Jim Knight

MSU Wildlife Specialist

4/7/1999 - BOZEMAN -- Homeowners now can replace their hawk statues and scarecrows with a new weapon to deter birds feasting on garden fruits– ordinary, inexpensive fishing line, says a Montana State University wildlife specialist.

"Every year I get lots of calls from people having problems with birds chomping off new sprouts as they come up in the garden," says James Knight, wildlife specialist for Montana State University Extension Service. "Other people have problems with birds getting into trees and pecking on the fresh fruit just before they’re going to harvest."

In the past, Knight recommended that homeowners use netting or other barriers to keep birds like pesky sparrows and pigeons out. But barriers make harvesting difficult. Repellents such as snake, hawk or owl statues weren’t very successful either.

"The repellents work for a few hours or even a few days," Knight said. "Then before long, the birds are perching on them."

But Knight thinks he might not get as many calls from frustrated gardeners this year if they try a trick with monofilament fishing line that he discovered by chance.

"A few years back, I had some beans in my garden, and I marked one row with some monofilament line," Knight explains.

"It turned out that when the other rows came up, the sparrows chomped off the sprouts as soon as they emerged. But the row underneath the line was untouched."

Next, he put the fishing line over the other rows of beans and found that the birds were repelled.

"Just a single strand of monofilament line suspended directly above the sprouts, tied to stakes at either end of the row, was causing the birds to avoid that area," Knight says.

As the sprouts grew, he simply raised the line to keep it just above the plant.

Knight later tried his idea on his neighbor’s strawberry patch that was besieged with sparrows even though chicken wire covered the patch.

"I suspended the line in rows about six inches apart, and depredation on the berries totally ceased," says Knight. "It also made it easy to harvest the strawberries through the monofilament line."

Knight then found a third use for the fishing line. He stretched two lines six inches apart under the eaves of a house. This prevented swallows from building mud nests there.

"Keep in mind that swallows are protected," Knight says. "That means you can’t destroy their nest once they start building it. But by putting up the line before they begin to construct a nest, you won’t run into that problem."

Knight speculates that the monofilament line deters birds because of its low visibility.

"The line has a characteristic that causes it to appear and disappear from sight – it seems to be continually moving," he said. "With just the slightest movement of the line from a breeze or anything else, there can be major changes in the line’s visibility. I think this is what causes birds to fear it or try to avoid it"

Knight says one drawback to the fishing line is that it becomes brittle when exposed to the sun, making it susceptible to breaking in the wind. He said heavier monfilament lines, such as a 20 pound test, aren’t as likely to become brittle. But weights higher than 20 pounds start to lose their repelling characteristics.