- Author: Kat Kerlin, UC Davis
Natural habitat maximizes the benefits of birds for farmers, food safety and conservation
A supportive environment can bring out the best in an individual — even for a bird.
After an E.coli outbreak in 2006 devastated the spinach industry, farmers were pressured to remove natural habitat to keep wildlife — and the foodborne pathogens they can sometimes carry — from visiting crops. A study published today from the University of California, Davis, shows that farms with surrounding natural habitat experience the most benefits from birds, including less crop damage and lower food-safety risks.
The study, published in the Journal of Applied Ecology, was conducted at 21 strawberry fields along California's Central Coast. It found that birds were more likely to carry pathogens and eat berries without surrounding natural habitat.
The authors said a better understanding of the interplay of farming practices, the landscape, and the roles birds play in ecosystems can help growers make the most out of wild birds near their fields.
“Bird communities respond to changes in the landscape,” said lead author Elissa Olimpi, a postdoctoral scholar in the UC Davis Department of Wildlife, Fish and Conservation Biology at the time of the study. “As birds shift in response to management, so do the costs and benefits they provide.”
The single most important driver
The study looked at how different farming practices influenced the costs and benefits that wild birds provided on the strawberry farms. The scientists combined nearly 300 bird surveys and the molecular analyses of more than 1,000 fecal samples from 55 bird species to determine which birds ate pests, beneficial insects and crops, and carried foodborne pathogens.
They also ranked birds to see which were more likely to bring benefits or costs to farmlands. Barn swallows, for instance, got a “gold star” in the study, Olimpi said. Their mud nests are commonly seen clinging to the underside of barn eaves, from which they fly out to swoop over fields, foraging on insects.
But rather than resulting in a list of “good” and “bad” birds, the study found that most bird species brought both costs and benefits to farms, depending on how the landscape was managed.
The presence of natural habitat was the single most important driver differentiating a farm where wild birds brought more benefits than harm.
“Nature is messy, and birds are complex,” Olimpi said. “The best we can do is understand how to take advantage of the benefits while reducing the harms. Growers will tell you it's impossible to keep birds off your farm — you can't do that and don't want to from a conservation perspective. So how can we take advantage of the services birds provide?”
Win-wins for birds and farms
The study is one of several publications from UC Davis Professor Daniel Karp's lab highlighting the environmental, agricultural, and food safety impacts of conserving bird habitat around farms. A related study in 2020 found that farms with natural habitat attracted more insect-eating birds — and fewer strawberry-eating birds — so that farmers experience less berry damage on farms with more habitat nearby. Such habitats also bring greater numbers of bird species to the landscape.
“All together, these studies suggest that farming landscapes with natural habitat tend to be good for conservation, farmers, and public health,” said Karp.
Additional co-authors of this study include Karina Garcia and David Gonthier of University of Kentucky, Claire Kremen of UC Berkeley and the University of British Columbia, William E. Snyder of University of Georgia, and Erin Wilson-Rankin of UC Riverside.
The research was funded by the USDA and UC Davis Department of Wildlife, Fish and Conservation Biology.
/h3>/h3>/h2>The Master Gardeners would like to invite you to join us for a fun evening of learning about native pollinators and how you can attract them to your garden. This presentation will focus on using California native plants and pollinator friendly practices to create habitat for these fascinating species.
When: May 26, 2020 6:00-7:30 p.m.
Where: Zoom
How: Register at: http://ucanr.edu/virtualpollinators/2020
Speaker: Chris Howington, Natural Resources Conservation Service (USDA-NRCS)
Watch the Live Broadcast
To watch the presentation live, make sure Zoom is installed on your device. You'll receive the Zoom link just a few days before the presentation in an email, as well as slides for you to print so you can follow along. Please do not share this link with others.
If you don't have Zoom or want to watch the presentation at another time, it will be available on our YouTube Channel at a later date. http://ucanr.edu/uccemgyoutube
- Author: Kara Manke
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
Advice for the Home Gardener from the Help Desk of the
UC Master Gardener Program of Contra Costa County
Client's Request (from telephone conversation): Help!... I'm growing tomatoes in an enclosed courtyard. I'm now seeing tomatoes disappearing and some with gnawed portions of low hanging tomatoes. I've heard a lot about voles being quite prevalent this year. Do you think it is voles? Other than the disappearing tomatoes and gnawing, I haven't really seen signs of other “animals”.
MGCC Help Desk Response: Thank you for calling the UC Master Gardener Program Help Desk this morning with your question about your disappearing tomatoes.
On the other hand, rats are excellent climbers and though somewhat larger, look similar to voles. (Voles can be up to 8 inches long, including the tail, and they have a short tail. While rats are much larger than the common house mouse or meadow vole, a young rat is occasionally confused with a mouse. In general, very young rats have large heads and feet in proportion to their bodies, whereas those of adult mice are proportionately much smaller).
Reducing the rat population should be the first step in protecting your tomatoes. Sanitation and making your courtyard less hospitable to rats, can go a long way to reducing the population. If you have bird feeders, either remove them or clean under them daily and take them inside at night. Also, talk with your neighbors about reducing rat habitat, as this is usually a neighborhood-wide problem. (Rat habitat outside of your courtyard might include woodpiles, moist areas in and around gardens, and dense vegetation such as ivy.)
Trapping can also work to reduce the population, but it is difficult to make a permanent dent in the population through trapping alone. Snap traps are the best traps to use as long as you can place them where other animals (squirrels, opossums, and birds as well as your dog or neighbors' cats) can't get to them. For roof rats, the traps should be placed in off-the-ground locations such as branches or fences.
If you use traps, check them frequently for dead rats. Do not touch rodents with your bare hands. Make sure you wash your hands thoroughly after handling traps. Dispose of dead rats by burying them or by placing them in a sealed plastic bag and putting them in the trash.
In the meantime, physical barriers can be used to protect your tomato plants directly. One approach is to erect a 1 foot tall barrier using metal roof flashing (obtainable at the hardware store) all the way around the planting bed. Rats are unable to gain traction on the slippery surface. Alternatively, you could build a small-mesh (no larger than 1/4 inch holes) enclosure around the bed or around each plant. Since rats, especially roof rats, are excellent climbers, the wire mesh enclosure would need to go up the sides and across the top of the plants.
We do not recommend use of rat poisons, especially out of doors, due to risk of harm to wildlife and pets either by eating the poison directly and/or indirectly in eating the rat.
For more information on rat identification and management, see: http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn74106.html
And for information on voles see: http://ipm.ucanr.edu/PMG/PESTNOTES/pn7439.html
Hope this information helps you eliminate those disappearing tomatoes. From the inquiries Master Gardeners have received about rats this year you are not alone.
Please let us know if you have further questions.
Good luck with your tomatoes!
Help Desk of the UC Master Gardener Program of Contra Costa County (MCW)
Please Join us at "Fall for Plants" on September 9 for the workshops and the plant sale, Registration is optional, but it'll get you a free plant from the sale. Hope to see you there.
Note: The UC Master Gardeners Program of Contra Costa's Help Desk is available year-round to answer your gardening questions. Except for a few holidays, we're open every week, Monday through Thursday for walk-ins from 9:00 am to Noon at 75 Santa Barbara Road, 2d Floor, Pleasant Hill, CA 94523. We can also be reached via telephone: (925)646-6586, email: ccmg@ucanr.edu, or on the web at http://ccmg.ucanr.edu/Ask_Us/ MGCC Blogs can be found at http://ccmg.ucanr.edu/HortCoCo/ You can also subscribe to the Blog (http://ucanr.edu/blogs/CCMGBlog/).
- Author: Patrick Moran
Editor: Guy B Kyser
The giant invasive grass arundo (Arundo donax), one of the weeds targeted under the USDA-ARS-funded Delta Region Areawide Aquatic Weed Project (DRAAWP), has been re-acquainted with one of its natural enemies imported from arundo's native range. A tiny insect called the arundo armored scale (Rhizaspidiotus donacis) has been successfully released in the Sacramento River watershed and in the Delta.
Arundo forms dense stands across at least 10,000 acres in California, and over 100,000 acres in other arid riparian areas such as the Lower Rio Grande Valley of Texas and Mexico. Other control methods such as herbicide application, mechanical removal, mowing or burning have been used to reduce arundo populations in California, costing tens of millions of dollars. However, arundo is a tough plant and takes advantage of human disturbance and fire in riparian habitats along creeks, sloughs, rivers and reservoirs. Arundo populations in California thus exceed the capacity of these other control methods. In the absence of control, arundo consumes and wastes scarce water – a single plant can consume as much water as corn when growing in moist soil under hot, sunny conditions. Dense arundo stands block access to water for irrigation and recreation, and also obstruct flood control structures such as drainage ditches. Arundo also displaces native plants and animals and alters geomorphology and water flow dynamics in riparian habitats in ways that make it difficult for the natives to come back even if the arundo is controlled.
Biological control of invasive weeds focuses on the characterization, release and evaluation of insects (or plant pathogens) from the weed's native range into areas where the weed is non-native. The arundo armored scale was collected originally in southern France, Spain, and Italy. Studies by Spanish collaborators showed that, even in its native range with its own natural enemies, the arundo armored scale reduces shoot growth and rhizome size by 50%.
Biological control agents undergo rigorous testing to ensure they are not a threat to native plants or crops. After a permit review process, the USDA granted a permit for field release of arundo armored scale in 2010. (This is one of two insects that have been released for biological control of arundo in North America.) Since 2011, this biological control agent has been released in the Lower Rio Grande Basin. Initial releases of this agent in California began in 2014, and it was found that the scale insect had become established at one site in the northern Sacramento Valley by November of that year.
Armored scales are small insects that spend most of their lives in an immobile state, covered by their waxy secretions (‘armor'). Adult females produce ‘crawlers' that disperse locally (typically just a few feet) to find new buds coming up from the arundo rhizomes or lateral shoot buds above ground. The crawlers then lose their legs and antennae and insert their stylet-like mouthparts into the arundo tissue to feed on the fluids in the plant's vascular system. Crawlers molt to a second immature phase, and about six to eight weeks later, short-lived adult males emerge from their armor and mate with the immobile adult females. The females continue to feed and slowly develop embryos. A new generation of crawlers then emerges from the females. The life cycle takes four to six months.
Top row, left to right: Tiny (0.5 mm) crawlers emerge from females and settle on rhizomes or lateral shoots. Second-instar immature scales continue to feed and expand. Winged adult males emerge from their oyster-like scale covering. Females (armored scale cover removed) are shriveled and skinny right after molting. Mature females are plump and turn a darker color when they are full of crawlers ready to emerge. Bottom row, left to right: Adult females form aggregations on arundo rhizomes and shoots. The presence of armored scale populations causes shoot distortion and reduces both shoot growth and rhizome size.
In 2015, we tested a new release technique using arundo ‘microplants'. We soaked arundo shoot fragments in water for one month, then planted them in pots where they produced new shoot buds and roots. Armored scale crawlers were released onto the microplants. After about six months, we planted the infested microplants at field sites in the Delta – Andrus Island on the Sacramento River, and at Big Break near Oakley – and along Stony Creek in Glenn and Butte Counties north of the Delta. We established the microplants adjacent to large arundo shoots, and we cut off some of the established shoots to encourage production of new rhizome buds and lateral shoots. We watered the microplants as needed to keep them alive for about 6 months.
Left to right: Microplant with gelatin capsules used to isolate scale crawlers from females (capsules had been opened and crawlers poured onto the base of the plant). Greenhouse bench with arundo microplants. Field plot with arundo shoots cut back to promote new shoot and rhizome growth. Base of an arundo shoot at the field site (arrow indicates location of adult female scales that developed from crawlers that had previously came out of the females on the microplants.
Almost one year after planting, in November 2016, we sampled arundo rhizomes and shoots from the areas where the now-dead microplants were placed. At the Sacramento River site, 150 females were found, and at a site on Stony Creek in Butte County, 72 females were found. The females were placed in gelatin capsules to capture crawlers. A total of 1,668 crawlers emerged by early January 2017. Since there are still many more arundo shoots around the microplant sites, these results indicate that the arundo armored scale has established reproductive populations at three sites in California. This is the first establishment of this biocontrol agent in the state. Additional releases are planned throughout the Delta and surrounding watersheds. Along with the arundo wasp (Tetramesa romana), the arundo armored scale is expected to significantly reduce the potential for arundo to grow, disperse and form damaging populations that threaten water resources.
This work is conducted under the USDA-ARS-funded Delta Region Areawide Aquatic Weed Project (DRAAWP). This portion of the project is led by Dr. Patrick Moran (Patrick.Moran@ars.usda.gov) of the USDA-ARS Exotic and Invasive Weeds Research Unit, Albany, CA. Dr. Moran is working with a postdoctoral researcher, Dr. Ellyn Bitume (Ellyn.Bitume@ars.usda.gov), on this project. Contact us if you have questions. The Sacramento-San Joaquin Delta Conservancy (Beckye Stanton) is collaborating with USDA-ARS to identify field sites in the Delta, connect with landowners, and integrate biological control with their chemical arundo control program. Dr. Moran cooperates with landowners and local Reclamation Districts to obtain access to field sites.