Faculty-student research aims to support Wisconsin bluebird population

In an effort to conserve the Wisconsin bluebird population, Professor of Biology Memuna Khan has performed a two-year study researching how to mitigate the destructive behavior of house wrens, tiny birds that can threaten bluebird nest success. According to Khan, house wrens are “cute and lovely” birds that contradict their adorable nature with their mean personalities. They are known to puncture eggs and destroy the nests of bluebirds and other species that they perceive as competitors.

To prevent this destructive behavior, wren guards — devices attached to the front of the entrance hole of bluebird boxes — were invented. The manner in which the devices work is debated. While some believe the devices function by blocking a direct view into the nest box, thus deterring wrens from entering the box. Others, like Khan, believe the guards make it difficult for the wren to access the hole to the nest box.

Scientific studies regarding whether or not these devices are actually effective, however, were scarce before Khan’s research. A concern was that the wren guards also may prevent bluebirds from utilizing their own nest boxes.

Consequently, the Bluebird Restoration Association of Wisconsin, whose mission is to support the conservation of bluebirds, contacted Khan. “(They) approached me to do a rigorous scientific study of wren guards and if they’re effective, so that’s what a couple of students and I did,” Khan says, adding that the project also served to support undergraduate research.

Natalie Davies ’23 of Cedar Grove, Wisconsin, did the study with Khan the first year, while Zach Rowling ’24 of Chandler, Arizona, continued the study the following year. “We created an experiment where we located wren nests and we set up two nest boxes, one with a guard and one without,” Khan says.

The next step was to wait 24 hours to check if the wren got around the guard, and, according to Khan, “you would know this immediately because the eggs inside the experimental boxes would either be punctured or removed.”

The study found wren guards were 50% effective, meaning that the wrens were deterred from entering the boxes about half of the time — a significant improvement from the 99% of nest boxes they otherwise would enter and destroy. Meanwhile, nesting birds, like the bluebird, were able to continue their reproductive efforts more than 85 percent of the time, despite the implementation of the wren guards.

For those interested in using wren guards to support bluebird restoration efforts, Khan says, “If you’re going to use a wren guard with a bluebird nest, you need to be aware and not just fix it and leave; make sure that the bluebirds accept and then cross your fingers that you’ve given them the boost they need.”

Using the results of her research, Khan co-wrote an article with the Bluebird Restoration Association that was published in the North American Bluebird Society newsletter, which has a national readership. She also presented her research at a Green Lake Bird and Nature Club conference.

(Photo: Natalie Davies ’23, left, and Zach Rowling ’24)

Amanda Barlow ’23
Appleton, Wisconsin

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