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Help Swallows and Bluebirds Thrive

By Heath Keirstead | June 3, 2021

Tricks and Tips to Deter House Sparrows

Two House Sparrows sitting on a rock wall. Photo: Lip Kee CC BY-SA 2.0
House Sparrows can be found on every continent except Antarctica. They aggressively take over the nests of swallows and bluebirds. Photo: Lip Kee CC BY-SA 2.0

House sparrows, originating in Europe, were introduced to the U.S. in 1868 for pest control (1). Although their numbers declined by 84% between 1966 and 2015 (2), they are considered by many a pest because of their aggressive nesting behavior. They will attack swallow and  bluebird mothers who have built nests, then build their own nests right on top of the dead mother and her eggs.

If you have nest boxes for swallows or bluebirds, you may have house sparrows too. I checked in with Neighborhood Naturalist’s Don Boucher about this problem, and he shared a few suggestions.

Weighted Monofilament

Dangling monofilament with weights around the hole works and/or on the roof because sparrows are weak flyers and flutter when they approach the box. The strings make them anxious. Whereas bluebirds and swallow are such strong flyers that the swoop in, and brake before they land on the box or on the hole.”

Mylar Sparrow Spookers

Sparrow spookers are mylar strips that are dangled above the box’s roof and many sparrows are afraid to land near it but bluebirds and swallows don’t really care. But it’s a maker project that will take more time. Dangling old CDs above the box seems to work.”

Small Slot/Hole

“For Violet-green Swallows (most common) a box with an oval slot, 2.5 in. wide x 1.25 in. high, is too narrow for sparrows. Tree swallows need a larger hole than Violet-green. Tree Swallows is just a round hole, 1.5 in. It’s better for swallows to have a 5 in. wide nest box to accommodate their long wings. Barn Swallows and Cliff Swallows don’t use cavities because they make their own mud nests.”

Thanks for sharing all that helpful information, Don!

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