Living Center Oregon

Sustainable Living Center Oregon

Truffle Owls

Truffle Owls ……

Voles, squirrels, chipmunks and gophers love truffles just as much as humans do.  If we want to cultivate Truffles we must control these critters.

spotted-owlBring on the Owls!!

Using owls to control gophers is an option. Installing owl boxes will encourage owls to make their home where we want them. While owls prey on gophers, their habit is to range far from their nesting boxes, so using them as your main gopher control is somewhat unreliable. When a single gopher is damaging an entire farm or crop quickly, quick fixes like trapping or baiting are necessary.

The Western Red-Backed Voles loves Truffles

The western red-backed vole is found in northern California and western Oregon in the United States. The northern limit is defined by the Columbia River, with the range extending south to around 62 mi north of the San Francisco Bay. The range extends from the summits of the Cascade Range in the east, to the Pacific Ocean. They live mainly in Douglas Fir forest.

They live largely underground in an extensive system of burrows. It feeds primarily on fruiting bodies of hypogeous fungi. These mycorrhizal fungi (triffles) are the symbionts of the Douglas Fir trees around it. Rhizopogon vinicolor is one such which is associated with the Douglas-fir. Fruiting of the truffles takes place in well decayed timber when the nutrients are becoming exhausted.

Because the truffles are underground, their spores are not liberated into the air as in most fungal species. However, the spores are found in the vole’s droppings and are deposited throughout its burrows, thus enabling the truffle to spread and form associations with uninfected trees. It has been found that in a clear-cut forest where all the dead wood and trimmings are removed, the mycorrhiza stops fruiting, the vole population dies out and newly planted trees fail to thrive.

This is an example of a three-way symbiosis. The vole gains food from the truffle and spreads its spores. The truffle gains photosynthetic products from the tree which benefits from the nutrients produced by the truffle.

The western red-backed vole, as a denizen of old-growth forests, it plays an important role as prey to a number of species. For the northern spotted owl, western red-backed voles are one of the top five prey species. The red tree vole, northern flying squirrel, and western red-backed vole constitute more than 75% of the spotted owls diet.

To Control Voles we use Owls

Owls are permanent residents and may nest at any season. Their clutch of five to ten white eggs will produce a varying number of the young, depending on availability of prey. Incubation requires three weeks. The young, which vary in size due to their hatching dates, fly at about seven weeks of age. Barn owls often nest in the same site repeatedly.

barnBarn owls are considered to be our most beneficial owl, owing to their appetite for animal pests. One once was observed delivering 16 mice, three gophers, a rat and a squirrel to a nest within 25 minutes. Common barn owls are threatened by the loss of prey habitat. The barn owl’s primary prey are voles and to a lesser extent mice. The barn owl is found worldwide, nesting almost totally in buildings in the Old World and in hollow trees and burrows in much of the western United States.

Barn owls have become very popular to attract for various reasons. Owners of truffle orchards, and farms have found that barn owls can significant reduce damage by crop-eating rodents. Property owners can benefit the same way with sometimes no more than one or two nest boxes. Conservationists are finding that erecting owl houses is the best way for bringing back numbers of barn owls in areas where they have declined. And bird lovers simply love having them around to enjoy the opportunity of watching these white-faced, golden winged raptors sail out over a field at dusk on the hunt.

The popularity of attracting barn owls has resulted in a wide range of barn owls box designs, both do-it-yourself and those that are marketed commercially. Often, these designs do not take into account the biology and daily needs of these large owls. With so many versions of nest box to choose from, some excellent, some not so good, this article is intended to help barn owl enthusiasts make wise decisions about which elements are ideal for successfully attracting and housing these beautiful raptors.

The Five Most Important Design Elements for a Barn Owl Box

pkasticThis barn owl box is shallow but long

  1. Appropriate Size: Too many barn owl box designs create a nest box that might be only 18” deep. While this size can attract a breeding pair, keep in mind that barn owls produce an extraordinary number of young—seven is quite common. And keep in mind that the entire brood of owls must reach adult size inside that nest box before fledging, each of them 12 to 14 inches high, and flapping their wings in preparation for flight. In such small boxes, flight feathers are damaged, smaller birds are not found to receive food, and young birds are pushed accidentally from their nest boxes. In short, fewer birds survive from such owl houses. Rule of thumb: select designs that are at least 24” deep, 14” high, and 14” wide.
  1. Size of Entrance Hole: Many designs err on the size of the entrance hole, usually making them too large. All cavity nesting birds, including barn owls, prefer an entrance hole that is just large enough for them to squeeze through, but too small for larger animals that might prey on the eggs or chicks. Numerous designs dictate a six or seven inch hole. This is far too large and may cause barn owls to shun such a nest box. Other designs call for a hole as small as 4 ½” inches. Although some barn owls can fit through, barn owls vary in size, with females being larger than males and American barn owls larger than those in Europe. Choose a design with a 5” to 5 ½” entrance hole.

 Location of Entrance Hole:  A number of designs call for an entrance hole that is almost level with the floor. This is a poor choice because the ever curious and rambunctious young tend to crowd toward the entrance hole as they get older. This design allows for them to fall out way too early. Always pick a design with the entrance hole at least six inches off the floor.

 Wooden boxes should be painted white to keep them cool and repainted every year or two

  1. Color: Many wooden boxes are left natural to blend into the environment. While this may satisfy certain aesthetics, the problem is that most wooden boxes are heat traps especially in western and southern states. As the sun beats down on dark wood, the interior can become excessively hot. Biologists have found young owls, too young to leave the nest, on the ground where they took refuge from the stifling heat inside wooden boxes. If you do buy or make a wooden box, be sure to paint the entire outside with bright white paint to reduce heat absorption and plan to repaint every year or two.

 Material: Most commercially made boxes and available plans use half-inch plywood.

Plywood boxes tend to deteriorate over time

The problem with such plywood is that, after the expense and labor of construction and installation, half inch plywood deteriorates rapidly in sun and rain. The alternate choice, ¾ to 1” plywood will last somewhat longer. The problem with thicker ply is that it creates a box that is very heavy and difficult to install. Our solution is to use a plastic 15-gallon barrel with a removal opening on the back.

 If the barrel is to be placed in an exposed situation. Approximately nine drain holes, 1/4 to 1/2 inch in diameter, should be spaced throughout the bottom. Cover the bottom with 1 or 2 inches of wood shavings, as barn owls do not collect nest material.

How to Attract Owls

There are more than 200 species of owls in the world, but only a few are comfortable enough to become backyard species. The most common backyard owls include:

  • barnBarn owl
  • Barred owl
  • Eastern screech owl
  • Great horned owl
  • Western screech owl
  • Northern Spotted owl

The Great Horned Owl is the most commonly encountered owl in Oregon. It is a large, stocky, powerful owl with large yellow eyes and distinctive feather tufts or “ears” above the eyes. Plumage color varies from dark brown in western Oregon to pale grayish brown in southeastern Oregon. The throat is white.

It is a fairly common permanent resident throughout the state, but generally absent in areas above the timberline.

Depending on the local habitat, regional owl ranges and how attractive the yard is for these birds of prey, other owls may also become backyard visitors.

 great_horned_owl3Shelter: Owls need somewhat dense, ature trees with good trunks to roost during the day, preferably in a shaded, secluded area. Both coniferous and deciduous trees are suitable if they are a good size. Empty owl nest boxes are also good alternatives to natural shelter, but providing natural spaces where the owls can feel safe during the day is the best way to encourage them to roost nearby.

As with attracting any birds, the key to attracting owls is to provide their four basic needs: food, water, shelter and nesting sites.

easternscreechowlFood: Owls will not visit bird feeders, but it is possible to provide a steady food source for these hunters. Because owls eat mice, voles, gophers and similar small rodents, backyard birders who have mice nearby are more likely to attract owls. Leaving grass uncut, adding a brush pile and leaving seed on the ground will make the yard more mouse-friendly, which in turn makes the habitat more owl-friendly. Avoid using poisons or traps to eliminate mice or other prey, and let owls take care of the problem instead.

 western-screech-owl-montanaWater: Owls get the vast majority of the fluid they need in their diets from the prey they consume, and they are not frequent visitors to bird baths. In hotter climates and during the summer, however, owls may visit slightly larger, deeper bird baths to drink or bathe. Providing this type of water source in a secluded area is more likely to encourage owls to visit.

 great_horned_owl3Shelter: Owls need somewhat dense, ature trees with good trunks to roost during the day, preferably in a shaded, secluded area. Both coniferous and deciduous trees are suitable if they are a good size. Empty owl nest boxes are also good alternatives to natural shelter, but providing natural spaces where the owls can feel safe during the day is the best way to encourage them to roost nearby.

 Nesting Sites: Hollow trees are most owls’ preferred nesting sites. Smaller owl species that are more likely to be common in backyard may also use large nest boxes that are positioned 10-20 feet above the ground on a large tree. Barn owls may also use abandoned buildings for nesting, and leaving a barn or shed open for the birds to access can give them a great place to raise a brood. Nest boxes should be put up in January or February for owls, since these birds nest much earlier than other backyard species. The boxes should be monitored to be kept free from wasps, squirrels, rodents, raccoons or other birds or guests that may discourage nesting owls.

If your yard is owl-friendly but you still have trouble attracting these nighttime raptors, there are additional steps that can help make the yard even more appealing.

Leave large, bare branches and dead trees intact as much as possible to provide perches for hunting owls.

 Create a rustic, natural section of backyard habitat with little pruning or maintenance where owls can feel more comfortable, especially for nesting or roosting.

 Avoid extensive exterior lighting such as illuminated water features, flood lights or spotlights, even with motion sensors. Owls hut more effectively in darkness and will not visit well-lit yards.

 Keep pets indoors after twilight and during nighttime hours. This will keep the pets safe from hunting owls and keep pets from scaring away the mice and other rodents that the owls will hunt.

Take steps to prevent bird window collisions on large windows that might be a danger to hunting owls.

While these tips can help you attract owls, it is just as important to avoid some behaviors that can harm these birds.

Do not release cage mice or other small pets with the intention of providing supplemental food for owls, and do not buy dead mice or offer other meat to tempt owls. These types of pets will not survive outdoors, and owls must hunt live prey to meet their nutritional and behavioral needs.

Avoid frequent use of recorded owl calls that can agitate the birds and distract them from the hunting or nesting activities they need to survive. Too many calls may also simulate excess predators in the area, which can deter other birds from visiting.



Barrel Owl Box should be installed high to lessen human disturbance and the dangers of predation from snakes, raccoons and cats. If placed in a barn, the front should face into the barn. The back can be nailed flat to the barn. Usually, a brace or stud can be located on which to secure the box firmly along one side. Metal straps attached on the back can be bent to hang the box in a barn or inside a silo. In some regions, barn owls use boxes that are simply wired in place high in a large tree.

The most productive site for a barn owl box is where individuals have been seen. Due to the species’ rarity, the possibility of attracting them in other areas is remote but worth a try. The best localities are rural. Areas where there are open grasslands and crop fields and where grain spillage results in high mouse populations are especially suitable for nesting barn owls.

Place nest cones in trees in the fall so they can be located by owls by the following January.

  • Place the nest in a live hardwood tree that is at least 12″ in diameter.
  • Placing nest cones in orchards or on farm woodlots can help control rodent populations.

Oregon Coast Truffles Company

  • 541-996-3671
  • 82 Siletz Highway
  • Lincoln City, OR






This entry was posted on February 18, 2017 by .