Got mice? Bring in the owls!

By Murray Schneider

It’s not the best kept secret that each spring a mother Great Horned owl returns to the eucalyptus tree situated yards from the Elk Street Glen Park Canyon entrance, perches among its burnished branches and nurtures her chicks in a nest that is visible to battalions of canyon visitors.

Richard Craig prior to installing his new barn owl house on Berkeley Way/Glen Canyon.

But if one walks along the rim of the canyon, say, along Turquoise Way, Crags Court and Berkeley Way, you’d see owl dwellings of a different sort, man-made ones constructed from plywood that stare over yellow-eyed grass punctuated coincidentally by owl clover, a rare California native plant that grows only in two other places in San Francisco – Bernal Hill and the Bay View

The recently installed owl houses, four in number, have been secured in trees by the Friends of Glen Canyon Park using six-inch log bolts, and they loom high above the canyon floor, serving an environmentally friendly purpose.

Each is designed to attract barn owls with a hole-size so small that its predator, the Great Horned owl, cannot enter and prey upon owlets.

“We have a rodent problem,” says Richard Craib, president of Friends of Glen Park Canyon. “Gophers and voles cause destruction, burrowing into our cellars and damaging our gardens.”

Craib hopes that by domiciling barn owls 14-feet high in canyon Monterey pine trees, they’ll reduce the rodents.

A resident of Diamond Heights for 47 years whose backyard abuts the highest slopes of the canyon, Craib is as knowledgeable of canyon ecology as he is conversant with home building.

Craib worked construction his entire life, but high-rise office buildings are more his métier than are diminutive tree houses for nocturnal birds of prey. He’s put the four barn owl houses only minutes from his home and placed each in strategic locations to thwart troublesome home invasions from field mice and rats.

Why four owl abodes and why so spread out? An owl will not hunt directly below its nest for fear of attracting the attention of other winged predators, and barn owls are noisy at night during breeding and nesting seasons.

Rich Craib looking up at his newly installed owl house.

“As these owls take up residence and proliferate,” Craib says, “they can catch many of the rodents that cause us grief.

The best-laid plans of man, however, may not catch many mice.

“Given the explosion of rodents due to the unusual rains,” says Randy Zebell, City natural areas gardener, “Rich’s owl houses are an interesting experiment.”

Zebell stood beneath the Craigs Court owl house. “Barn owls are elusive,” he added. “Only when Rich cleans out the houses for confirming nesting material, will we know if he’s been successful.”

A canyon caretaker with a long history of partnering with San Francisco’s Recreation and Parks Department, Craib insists the inimical rodenticides activate laws of unintended consequences, harmful to both humans and critters.

“Rat poisons cause a secondary problem,” he says. “They indirectly kill birds and mammals that eat the rodents, thus doing away with the very animals that can help us solve the rodent problem.”

Zabell agrees with his canyon partner.

“Herbicides are always a last resort,” Zebell says. “Rec and Parks endorses integrated pest management.”

An owl house.

Any vigilant birder with binoculars who gives a hoot can prove Rich Craib correct, as wise as any old owl.

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3 Comments

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3 responses to “Got mice? Bring in the owls!

  1. If more owl-houses in the neighborhood would be a benefit (and my neighbors did just have a rat-man in to clear out some) I’d be glad to have one in my redwood on Arbor St. Email me at sydney@eceteacher.org if you (Mr. Craib) think that’s a good idea.
    Cordially, Sydney Clemens

  2. Glen Park resident

    I hope this works. If not, I’ve found RatZapper (has batteries) works to get rid of the mice and rats.

  3. Thanks for posting about the rat zapper (it gets good reviews on Amazon too). We just got the results for the autoposy back for the great horned owl that died in November in Glen Park – due to rat poison. 😦 Don’t use poison – it can live in rats for up to a week, and will kill large birds, pets, and can hurt kids.

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