Boo! Modern-day scarecrow shoos birds

DAVIS
October 31, 2005 8:33am

Central Valley almond growers, who can lose as much as $1,000 worth of nuts per acre to hungry crows, may find relief with an electronic “scarecrow” developed by researchers at the University of California, Davis.

Secreted among the branches, the gadget broadcasts crow distress calls, discouraging the birds from landing in almond trees. The units emit a variety of distress calls, so the clever crows don't become accustomed to the warnings, something that's been a drawback with similar systems in the past.

"One of these units, which covers four acres, costs about $125 to build and would likely be less to produce commercially," says agricultural engineer Michael Delwiche. "We estimate the units could result in savings of between about $30 and $60 per acre."

Crows can cause damage ranging from $130 to $1,000 per acre in a single season in California almond orchards, he says.

The unit features a stainless steel plate on which the speaker and circuitry are mounted. It plays four different 25-second-long distress calls, pausing for 12 minutes between each call and automatically switching off at dusk and back on at dawn to save power.

The researchers tested 36 of the broadcast units in commercial almond orchards for 10 weeks during the second year of the study and compared the damage levels with first-year results when the units were not used. When the units were activated, large flocks of crows approached the source of the calls, circled overhead while calling and then flew away.

A decrease in the crow population the second year of the study accounted for some decrease in crop damage, but the broadcast units appeared to be responsible for a further decrease in crop damage. The researchers found that the crows did not grow accustomed to the recorded calls until near the end of the study, and they are optimistic that the period of effectiveness can be stretched to span the eight-to-10-week period when almonds are vulnerable to crow damage.