MARK BROWNING

Using Barn Owls for Rodent Control in Florida Orange Groves

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    The Florida Citrus Industry

Florida Oranges

Half a million acres of oranges in FL

With approximately half a million acres of orange groves consisting of over 74 million trees, oranges are the largest cash crop in the state of Florida, creating a 64 billion dollar industry. Florida produces most of the juice oranges in the country, leads the nation in grapefruit production, and is second only to California in overall harvest.

Although Polk County in central Florida continues to produce large orange harvests, most of the citrus farms have been relocated to southern Florida where danger of damaging frosts is far less likely.

Rodent Pests in Orange Groves

As with all crops, oranges are plagued by their own attendant rodent pests. The most damaging species of rodent in orange groves is the roof rat, also known as the black rat and, appropriately, the citrus rat. The roof rat originated in tropical Asia, and immigrated to the United States via ocean going vessels. The warm, moist climates of the southern United States allowed this pest to proliferate and it now is the most prevalent rat in many areas, including Florida.

roof rat 3The roof rat is so called because, unlike its cousin, the Norwegian rat, the roof rat lives mainly above ground, nesting in trees and attics, running from place to place along tree branches, and electric and phone lines. Like most rats, it has a high reproductive rate: females produce five to eight young as many as four times per year and, more devastating for farmers, young females can reproduce at ninety days old.

roof rat eaten orange

Roof rats hollow out citrus

Although they are omnivorous, roof rats prefer fruits and nuts as the mainstay of their diet, and the huge swaths of Florida orange groves harbor high numbers of this pest. Damage to the crops can be high. Roof rat damage to citrus is typified by a quarter to half-dollar sized hole where the rat chewed through the skin and then hollowed out the meat of the fruit. Other damage is done to buildings where roof rats chew through electric lines, water pipes, and create holes in walls, floors, and ceilings.

Vield vole (Microtus agrestis)

Voles damage orange trees by chewing on roots and bark

Orange groves are also plagued by various species of mice which, like roof rats, climb trees, chew on blossoms, new growth, and fruit. And voles, also known as meadow mice, feed on the roots and bark of the trees, weakening trees, and sometimes even killing individual trees by girdling them.

The Barn Owl and Orange Groves

As in California vineyards, damage to orange and citrus groves can be significantly reduced by utilizing barn owls in large numbers to reduce rodent populations. Although this practice has not yet caught on in Florida as it has in California, the results in the western vineyards show that it is a trend that is ready to explode in Florida as farmers in various states and countries report very positive results by using barn owls in integrated pest management programs.

Three barn owls about 4 weeks old

Barn owls have high numbers of young

Barn owls are unique as predators in that they are colonial–willing to live within close proximity to each other. This, combined with their high tolerance of human activity, their prodigious appetites, and high production of young, makes them extremely applicable to natural rodent control programs. A single barn owl family will consume thousands of rodents per year.

The Costs of Trapping Rodents Versus Using Barn Owls

Roof rats are most commonly controlled through trapping. As in trapping pocket gophers in California, it is a labor-intensive, costly method for taking out relatively small numbers of rodent pests. A study in California has shown that when costs are compared between trapping pocket gophers and using barn owls to harvest them, the barn owls are hands down far cheaper: after investing in 25 barn owl nest boxes, one vineyard revealed that over a two year period, the cost of using barn owls to take rodents equaled approximately 25 cents each; this contrasted sharply with their estimate of $8 for each pocket gopher taken by human trapping. Similar costs would apply to trapping roof rats versus allowing barn owls to control them.

Barn Owls in Florida

Florida is an excellent place to use barn owls for rodent control since barn owls are very common throughout the state. Richard Raid, a biologist working for U.S. Sugar, once showed the author a barn that housed ten pairs of owls–all raising young in that single barn. The main limiting factor for barn owls in Florida is the availability of nesting sites. Nest boxes are usually occupied quickly with almost 100% occupancy, making it easy to establish a large and effective population of these rodent-eating owls.

Establishing a Barn Owl Nest Box Program

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The Pole Model made of molded plastic

The beauty of a barn owl nest box program is that it is inexpensive to initiate, and then takes very little maintenance per year to maintain. (Each nest box should be cleaned once per year, a ten minute operation.) And the owl population is self-perpetuating– the owls keep coming back and, importantly, exert a continuous, unrelenting pressure on the rodent population.

Barn owl nest boxes can be erected anywhere the orchard has space to put them: the owls will emerge in the evening and hunt areas where rodents proliferate. Perimeter roads, unused corners of land, and the ends of rows are ideal for erecting boxes and, because barn owls are so colonial, nest boxes can be placed as little as fifty feet apart.

How Many Nest Boxes to Install

Typically, barn owls work best when there are a number of pairs to ensure that the rodent population is kept in check. The basic rule of thumb is one nest box for every ten to twenty acres. Nest boxes can be erected on eight foot poles or posts, enabling easy installation and access. It is best to face them in easterly directions (NE, SE, or E), and to place three to four inches of mulch in the bottom of the box. Other than that, barn owls are highly skilled at spying the entrance holes and soon investigate for potential nesting.

The Florida Orange Grove/Barn Owl Project

We are currently working with several orange grove concerns in Florida to have nest boxes installed in order to demonstrate to citrus growers the potential of using barn owls for natural rodent control in citrus orchards. We will have the nest boxes monitored for barn owl occupancy and breeding success, and we will also have the pellets collected to demonstrate which pest species the barn owls are consuming.

 

 

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MARK BROWNING

Barn Owl Nests

Barn Owl Nesting Sites Around the World

Cavity Nesting Birds

Schenks July 16th.wpd

Barn owl broods are large and need spacious cavities.

Barn owls are cavity nesters, just as are many other birds, such as woodpeckers, titmice, chickadees, wrens, and bluebirds. In fact, the 8500 species of birds in the world can be divided into those that nest in cavities and those that build their own nests. (A few species, such as great horned owls, steal other bird’s nests.)

Originally, cavity nesters primarily nested in hollow trees, in caves, and in crevices in river banks, sandstone cliffs, caves, and lava beds. The advantages to being a cavity nester are many:  there is little work to be done in preparation for egg laying; a snug hollow is dryer and warmer than an open stick nest; wind causes less damage to clutches of eggs and broods of chicks; and cavity nests are more protected from predators.

One disadvantage of being dependent on natural cavities is that the birds have to find one large enough for their brood or they cannot breed successfully. In fact, a lack of suitable nesting sites is often cited as the primary limiting factor in the populations of cavity nesting birds. It is hard enough finding a hollow big enough to raise a brood of bluebirds in; but barn owls must find substantially larger cavities and this can create a challenge for these large owls. The other side of this is that cavity nesting bird numbers can be increased dramatically by providing suitable nesting sites.

Barn Owl Nests in Nature

Barn owls are extremely resourceful creatures; and nowhere is this more evident than in their creative choices when it comes to nesting sites. Naturally, throughout the world, they frequently nest in dead trees that contain suitable hollows. In the states of Washington and Oregon, they nest in the nooks and crannies of volcanic cliffs where the cooling lava created the perfect havens. Sandstone cliffs in the American southwest provide much the same with hollows created by wind and rain. In tropical areas, they sometimes resort to nesting on dead palm fronds. In limestone areas they fly into caves and nest on ledges. And in places where there seem to be no trees or cliffs or caves, such as large grassy marshes, they have been known to abandon all care and nest on the ground.

 

Barn owl in burrow

Barn owls even dig their own burrows in river banks and cliffs.

One of the more interesting habits of barn owls is their digging of their own nesting cavities in the clay and earth of river banks and other places where their claws can work the soil. This was unknown to science until recently when researchers, having found barn owls in such cavities many times, actually observed the animals using their claws and feet to create suitable hollows for their eggs and young.

Barn Owl Nests in Manmade Structures

Structures made by humans opened up a whole new world of choices. When humans first began to build thatch-roofed huts, barn owls found their way into the thatch to raise their young. And when barns began to accompany all human settlements, barn owls expanded and increased wherever humans cleared forest, planted crops, and built barns.

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Barn owls frequently nest in hay stacks.

Barn owls have nested in old machinery, grain hoppers, and barrels left on the ground. In the American southwest they will descend as much as a hundred feet into abandoned mines to raise their young. In Nevada and Washington hayfields where farmers create huge stacks of hay bales, barn owls will nest as little as five feet apart in the hollows between the bales.

In Florida sugar cane fields, barn owls often get into trouble when they try to investigate cisterns as potential nesting sites. It was in sugar cane fields that the author was shown a barn that contained seven nesting pairs of barn owls, all with chicks. One pair nested under a wooden ramp made of slats. Another nested on the floor beneath a child’s plastic swimming pool turned upside down. Two others balanced their nests on wide beams. In old silos of the Shenandoah Valley of Virginia, barn owls dig cavities in the old silage where they lay their eggs.

In other words, barn owls will nest wherever they can!

The Importance of Barn Owl Boxes

Post-Model

The Post Model Barn Owl Box

In parts of the barn owl’s range, a number of changes made by humans have caused barn owl numbers to decline. Dead trees are routinely removed from the landscape. Wooden barns are being replaced by metal barns that do not afford the owls access. And farming has become much more intensive, with few places left that provide good nesting sites for these owls. Yet, in many places, rodent populations proliferate and could support good numbers of barn owls–the main issue is lack of nesting sites.

This is true in almost all types of agriculture, whether it is wheat fields, hay fields, row crops, sugar cane, rice plantations, orchards, or vineyards. In areas of such land use, it is quite possible to attract these owls simply by putting up nest boxes. This can be done in order to create a natural rodent control program on a farm, or for conservation, or merely for the pleasure of having these owls around.

Farmers should take notice of the fact that a single barn owl family consumes between 1000 and 2000 rodents annually and that other methods of killing rodents on a farm, such as trapping and poisons, are far more expensive and time consuming.

For more information, go to our Barn Owl Box Pole Model and Barn Model pages.

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MARK BROWNING

Barn Owls in Missouri

Missouri Barn Owls

Almost the entire state of Missouri has good barn owl populations or the potential for them. Barn_Owl_Flying_8349The barn owl is very common along the eastern edge of the state in the interior river lowlands and the Mississippi Alluvial Plain. The northern half of the state harbors good populations in the Central Irregular Plains region where a lot of crops are grown, and the Ozark grasslands in the southeastern part of the state form excellent habitat for barn owls. The eastern Ozarks, where thick forests dominate, have only localized populations in intermittent areas of grassland; the Corn Belt in the upper northwestern corner has low populations at best.

Missouri Barn Owl Populations by Region and County

The Missouri Department of Natural Resources

Bob Gillespie, biologist for the Missouri Department of Natural Resources, says they get a lot of calls about barn owls, especially during the wheat harvest. He notes that they nest in silos, old barns, hollow trees, and nest boxes in Missouri. They have also been known to nest in some numbers in holes in the banks of the various rivers in the state.

Barn Owl Conservation Programs in Missouri 

During the 1980’s the Raptor Rehabilitation and Propagation Project, Inc. (RRPP) and the Missouri Department of Conservation introduced 57 captive-reared barn-owls into St. Charles County, Missouri. The release area was a 900 acre riverine marsh (Marais Temps Clair Wildlife Area) in the Missouri River basin. A few of these birds, identified by their bands, were found nesting in the same area in subsequent seasons.

The World Bird Sanctuary released over 900 captive bred barn owls into Missouri and Illinois during this time as well. Although breed and release programs have in recent years been less favored than habitat preservation and enhancement through nest box programs, these records show that a moderate amount of success can occur when captive-bred owls are released into good habitat.

 The barn owl was recently removed from the Missouri’s list of threatened species.

Missouri Barn Owl Box Programs

pole-model

As referred to earlier, conservationists tend to favor habitat preservation and installation of nest boxes over breed and release programs to bolster barn owl populations. The most limiting factor for barn owl numbers in otherwise good habitat is the availability of suitable nesting cavities for this large owl. Today biologists are installing nest boxes in prime habitat and the Missouri Department of Conservation encourages residents to put up nest boxes wherever there are grasslands, wheat fields, hay fields, pasture, or wetlands.

Missouri Agriculture and Barn Owls

The wheat fields and apple orchards of Missouri are excellent candidates for using barn BARN_OWL_ORCHARD_550owls in large numbers for rodent control. Voles (meadow “mice”) cause a great deal of destruction in both crops, eating large amounts of grain, and girdling roots and trunks in orchards. The high populations of rodents in both types of agriculture would likely attract barn owls in good numbers in Missouri. Both wheat fields and orchards are known to be good habitat for barn owls in the rest of the country. Any such nest box programs would contribute to conservation efforts on behalf of this beautiful raptor.

For more information, go to our Product Page, read about barn owls and Integrated Pest Management, and our excellent article on the Economic Value of Barn Owls.

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MARK BROWNING

Owl Feathers and Silent Flight

How Owl Feathers Allow Owls to Fly Silently to Catch Prey

The Feathers of Birds

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Down feathers keep birds warm, especially young ones.

Bird feathers, in general, have to be one of the most amazing creations in nature. The flight feathers of wings and tail enable birds to fly—not glide like flying squirrels—but fly powerfully from one end of the globe to the other. Down feathers insulate birds from cold. Contour feathers keep the birds dry in the rain. Powder-down feathers disintegrate into a talcum like dust that birds use to condition the other feathers.

Each feather is a work unto itself: Radiating out from the central shaft that runs up through the middle of the feather, individual vanes also contain barbs that hook over the next vane, and those barbs in turn have barbules that hook on to the barbs. This sophisticated arrangement makes for a very lightweight yet resilient structure. And when these various vanes and hooks become disorganized, a mere pull of a beak through the feather puts them all back together again.

Bluebird On A Stump

Birds use color to attract mates

Beyond these functions, feathers hold the brilliant, defining colors of sexual attraction. Since birds can see colors, various pigments evolve in feathers to make birds, especially the males, more attractive to lure a mate. But not all colors are pigments produced by the feathers. The reds in flamingos come from the foods they eat. And blues cannot be created inside the feathers, so they are created by the structure of the feathers—the soft brilliant blues of jays and buntings and the metallic sheen of purples and greens on grackles and blackbirds are created by infraction—illusory colors that work just the same.

Beyond displaying color to impress the opposite sex, the feathers of doves, pigeons, hummingbirds, manakins, and nighthawks are used in flight to whistle, hum, and boom to create “song” that attracts potential mates.

The Feathers of Owlsbarn-owl-flying

The feathers of owls have other, owlish purposes. These are refinements brought about by darkness and stealth and the quiet of night. As anyone should know who has ever heard a duck or a pheasant take off, feathers in flight create a lot of sound. Songbirds that eat insects and seeds have little need to be stealthy. The same is true for almost all birds.

Even the leading edge of the wing of a hawk through air creates a discernible sound as do the stiff tail feathers cupped to slow down before landing. But hawks use high speed and surprise to capture their prey in full daylight. Owls hunt in the quiet of night where their favorite prey, rodents, utilize their hearing to detect potential predators. Since rodents have poor vision but relatively good hearing, owls rely on being quieter than a whisper to capture their food. This is accomplished by their special feathering.

While the leading edge of a hawk’s wing is sharp and defined (and thus noisy), the leading edge of an owl’s wing contains a serrated, comb-like structure that breaks up the air as it passed over the wing. This soft combing of the air results in almost no sound being produced. In addition, the feathers of the wings, body, and tail of owls are wider and rounder than those of other birds and, to further reduce sound, they are cloaked in a soft, velvety covering of tiny feathers that also soften their passage through air. The result is almost totally silent flight.

Calling Owls in the Wild to Experience their Silent Flight

screech-owl

Red-phase Screech Owl

Try using a tape of owl calls to call in common owl species in your area. You will notice that, if you do not happen to glimpse the owls arriving, the first thing you will hear will be their singing in response to the tape. They will arrive soundlessly, like ghosts. Their prey also never hears their arrival and must rely on their poor eyesight under dim conditions to detect danger from owls.

The combination of silent flight and excellent hearing creates a perfect nighttime predator in owls.

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MARK BROWNING

Barn Owls in Washington

Washington Barn Owls

barn-owl

Barn owls are numerous in most areas of Washington

Barn owls are common in the state of Washington along the entire extension of Puget Sound, along the coast, in the numerous agricultural valleys on both sides of the Cascades, and in the southeastern half of the state. Barn owls are not found to any degree in the Cascades, nor the forested northern mountain counties, but wherever there is agriculture barn owls are found in good numbers. Barn owls even move into large clear cuts where the forest has been cut for lumber.

The river systems, including the Snake and Columbia Rivers, contain good populations that frequently nest in the nearby volcanic cliffs of basalt and lava where vertical cracks and potholes afford excellent nesting sites. In the Palouse Country, where vast quantities of wheat and hay are grown, they are common as well. Here they nest in barns and haystacks. Rehabbers frequently have to bring in nestlings that have been exposed when the hay bales are put on trucks for shipping.

The author once spent a summer harvesting wheat in the Palouse Country. Once the combines passed over the wheat, the farm dogs chowed down on the voles and gophers that were suddenly exposed—and those dogs could barely hold their stomachs off the ground after a day’s eating. This very high number of rodents could support equally surprising numbers of barn owls if enough nest boxes were installed.

Washington Agriculture and Barn Owls

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Orchards attract large numbers of voles, barn owls’ favorite prey.

With almost 40,000 farms comprising 15 million acres, Washington is a major agricultural region. It is first in the nation in growing apples, cherries, pears, and raspberries, and second in the nation in grapes. Orchards and vineyards both attract high numbers of the barn owl’s favorite prey, voles and pocket gophers.

Apple, cherry, and pear orchards are often damaged by voles when these rodents chew on the bark and roots of the trees.

Washington Vineyards and Barn Owls

Washington is second only to California in amounts of grapes harvested. The state grows grapes in all of its agricultural valleys. Many of the regions wine growers use barn owls for natural rodent control and their use is rapidly increasing. Major wine growing regions include the Seattle-Puget Sound Region, Walla Walla Valley, Cascade Valley, Yakima Valley, Pullman-Spokane, Tri-Cities, and the Vancouver-Columbia Gorge. The climates of all of these areas are unique and each produces different qualities in its wines.

Using Barn Owls for Natural Rodent Control in Washington

Nest boxes surrounding Vino Farms

A vineyard surrounded by nest boxes

With the high numbers of barn owls in the state, nest boxes should receive quick and high occupancy. Just as in California, Washington vintners and orchardists can easily attract large numbers of these rodent-eating raptors to their farms, reduce their use of poisons and the labor involved in trapping, and see less damage to their crops, soil, and irrigation systems.

For more information, go to our Product Page, read about barn owls and Integrated Pest Management, and our excellent article on the Economic Value of Barn Owls.

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MARK BROWNING

Texas Barn Owls

The Barn Owl in Texas

Texas Barn Owls

iStock_000020901530MediumBarn owl populations in Texas are excellent and the state is perfect for attracting barn owl families to private properties and establishing nest box programs in agriculture. Barn owls in Texas have been known to nest in trees, cliffs, caves, riverbanks, church steeples, chimneys, barn lofts, hay stacks, deer blinds, and nest boxes.

Barn owls are year-round residents in the state, breeding most commonly February through June, however they have been known to nest in every month of the year. During the winter, they often roost in junipers where they are protected from wind and cold.

They consume voles, pocket gophers, marsh rice rats, cotton rats, Norwegian rats, and mice in such large numbers that they are excellent for significantly reducing numbers of these destructive rodents when attracted to nest boxes.

Distribution of Barn Owls in Texas

Dark blue = excellent populations; Light blue = good to fair; Gray = rare to absent

Dark blue = excellent populations; Light blue = good to fair; Gray = rare to absent

Barn owls are common throughout most of the state except for the forested eastern counties and the high, dry mountains of the Trans Pecos region in the far west. Almost everywhere else this large white-faced, golden-winged owl abounds due to the wide range of agriculture and the prevalence of wild grasslands. As the range map shows, high populations exist in the marsh region along the coast, the sugar cane region of Hidalgo, Cameron, and Willacy Counties in the southern tip of the state, and three major vineyard areas in the panhandle, the north-central edge, and the center of the Edwards plateau.

Texas Agriculture and Barn Owls

Wheat grown across the upper third of the state, sugar cane in the southernmost three counties, rice along the gulf coast, and dairy and cattle farms in the eastern half and panhandle all foster populations of barn owls. Although cotton is not good for barn owl numbers, they are still seen in cotton country.

Texas Wine Country and Barn Owls

Texas has a long history of viticulture, going back to when Spanish missionaries grew BARN_OWL_VINEYARD_842grapes for sacramental wine in the 16th century. Today, Texas is a major grape-growing state, second only to California.

The eight Texas Wine Growing Regions produce a wide array of world class wines. These include the Bell Mountain and Fredericksburg Regions in Gillespie County, the Escondido Region in Pecos County, the Mesilla Valley Region near El Paso, the Texoma Region in the northeast, the Texas Davis Mountains Region in Jeff Davis County, the Texas Hill Country Region located on the Edwards Plateau, and the Texas High Plains Region in the panhandle. All of these regions have unique climates that produce excellent wines.

Using Barn Owls for Natural Rodent Control in Texas

Adult barn owl emerging from nest boxAs in California, Texas vineyards attract large numbers of voles and pocket gophers and these areas have great potential for establishing nest box programs designed for natural rodent control. Quick and high occupancy should be expected in such regions, resulting in less need for trapping and poisoning, both of which are more expensive than using owls. It will not be long before Texas vintners begin to use barn owls to the same degree that California vintners do today. Texas is a perfect state to institute such programs.

But vineyards are not the only places in Texas that harbor dense populations of barn owls. Sugar cane, grown in the three southernmost counties is rife with cotton rats, and barn owls there are always on the lookout for suitable places to nest. The same is true with rice, grown in the moist eastern counties. Large quantities of rice are consumed by marsh rice rats, a favorite prey of barn owls. In areas like these, barn owls cannot find enough nesting sites fast enough and both of these agricultures would benefit immensely from sophisticated barn owl nest box programs. The dairy and cattle farms common throughout the state are also great places for nest boxes, as are the wheat fields of the panhandle.

The Barn Owl Box Company

If you are interested in creating a nest box program in Texas, contact us at the Barn Owl Box Company for any information you might need. We can offer substantial discounts for quantity orders. Look to our Products page for more info on the various nest boxes we manufacture.

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MARK BROWNING

Barn Owl Hearing

The Phenomenal Hearing of the Barn Owl

Owls, being nocturnal hunters, have excellent hearing in general, but barn owl hearing exceeds even that of most owls.

barn-owlOf the 216 species of owls in the world, 200 belong to the Strigidae family. The 16 barn owl species belong to a separate family, Tytonidae. This means that the two groups have different lineages and, therefore, possess different traits. Despite the excellent hearing present in the owls of the Strigidae, barn owls have been shown to possess even more refined hearing than most other owls.

Barn Owl Hunting Behavior

Barn_Owl_Flying_8349Anyone who has ever watched a barn owl hunting in twilight – a pale apparition hovering and quartering across an open field – also will notice how the barn owl keeps its head down, its face pointing studiously toward the ground. That face bears some examination. No other owls possess the pronounced concave facial disk that barn owls possess. This facial disk, created by the feathers to form a hollow disk around the entire face, operates very much like a satellite dish—capturing and locating sound. To either side of the disk sit the two ear openings and these, like other owls, are positioned slightly asymmetrically, another adaptation to allow for greater accuracy in pinpointing the exact location of a sound.

Barn Owl Facial Disk

Three barn owls about 4 weeks old

Young barn owls developing their facial disks

The effect of the facial disk is similar to what happens when you cup your hands toward a sound in order to hear it better. The cupped hands collect sound more efficiently than open air. By turning its face toward the ground, the barn owl collects sounds far more efficiently than your cupped hands. Then the asymmetrical ears send the sounds to the brain with two slightly different signals that allow the barn owls to pinpoint the exact location.

So acute is barn owl hearing that, in a research experiment, barn owls housed in total darkness were able to capture live rodents on a bed of dry leaves with stunning accuracy. Of course, this ability to hunt “blind” is also utilized when barn owls plunge their legs into snow or high grass to capture prey. And since barn owls tend to capture a higher percentage of pregnant female rodents than exist in the population, it is theorized that they may be able to differentiate rodents according to age and sex. This would be accomplished by discerning the difference in sound made by larger, heavier bodies moving through vegetation, or even the difference in the sounds made by different sexes and ages while chewing on grass or seeds.

Pocket gopher foraging at feeder hole

Pocket gopher foraging

In my research project in California where we are measuring the effect of a barn owl population on the rodent population, I frequently see pocket gophers foraging. These rather large rodents are some of the most cautious animals in the world. They use “feeder holes” to forage above ground. In their effort to reach plants to eat, they stretch their bodies out sometimes almost all the way, but never allowing the tip of their tail to leave the feeder hole. This allows them to know exactly where to retreat to from danger, and this they do frequently, whether danger is present or not. The idea of capturing one of these fast moving, cautious creatures by hand seems out of the question, no matter how much stealth could be applied. Yet, I have recorded a male barn owl capturing two pocket gophers in under five minutes on a dark, moonless night and delivering them to his female and chicks.

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MARK BROWNING

California: Land of the Barn Owl

California Barn Owls

While great stretches of the United States, from New York to Iowa, have seen a decline in barn owls since the 1950’s, the state of California maintains surprisingly robust populations of this beautiful white-faced, golden winged owl. In fact, in a state with a wide variety of common raptors, the barn owl may very well be its most common avian predator. iStock_000020901530MediumThough not seen as readily as many hawks due to its nocturnal habits, barn owls nest in large numbers throughout much of the state. They inhabit old barns, outbuildings, silos, bridge girders, holes in cliffs, and even aviation hangars. The author has even seen breeding pairs inhabiting holes in large trees along a busy street in heavily populated downtown Davis. Waitresses in the restaurants there often observe the owls swooping down on rodents that had been attracted to food that humans had dropped earlier in the courtyards and shopping areas that day. This may be the first description of barn owls going to restaurants for their meals! One of the reasons for the abundance of these owls in California is the abundance of wide open spaces in much of the state, much of it natural grasslands. On top of that, much of these grasslands have been converted to irrigated agricultural fields where rodent populations increase significantly, only making the land more agreeable to this voracious rodent predator.

Barn Owls in Vineyards and Orchards

BARN_OWL_VINEYARD_842Recognizing the value of having winged rodent killers on their property, California farmers have led the nation in utilizing barn owls as integral parts to their integrated pest management programs. Growers of grapes, cherries, plums, almonds, and walnuts have been using barn owls for decades now. Literally thousands of nest boxes have been erected in the state and this effort has helped allow barn owls to flourish in the landscape. Their nest box of choice is one that mounts to a metal pole or wooden post. Here is a link for more information on our Barn Owl Box Pole Model.

California Barn Owl Box Programs

The Pole Model Barn Owl Box made by the Barn Owl Box Company of molded plastic

The Pole Model Barn Owl Box made by the Barn Owl Box Company of molded plastic

In California, it is not unusual to put a barn owl box up one day, and find barn owls in it the next. Farmers with large nest box programs typically have eighty to one-hundred percent occupation rates. In a research project designed to determine best methods of creating a nest box program, the author attracted 18 breeding pairs to a single 100 acre vineyard in 2012. These 36 adults fledged 66 healthy young for a total of 102 birds hunting the vineyard by mid-summer. This population on one hundred acres was more barn owls than biologists in Pennsylvania believe exist in the entire state! Such dense populations can take a significant number of rodents and effectively reduce damage to crops and annoyance to farm operations. And the use of barn owls for natural rodent control is growing. Increasingly, farmers are sophisticating their nest box programs by erected larger numbers of nest boxes to ensure that the barn owls can harvest significant numbers of rodents. But farmers are not the only ones interested in having these beautiful owls around: large numbers of property owners are also erecting owl houses around their homes. (Barn owls are aptly named since they do not mind living around human activity.)

Common Rodent Pests in California

Pocket gopher mounds

Pocket gopher mounds

California happens to have dense populations of rodents as well as any California resident will tell you. Mounds, trails, and runs dot the landscape. Different species of rodents dominate different areas, mainly due to moisture and soil types. Two of these species are the most damaging to crops, the pocket gopher and the vole. Whereas vineyards in the Lodi region harbor a majority of pocket gophers, vineyards in Napa and Sonoma are often dominated by voles. Sometimes these two species thrive on the same land.  Both the pocket gopher and vole cause damage to vines, fruit and nut trees, irrigation systems, cover crops, and the integrity of the soil. So the use of barn owls has become a rodent control method of choice for many farmers and property owners.

Barn Owl Distribution in California

The barn owl is common throughout the state except for forested areas and very high elevations which they avoid. The deserts of the southern parts of the state do harbor barn owls, but not in the great numbers that exist in the fertile agricultural regions, wetlands, and grasslands. Even people in the suburbs of large cities like San Francisco, Los Angeles, and San Diego have successfully attracted these large owls.

More Information about Installing Barn Owl Boxes

If you are interested in putting up a barn owl box, make sure you visit our blog post on Best Methods of Installation. For any further questions, email us at info@barnowlbox.com.

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