- Author: Hannah Meyer
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.
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.
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.
Growing mandarins in the foothills often produces a tantalizing crop of fruit that delights even the pickiest of connoisseurs, however, it is not produced without difficulty. UCCE Placer/Nevada has collaborated with five local citrus growers to research the effects of pruning to thin canopy and mulching to conserve soil moisture and create a healthier root zone. To learn more about this project, read Citrus Grower Bob Bonk's blog post, Mandarin Growers Test New Practices on the Foothill Farming blog. Research began just over a year ago and here are some of the things we have learned so far.
Mulch under citrus trees helps maintain soil moisture, reduces soil temperatures, and can effectively manage weed growth.
Methods: Mulch is best applied when the soil is saturated. Typically mulch is applied in March/April in this region but can be applied later if soil is irrigated to saturation level. Mulching is most effective for weed suppression when either little to no weed emergence has occurred, weed whacking, or herbicide spray is implemented first. Mulch alone reduces weed growth. Mulch applied over builder's paper or 6-8 sheets of newspaper then saturated to conform to the ground is even more effective. Fertilizer is best applied before mulching.
Materials: A 50/50 wood chip and horse manure blend is used in the research trials but either one can be used on its own. Composted manure alone decomposes rapidly, a mix of manure with wood chips will last longer. Wood chips last longer than either the wood chip/manure mix or manure alone but will provide little to no nutrient value to the tree.
We have observed that often irrigation with overhead sprinklers does not penetrate dense tree canopies and may lead to water stress. Tensiometers, which measure soil moisture, were installed in citrus orchards in summer 2017. They showed that overhead irrigation water was not reaching the ground under dense canopies, causing water stress in hot weather. As a result of some of this research, several commercial citrus growers have modified irrigation practices or are changing irrigation systems to mitigate water stress.
Looking to the future:
Soil temperature can affect root activity so beginning this year soil temperature are also being monitored throughout the research project. Citrus growers are attending workshops, field meetings, and learning what the orchard trials are teaching us. Many are implementing new methods and practices in their citrus operations. Citrus trials will continue at least through 2019. Look for more information in future blogs.
Commercial growers are invited to participate in a Composting & Mulching Workshop on Thursday, May 31st, 9 AM to 12 noon, register at this link. http://ucanr.edu/survey/survey.cfm?surveynumber=24853