New barn owl nesting boxes appearing in Grand Terrace parks are part of an innovative City effort to address a familiar maintenance problem by giving nature a chance to help.
The City of Grand Terrace is installing 12 barn owl nesting boxes at several park locations as part of an environmentally friendly approach to controlling gophers and other rodents. Rather than relying solely on traditional pest-control methods, the program provides habitat for native barn owls and encourages these natural predators to live and hunt in areas where rodents damage turf, landscaping and irrigation systems.
The City is not bringing owls into Grand Terrace or releasing them in the parks. Barn owls already live throughout Southern California. The nesting boxes simply provide suitable habitat and allow the owls to decide whether to use it.
Barn owls are highly effective nighttime hunters whose diet consists primarily of small mammals, including mice, rats, voles and pocket gophers.
That appetite increases during nesting season, when two adult owls may be hunting not only for themselves but also for several growing young. Research in California agricultural settings has documented barn owl families capturing large numbers of rodents over the course of a year, although actual numbers vary considerably depending on prey availability and family size.
For Grand Terrace, that natural behavior presents an opportunity.
Gophers create an ongoing maintenance problem in City parks. Their burrowing damages turf and landscaping, can interfere with irrigation systems, and creates holes and uneven surfaces that City employees must continually repair.
Encouraging native predators gives the City another tool for putting pressure on the rodent population while potentially reducing some of that damage and maintenance work.
Barn owls are cavity nesters, but they do not excavate their own nesting cavities. Historically, they used hollow trees, rock cavities and similar protected spaces and later readily adapted to barns and other structures.
As development has reduced some natural nesting opportunities, properly designed nesting boxes can provide replacement habitat.
Whether Grand Terrace's boxes are ultimately occupied is entirely up to the owls. Installing a nesting box does not guarantee an owl will move in, and some boxes may take several seasons to become established.
That is why the City's program will involve more than simply installing boxes and walking away. Appropriate placement, inspection, maintenance and monitoring will be important parts of determining how well the program works.
The program also makes sense as a practical experiment in reducing City maintenance costs.
The owl boxes represent a relatively minor investment with a long useful life. Spread over an estimated ten years, the entire 12-box program needs to save only about 19 staff hours per year—or roughly 22 minutes of staff time per week citywide—to offset the investment through labor savings alone.
That calculation does not include potential savings from reduced turf damage, irrigation repairs, pest-control treatments, replacement materials or other costs associated with gopher activity.
Every hole that does not have to be filled, section of turf that does not have to be repaired, and irrigation line that escapes damage represents additional savings.
The City does not need every box occupied or every gopher eliminated for the program to provide value. The threshold is much simpler: can natural predators reduce enough damage and maintenance work over the life of the boxes to justify a relatively small investment?
The amount of avoided staff time necessary to reach that threshold is remarkably small.
The program also complements the City's broader approach to living responsibly alongside wildlife.
Rodenticides can affect animals other than the rodents being targeted. A poisoned rodent may subsequently be eaten by an owl, hawk or other predator, creating the potential for secondary poisoning. Improperly accessible bait can also create risks for pets and other wildlife.
Encouraging predators offers another way to control rodents naturally while potentially reducing reliance on chemical controls.
The City will coordinate its pest-control practices with the owl-box program so that efforts to eliminate rodents do not unnecessarily put the predators being encouraged at risk.
The boxes are not intended to replace every other form of pest management. Instead, natural predation becomes another component of a broader, integrated approach.
The potential benefit does not necessarily stop at the park boundary.
Barn owls range beyond their nesting sites when hunting. A box in a City park may provide a home base, but the owl's hunting territory can extend into surrounding neighborhoods, landscaped areas, vacant properties and other open spaces.
That means rodents taken by owls using City nesting boxes could include gophers damaging residential lawns as well as mice and rats elsewhere in the surrounding neighborhood.
The City is essentially using strategically located public property to provide habitat for native predators that can operate across a much larger area.
Twelve nesting boxes therefore should not be viewed simply as 12 isolated pest-control devices. If even a portion become established nesting sites, they could support predators hunting across multiple areas of the community.
Barn owls may also be only the beginning.
The City is considering adding raptor perches at appropriate locations in the future. These relatively simple elevated structures provide hunting and observation points for hawks and other native birds of prey.
Combined, owl boxes and raptor perches could make City parks and open spaces more useful to both nighttime and daytime predators.
As with the owl boxes, the City would not introduce animals into the community. It would simply create suitable habitat and hunting opportunities for native wildlife already present in the area.
There are practical limitations to the program.
Not every nesting box will necessarily attract an owl. Boxes can occasionally be occupied by other animals or insects and therefore require periodic inspection and maintenance. Location matters as well; boxes should be positioned with suitable access to hunting areas while considering roads, park activity and other wildlife.
The City will be able to monitor occupancy and gopher activity over time to determine whether the approach is producing results.
If boxes become active nesting sites, monitoring can potentially include nesting activity, the number of young produced and even owl pellets, which can provide information about what the birds are eating.
That gives the City an opportunity not simply to install the program, but to learn from it and adjust the approach based on what actually works.
The program also offers benefits that are harder to measure in dollars.
Providing nesting and hunting opportunities for native raptors helps maintain a functioning local food web. Rodents that otherwise become a maintenance problem become prey for animals that naturally depend upon them.
The boxes can also provide an educational opportunity. Residents and children may have a chance to observe native wildlife close to home and learn firsthand about predators, prey and the role different species play in the local ecosystem.
Barn owls pose little risk to people or ordinary household pets. Despite their large wingspan, they generally weigh only about one to one-and-a-half pounds and primarily hunt small rodents. As with any wild predator, however, very small animals should not be left outdoors unattended, particularly at night.
Residents can also help make natural rodent control more effective by securing garbage and pet food, avoiding unnecessary use of rodenticides and allowing wildlife to remain wild.
The City's approach is straightforward: where nature can safely and effectively help solve a maintenance problem, Grand Terrace should take advantage of it.
Barn owls, hawks and other raptors were controlling rodent populations long before there were City parks. Providing appropriate nesting and hunting habitat gives those native predators an opportunity to do some of that work for us.
Owl boxes are not a guaranteed solution. They will not automatically attract owls, they will not eliminate every gopher, and they require thoughtful placement and continued maintenance.
But they do not need to eliminate the problem to succeed.
If the program reduces gopher activity, saves even a modest amount of staff time, limits damage to turf and irrigation systems, reduces reliance on chemical controls and provides additional habitat for native wildlife, the City and surrounding neighborhoods all stand to benefit.
And for Grand Terrace residents, there may be another benefit that is harder to put on a spreadsheet: the opportunity to look up after sunset and see one of the community's native predators quietly doing exactly what nature designed it to do.