In one of many attempts to stop pesky birds from leaving messy droppings, several Main Street Ames businesses have had varied results with a new high-tech device.

Mark Peterson, owner of Emerhoff’s Footwear, 215 Main St., ordered ultrasonic devices to keep the birds away. The devices arrived late last month. Peterson said the contraptions were installed on downtown light poles immediately.

The four machines emit a shrilling sound that is supposed to annoy the birds nesting in trees in the downtown area. Peterson said the instrument’s setting can be changed to sounds that repel anything from insects to large animals. However, he said, the sound is undetectable by humans or domesticated animals.

The instruments, which are located at Ames Silversmithing, Brown’s Shoe Fit Co., Walt’s Hallmark Shop and Olive’s Clothing Store, all downtown businesses, are activated at dusk, when the street lights turn on.

Charlotte Arends, manager at Walt’s Hallmark Shop, said she has noticed fewer bird droppings, but she is not sure if the results are from the devices or the cooler weather.

Arends has cleaned the sidewalks only once since the devices were put in place — for the Ames High School Homecoming parade.

But some businesses have seen little progress. Karen Youngberg, co-owner of Ames Silversmithing, said her sidewalk must still be cleaned every day, even though one of the devices is located near the store.

Youngberg said she has also heard complaints about the sound the devices make.

Peterson said the pulsating sound is annoying and constant. He said it sounds like locusts.

The downtown businesses will have to choose between the annoying sound and the smell of the bird droppings. Peterson said he has not talked to anyone downtown who has said the droppings have hurt business, but he said the “smell is more of annoyance.”

Although the reaction is mixed, Peterson said, the devices may not be a long-term solution because the birds can become too accustomed to the sound.

Businesses are giving the devices a 30-day trial period.