Final Report for FW09-038
This project significantly increased predator habitat by establishing nesting habitat for raising young and perches for hunting rodents. We intend to continue installing several barn owl boxes each year. In addition, we have began installing nest boxes for American Kestrels.
The following outcomes were observed:
1) Occupancy in the nesting boxes by barn owls was minimal the first season and slowing increased each season.
2) The owl nest boxes were not just used by barn owls. Screech owls were common in boxes, but no screech owl nests were observed. American Kestrels used boxes for nesting sites, indicating a lack of suitable nesting sites for kestrels in the area.
3) Using owl boxes is a long-term investment. The owl population does not establish immediately. Rather the populations build over time.
4) Perches were used immediately and extensively by raptors. Owls were often observed using the perches at night, and kestrels and hawks during the day.
5) Rodent activity near perches was reduced immediately.
6) Since the nest boxes did not have full occupancy immediately, supplemental rodent control management was required. It appears that as owl populations increase, the amount of rodent control management activities, and associated expenses, will also decrease. However, a longer study is required to fully research this relationship.
7) Outreach and education efforts were very successful. Many presentations were made to local growers. Several local and nationally distributed articles were written about using owls for rodent control.
1 ) Evaluate the effectiveness of Barn Owl boxes and raptor perches as a sustainable method to control rodents in orchard systems.
2) Compare the cost effectiveness of raptors for rodent control with conventional methods of poison baiting and trapping.
3) Educate the 400+ orchardists in the Mid-Columbia region on the use of raptors for rodent control, and thereby reduce the amount of poison baits applied in orchards.
Two orchards of similar age and size were selected. At one orchard 25 barn owl boxes and 40 raptor perches were installed. We found that using 2 inch black iron pipe worked best for mounting poles for barn owl boxes. The metal pipe prevents raccoons and other predators from climbing the pole and eating the barn owl babies out of the next box.
Rodent populations were assessed using a “mow and count” method described by Dr. Dan Edge (chair of Wildlife Dept at Oregon State University). Basically we mowed the orchard and came back the next day and counted gopher mounds. This method worked really well for identifying gopher populations. The mounds were fresh and easy to see in the fleshly cut grass. Voles were counted using the “Apple Sign Test” standard. We placed a slices of apple in a foot-long piece of 4” PVC pipe. We then came back after 48 hours and looked to see if the voles had eaten any of the apple. If you wait longer than 48 hours the apple starts to shrink and rot, and it is hard to see vole feeding unless they feed a lot.
The use of barn owl boxes appears to be a viable tool for rodent control in orchards. However, the owl population does not establish immediately. Rather the populations build over time.
It is not known how much savings will be generated by using barn owl boxes, as the nest boxes did not have full occupancy immediately, which meant supplemental rodent control management was required. It appears that as owl populations increase the amount of rodent control management activities, and associated expenses, will also decrease.
On my own farm we have reduced using hand-applied rodenticide bait by 50% in the orchard with barn owl boxes. This is a savings in material and labor of approximately $23/acre. In addition, we improve worker safety by preventing contact between workers and the rodenticide.
Education and Outreach
Mike Omeg spoke at several local tours and workshops about barn owls. In addition, local and national press published articles about the use of barn owls in rodent control. Over 300 growers total attended these presentations.
Good Fruit Grower magazine- August 2009
Rural Lite magazine - October 2009
Columbia River Toxics Reduction Newsletter- Febuary 2010
NRCS Legacy of Conservation story in NRCS newsletter- May 2010
Gorge Living magazine- Spring/Summer 2010
Good Fruit Grower magazine- September 2012
Education and Outreach Outcomes
Upon learning of the project and owl boxes, many orchardists in the area began purchasing boxes for their orchards. Tuck Contreras, the local builder who made the owl boxes, received orders for over 300 boxes from local growers over the two years of the project. One grower ordered 50 boxes for his operation. In addition, growers were very interested in learning about how rodenticide use can impact owls and other raptors, and many of them reported they changed the type of rodenticide they used to one that is less toxic to raptors.
Recommendations for other growers wanting to use raptors for rodent control in orchards:
Get a well-made owl box. Use plywood and good quality paint. Owls use the boxes for many years. We have observed cheap boxes falling apart in the weather quickly.
Perches are an excellent way to encourage owls to hunt in your orchard. We now place perches in problem areas. The perch reduces the rodent activity in the area.
If you have trouble with gophers, scout your orchard right after you mow. This will allow you to place rodenticides in targeted areas. Or, even better, place a perch!