Posts Tagged: owls
UC Davis Biodiversity Museum Day: See 'Bird's Eye View' at the Raptor Center
Last year during the 12th annual UC Davis Biodiversity Museum Day, visitors to the California...
This is the newly installed mural, "Bird's Eye View," which visitors to the California Raptor Center, UC Davis campus, can see during the UC Davis Biodiversity Museum Day on Saturday, Feb. 10. (Photo by Diane Ullman, UC Davis distinguished professor of entomology and artist)
Owls Contribute to an Integrated Pest Management Program
Integrated Pest Management (IPM) is a science-based pest management process which focuses on...
Is wildfire management ‘for the birds’?
Spotted owl populations are in decline all along the West Coast, and as climate change increases the risk of large and destructive wildfires in the region, these iconic animals face the real threat of losing even more of their forest habitat.
Rather than attempting to preserve the owl's remaining habitat exactly as is, wildfire management — through prescribed burning and restoration thinning — could help save the species, argues a new paper by fire ecologists and wildlife biologists and appearing today (July 2 ) in the journal, Frontiers in Ecology and the Environment.
The paper compares the plight of the owl with that of another iconic threatened species, the red-cockaded woodpecker, which has made significant comebacks in recent years — thanks, in part, to active forest management in the southern pine forests that the woodpecker calls home. Though the habitat needs of the two birds are different, both occupy forests that once harbored frequent blazes before fire suppression became the norm.
“In the South, the Endangered Species Act has been used as a vehicle to empower forest restoration through prescribed burning and restoration thinning, and the outcome for the red-cockaded woodpecker has been positive and enduring,” said Scott Stephens, a professor of environmental science, policy and management at the University of California, Berkeley, and lead author on the study.
“In the West, it's just totally the opposite,” Stephens added. “Even though both places physically have strong connections to frequent fire, the feeling here is that the best thing to do is to try to protect what we have and not allow the return of frequent fire — but that's really difficult when you have unbridled fires just ripping through the landscape.”
A tale of two birds
Spotted owls make their homes in the dense forests of the Western and Southwestern U.S., feeding on flying squirrels and woodrats and nesting in broken-off treetops or tree hollows. Red-cockaded woodpeckers, meanwhile, reside in pine stands in the Southeastern U.S., provisioning nests from nest boxes or hollowed-out cavities in living pine trees and eating insects pried from under tree bark.
Development and logging have robbed both species of much of their former habitat, and their populations have both taken a hit: Partners in Flight estimates the global breeding population of spotted owls to be at 15,000 individuals.
What habitat remains is now largely protected under the Endangered Species Act — but when it comes to fire and forest management, the act has been interpreted in dramatically different ways in the two regions, said paper co-author Leda Kobziar, associate clinical professor of wildland fire science at the University of Idaho.
“In the South, the act is interpreted to support active management through forest thinning and prescribed burning, and in the West, it is interpreted to exclude most fires and active management from protected areas surrounding spotted owl nests,” Kobziar said.
One critical difference is the degree to which active management in red-cockaded woodpecker habitat provides complementary benefits. “In the South, active management is known to reduce wildfire hazards, and it benefits local economies, along with a host of other fire-dependent species. In the West, those complementary benefits are less well-defined,” Kobziar said.
Another part of the reason for the discrepancy is perceived differences in the habitat preferences of the two birds, Kobziar explains. Red-cockaded woodpeckers live in more open, mature pine forests that result when low-intensity natural or prescribed burns limit the development of a forest midstory, where woodpecker predators take cover. Meanwhile, spotted owls generally prefer the dense, multi-layered forests that grow when fire is excluded.
However, suppressing all fires in order to encourage growth of these dense canopies also creates conditions that are ripe for large, severe wildfires that can take out not just the smaller trees, but entire forests, obliterating swaths of owl habitat in the process. The 2014 King Fire, for example, tore through regions of the Eldorado National Forest that were home to a long-term study of the California spotted owl and caused the bird's largest population decline in the 23-year history of the study.
“A key question to be asking is: Where would owl habitats be with more characteristic fire regimes, and could we tailor landscape conditions where these habitats are less vulnerable and more supportive of today's wildfires?” said co-author Paul Hessburg, a research landscape ecologist with the U.S. Forest Service Pacific Northwest Research Station.
The solution would mean, “essentially creating less habitat in order to have more in the long run,” he said.
Fighting fire with fire
Before European settlement, many small- to medium-sized wildfires burned through the forests of the Southeastern and Western U.S., sparked by lightning or intentionally lit by native peoples to produce food, clear land or drive game. These fires would gobble up the dead wood, seedlings and saplings that made up the forest understory, while leaving taller, older trees standing and marked with fire scars recorded in their growth rings that fire ecologists use to track the frequency of historical fires.
In the mountainous landscape of the West, these fires didn't strike uniformly everywhere, to the potential benefit of the owls, Hessburg said. “If I took you back in the way-back machine 200 years ago, you would have seen that fire regimes in the Cascade Mountains differed very much by topographic setting,” he said. “Ridgetops and south slopes would often get pounded with lightning and fires, and so tree cover would be sparse. But in shaded and cool valley bottoms and north slopes, you would see complex layered forests, and some of these would have been incredible owl habitats.”
Targeted restoration thinning and prescribed burning on ridgetops and dry southern slopes where fire used to be a frequent visitor, while leaving valley bottoms and northern slopes to develop into complex forest, could be a way to discourage large wildfires from ripping through vast landscapes, while maintaining owl habitat in a more fire-protected context.
New evidence also hints that owls may not be so dependent on dense understory canopies as once thought, the paper notes. Recent findings indicate that other aspects of forest structure, particularly the presence of large, old, tall trees, may be more important to the owls. These findings hint that prescribed burning and restoration thinning to reduce the size and severity of wildfires may not be damaging to owl habitat, even in the short term.
“We're treating the habitat as if we know precisely what habitat characteristics are preferred. It might be that these birds are tolerant of a broader range of characteristics that would enable things like fuels reduction to protect them from high-intensity wildfires,” Kobziar said.
“The South has melded fire and rare species management in a holistic way, but in the West, we're doing one or the other — (in) most places (where) we do forest restoration, we are trying to avoid owls,” Stephens said. “But the King Fire showed that owls and their habitats are vulnerable to large wildfires. More restoration thinning and prescribed burning could help us keep the habitat that we have now, modify it and actually make it more sustainable in the future.”
Other co-authors on the study include Brandon M. Collins of UC Berkeley; Raymond Davis, Joseph Ganey, James M. Guldin, Serra Hoagland, John J. Keane, Warren Montague, Malcolm North and Thomas A. Spies of the U.S. Forest Service; Peter Z. Fulé of Northern Arizona University; William Gaines of the Washington Conservation Science Institute; Kevin Hiers of the Tall Timbers Research Station; Ronald E. Masters of the University of Wisconsin-Stevens Point and Ann E. McKellar of Environment and Climate Change Canada.
RELATED INFORMATION
- Is fire ‘for the birds'? (Frontiers in Ecology and the Environment)
- Stephens Lab website
Barn Owls: Biological Control
I usually enjoy life and growing things as a farmer, however I was excited in the recent weeks to see the remains of something most definitely dead; owl pellets under an artificial nesting site. After a couple barn owl boxes were installed last year, I have eagerly awaited their occupation. Did you know that a family of barn owls will eat about 1,000 rodents in a single nesting season?
The recent owl pellet observation sparked my interest in researching the benefits of barn owls in agriculture. I found lots of information but focused on a particularly good peer-reviewed article called Agriculture land use, barn owl diet, and vertebrate pest control implications. (Kross, 2016). I will share with you the highlights, but you might want to read the research report yourself.
Research of owl presence at 25 California nesting boxes located mainly on row crops and perennial crops and forage, identified 1044 prey species. Pocket gophers, mice, and voles are generally the most important parts of the barn owl diet. Gopher numbers were highest in owl pellets found near perennial cropping systems but still a significant part of pellets found in annual cropping systems. Although mice are often considered less important as pests than gophers, they can carry pathogens that are a food-safety risk. 99.5% of prey items studied were agriculture pests, therefore owls are likely to provide valuable pest control services for farmers in our area if owl populations are fostered. Barn owls can persist if nesting sites and prey are available. Farmers seem to help provide the rodents, but let's not forget the nesting sites!
Alternative methods for rodent control such as trapping and poisoning can be expensive, labor intensive, and impact non-target species. Installation of nesting boxes to attract barn owls is not a proven method for sustained rodent control in agriculture systems by itself, rather it is best included as a component in an integrated pest management plan. Availability of nests sites appears to be the limiting factor of barn owl population growth in habitats that interface with humans (i.e. Farms and Ranches). Barn owls in the studied area occupied over half of the artificial nesting sites available to them, so installing nest boxes on farms may increase the natural barn owl rodent control.
Take away:
Farmers and ranchers who wish to utilize the low-cost natural predation of rodent pests by barn owls in their agriculture systems or simply attract owls should:
- Provide abundant nest sites, including nest boxes. Funding and plans may be found through contacting your local resource conservation district.
- Increase crop type diversity in proximity to nest sites to include both perennial and annual systems to increase owl hunting efficiency.
- Install nest boxes now for this spring nesting season for best chance of owl occupation in the next 6 months.
Resources:
Read the research article discussed above:
Kross S., Bourbour R., & Mertinico B. 2016. Agriculture land use, barn owl diet, and vertebrate pest control implications. Agriculture Ecosystems and Environment. 223, 167-174. http://sarakross.weebly.com/uploads/8/6/7/7/8677631/kross_bourbour___martinico_2016.pdf
NRCS Barn Owl Information Sheet and Owl box plans https://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcs144p2_063925.pdf
UC Master Gardener Gopher Blog post, ideas for gopher management with great photos https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=29485
UCANR Songbird, Bat, and Owl Houses https://anrcatalog.ucanr.edu/Details.aspx?itemNo=21636 This handy guide explores the benefits of the biodiversity and aesthetics of songbirds, bats, and owls. While written with vineyard managers in mind, anyone interested in learning about nest boxes will find this guide useful. Purchase this booklet at the link above for $15.
Barn owls help clean up rodents naturally
The screech of a barn owl at night may be startling or annoying to some. But others may find their harsh calls satisfying, knowing that barn owls are out, feeding on pesky rodents.
They're fierce hunters with a voracious appetite for mice, voles, gophers, and rats. A family of five barn owls, including two adults and three young will feed on about 1,000 rodents during a season. When they nest twice in a year, that number doubles and you wind up with some good help on rodent control that's safe and free.
So, the next time you hear that eerie, rasping sound at night, don't panic. Instead, think about all the good the owls are doing. Even better, invite a family of barn owls to your property by building a nest box for them and creating a home.
Identifying barn owls. If you're lucky to spot one in an old barn where they're often found (hence their name), they have iconic white heart-shaped faces, white chests, and tan-colored backs with spots. Barn owls are nocturnal and can be recognized by their drawn-out rasping screech. Unlike other owls, they don't hoot. They often shriek when they leave their roost to hunt and make hissing and snapping sounds when startled.
Barn owls have excellent vision and hearing for finding prey in the dark and capturing it with their sharp talons and beaks. They're quiet hunters, flying close to their prey without being heard, due to specialized feathers, making them incredibly good predators. Barn owls are found world-wide and occupy a wide range of habitats, including natural, agricultural, and urban areas, but prefer to hunt in more open areas as opposed to forests. They readily hunt rodent pests in grape vineyards, alfalfa fields, and along levees, making them valuable allies for farmers.
How do you attract barn owls? Barn owls are cavity nesters, including cliffs, trees, and buildings such as barns, so they will readily use nest boxes. Plans for how to build nest boxes can be found in the UC Agriculture and Natural Resources (UC ANR) booklet, Songbird, bat, and owl boxes. This handy guide also shows how to attract insectivorous birds and bats to help control insect pests naturally. Barn owl boxes and plans can be found online or through local sources, such as G. Rohman (photographer). Barn owls begin nesting in February, so now is the time to put up a house before males and females select nest sites. Boxes should be mounted 10 feet off the ground on metal poles to prevent mammal predators from accessing the boxes and feeding on eggs or chicks.
Paint the boxes white to keep them cooler and help prevent weathering and face them northeast. Add some timothy hay for bedding (often sold in small bags in stores for rabbit feed). Wooden nest boxes are generally preferred over plastic ones. Fifty gallon drums can also be used; just remove the top, retaining a lip so the chicks don't fall out, add some hay, and hoist it up on a rafter in a barn and secure it well with a chain. Avoid disturbing nest boxes during the breeding season (February through August), as barn owls will often abandon nests if disturbed while nesting.
Who moves into the nest box? A family of barn owls. Females generally lay four to seven eggs from February to April, which hatch in about 30 days. While they incubate the eggs, the males bring food to the nest. The baby owls fledge in about 10 weeks, but stay around the nest until fall, when they wander off, usually within 30 miles of where they were born. Sometimes a second clutch of eggs is laid in May. Barn owls do not migrate, so tend to stay in an area year-round and will reoccupy a nest box the following year. They generally forage about one to three miles from their roosts. They are only mildly territorial in that they will defend their nests if you get too close. This means that you can put up several nest boxes in an area and expect occupancy from several families. Barn owls generally only live for about two years. Great horned owls are the fiercest predator of adult barn owls (and collisions with cars).
What are they eating? The favored prey of barn owls is rodents, including voles and gophers. Like other owls, they often swallow their prey whole and then undigested bones and fur are coughed up (regurgitated) as owl pellets. These pellets can be dissected and prey readily identified by the skeletons left behind. Farmers appreciate owls and other raptors because they feed on rodents that can damage their crops and irrigation systems (Wildlife Survey).
UC ANR researchers, including Roger Baldwin, UC Cooperative Extension vertebrate pest control specialist, are currently evaluating the economic impact of barn owls for rodent control in agricultural lands. It is important to note that rodents reproduce rapidly so barn owls cannot always keep up with rodent outbreaks and other methods of control might be needed to prevent crop damage (Rodent Control). But, every rodent a barn owl takes is one less we have to deal with!
How about maintenance? Barn owl boxes need to be cared for and cleaned once a year during fall or winter (October to December) as the pellets can quickly fill up a nest box. Doors for accessing the inside of the boxes need to be secured, hinges lubricated, and mounting structures checked during annual inspections. Avoid breathing unhealthy dust when cleaning the house and always make sure no one is home. Although this takes time, the pellets cleaned out might have added value. A Yolo County farmer mentioned he has a buyer for his pellets, which are used for science projects where students dissect them to learn about skeletons and barn owl diets. He read his recent owl pellet invoice noting, “The pellets are graded from small at 10 cents each to premium at 20 cents each and I sold over 100. Barn owls are great!”