Nature Lab

Checking Barns and Boxes

Biologists monitor barn owl nests in southwest Missouri

MDC has tracked American barn owl populations since the 1970s, when the species was listed as rare in the state. The type of monitoring has varied over the years, at times accompanied by outreach for installing nest boxes. In 2015, MDC Natural History Biologist Rhonda Rimer and colleagues began surveying for barn owls in buildings and nest boxes on conservation areas and private land in southwest Missouri.

“We wanted to help conserve the species,” Rimer said. “Collecting information — when the owls were showing up, how many eggs they were laying, how many young were fledging, whether nest boxes were helping or not — was a good place to start.” 

As word of their endeavor spread, more landowners invited them to keep track of owls nesting on private properties, some even checking the nests themselves. In time, more than 40 sites were being monitored across 11 counties. Graduate students from Missouri State University joined in, collecting owl pellets to study their diet and putting up cameras to watch their behaviors. 

The data showed that nests in boxes were more successful than nests elsewhere. Footage from the cameras showed why. Raccoons, snakes, and other predators were raiding the nests. Those on barn ledges or open floors were hit the hardest. 

“We saw how hard the parents will fight to defend a nest,” Rimer said, “but when nests are in an open area, it’s difficult. When the owls have a box, a defendable space, they are more successful at protecting their nest and young from predators.” 

The team has now deployed 64 nest boxes. As of 2021, barn owls are no longer a Missouri species of conservation concern; the state’s population has increased and appears stable. Nest boxes were not the only factor, but they helped. To maintain the population, conservation efforts must continue. The owls’ grassland habitat must be cared for, and nest boxes can still give them a needed boost. 

“Conservation doesn’t have to be complicated,” Rimer said. ”It is within the reach of regular people to make a difference. Barn owl boxes are easy to put up. It’s something people can do. It’s not an impossible mission.”

At a Glance

Barn owl nests in southwest Missouri were checked regularly from 2015 to 2023. Less intensive monitoring continues today.

Findings:

• Barn owls nest in varied places in barns (lofts, ledges, old equipment, conduits, etc.)
• Most nest from March to June but may nest any month of the year 
• Nests are often plundered by predators
• Nests within boxes are more successful

Learn more at short.mdc.mo.gov/oNX