds or purple martins, but
we do have some idea of what works. Fred Gehlbach of Baylor University, the world's leading authority on screech
owl behavior, tried some variations on nest boxes as part of his studies on nesting habits. Gehlbach started by
measuring natural cavities favored by the owls. He found the birds tended to use deeper cavities, more than 10
inches deep, with entrance holes not much larger than the minimum needed for their own entry. He also found that
while the owls would use cavities with floors only six inches across, young owls were apt to fledge too early from
such crowded nests. He had better success using boxes with floors that were eight inches square.
Although many experts recommend cleaning out nest boxes yearly, preferably in early spring, there's some
disagreement on this point when it comes to screech owls. One reason for this is that the debris you'll find in
screech owl boxes may have a life of its own.
Perhaps the oddest part of screech owls' behavior is their association with blind snakes, which have been found in
the owls' nests. These odd snakes, which resemble large earthworms, normally appear only at night. Gehlbach and
others have observed that the owls bring these small snakes to their nests and release them. The snakes feed on the
larval and pupal stages of ants and flies that live in the nest debris, reducing the number of insects competing for
the headless mice, dead beetles, and other tidbits cached by the owls. Gehlbach's studies suggest that the snakes
actually contribute to the owls' breeding success.
PLACEMENT
It's important to place the box correctly. The natural cavities that screech owls choose are typically 12 to 20 feet
above the ground and in deep shade. As the female incubates the eggs, the male is apt to spend the day roosting in
dense foliage within about 20 feet of the nest. After you've placed an inch or so of dried leaves in the bottom of the
nest, hang it at least 10 feet up on the trunk of a large tree. Try to place it away from sidewalks or doors, since the
owls vigorously defend their nests against perceived threats. In fact, when the young are near fledging, some
unusually spunky adults may swoop down at people or pets who wander too close, even raking them with their
claws. So while placing the box in as secluded a spot as possible is good for the owls, it might be better for us, too.
Kenn Kaufman is the author of Birds of North America (Houghton Mifflin).
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Habits and Habitat of Western Screech Owls
From www.owlpages.com
Hunting & Food: Hunts mainly in open woodlands, along the edges of open fields or wetlands, or makes short
forays into open fields, searching for prey mainly while in flight, rather than from a perch. When prey is located,
the owl dives quickly and seizes it in its talons. They also capture flying insects on the wing. Small prey is usually
swallowed whole on the spot, while larger prey is carried in the bill to a perch and then torn apart.
An extremely wide range of prey species is captured. The most favoured prey are small microtine rodents and deer
mice, larger insects, or small birds depending on abundance. Prey species include shrews, orthopterons, insects
(including beetles, larval moths & butterflies), birds, pocket gophers, voles, salamanders, kangaroo rats, wood rats,
pocket mice, bats, grasshopper mice, gophers, frogs, locusts, and scorpions, crayfish, worms, snails, small fish.
Nests are almost always in deciduous trees such as oaks, cottonwoods, maples, sycamores and large willows, but
also in large cacti, Douglas-fir snags, and junipers. Western Screech Owls are dependent on deciduous woodlands
or open mixed forests that have suitable nesting sites and sufficient prey densities. Removal of riparian forest in
drier regions will cause population declines because most densities are highest in riparian zones. However, this
adaptable owl can survive in wooded suburban areas and city parks as long as long as they are not directly
persecuted. Populations likely fluctuate more depending on prey availability. Nest box programs can enhance local
populations, especially in areas short of suitable tree cavities. Landscaping practices that include removal of dead
and dying trees can eliminate this bird as a breeding species from local areas.
Habitat: Western Screech Owls inhabit a wide variety of habitats. On the northwest coast, they inhabit humid
Douglas-fir, western hemlock, western red cedar, and Sitka spruce forests along the edges of clearings, rivers, and
lakes. Further inland they occupy a narrow ecological niche of lowland deciduous forests, especially riparian
woodlands along river bottoms. Southern populations inhabit lowland riparian forests, oak-filled arroyos, desert
saguaro and cardon cacti stands, Joshua tree and mesquite groves, and open pine and pinyon-juniper forests. They
avoid dense forests because Great Horned Owls use that habitat, and high elevation forests. In general, they require
open forests, with an abundance of small mammals and insect prey, and cavities for nesting. They roost mainly in
natural or woodpecker cavities in large trees, but also in dense foliage of deciduous trees, usually on a branch next
to the trunk, or in dense conifers.
Responsibilities of Having an Owl Box
Thank you for your interest in owl boxes. Barn Owls and Western Screech Owls will use artificial cavities in the form of nest boxes.
The decision to put up an owl box should not be made lightly. There are responsibilities involved. These include:
• A strong commitment not to disturb nesting owls. All native birds are protected by Federal Law, especially when nesting.
Any disturbance is a Federal offense. So, if you decide that your tree needs cutting down, or trimming, and there are owls
using your box, you will have to wait until the fall to make any changes to the tree.
• If the box is located in Marin County, notifying the Hungry Owl Project if you decide to move. Depending on time of year, it
may not be acceptable to move the box! Western Screech Owls will return to the some box over multiple seasons, so it is
best not to move the box at all.
• Contacting a licensed wildlife hospital, the Hungry Owl Project, or your local humane society if you find an injured or
orphaned owl.
• If you feel comfortable with these responsibilities, and have the right habitat for Western screech owls, we encourage you to
install an owl box to help provide homes and protection for these beautiful, and beneficial, predators.
If you have any questions, please contact the Hungry Owl Project at 415-454-4587. Please visit our website: www.hungryowl.org
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