Mist Netting at JK Black Oak Reveals Bat Diversity and Surprises

Volume 30 Issue 4, Fall 2025

by Bruce Kimmel, JK Black Oak Bat Project Director

In 2021, the Virginia Master Naturalist Banshee Reeks Chapter launched an acoustic bat monitoring project, starting with a pilot study at Banshee Reeks Nature Preserve. By 2022, the project had expanded to 13 sites across Loudoun County and now includes 16 active monitoring locations — among them, Loudoun Wildlife Conservancy’s JK Black Oak Wildlife Sanctuary.

Over the course of this effort, nine bat species have been consistently identified as frequent visitors to Loudoun County: Big Brown, Eastern Red, Evening, Free-tailed, Hoary, Little Brown, Northern Long-eared, Silver-haired, and Tri-colored Bats. From early on, it became clear how ecologically significant JK Black Oak is: it was the only site to record all nine of these species. Notably, it is also the only location where the federally and state endangered Northern Long-eared Bat was regularly detected throughout the year.

White-nose Syndrome (WNS), a disease caused by the fungus Pseudogymnoascus destructans, has devastated Northern Long-eared Bat populations across North America. The consistent acoustic detections of this species — alongside many others — at JK Black Oak underscore the vital importance of its habitats for regional bat conservation.

To deepen our understanding of how bats use the sanctuary and to confirm the presence of various species, Loudoun Wildlife received funding from Microsoft in collaboration with the Society for Ecological Restoration to conduct mist netting studies at JK Black Oak. In 2023, I had the opportunity to attend a mist netting training course at Mammoth Cave National Park, led by seasoned bat biologists John Chenger and Keith Christenson.

Although I had hoped to gain enough experience to lead local mist netting efforts myself, I quickly learned that acquiring the necessary permits can take years of field experience. Fortunately, my connection with Keith Christenson made it possible to establish a contract with him for this project. With over 30 years of field experience and more than 10,000 bats identified by species, Keith is one of the most respected bat biologists in the eastern U.S.

The mist netting study was permitted by the Virginia Department of Wildlife Resources and was conducted on nine nights in April, May, and July 2025, following best practices to minimize the risk of WNS transmission. These months were strategically chosen to capture both spring migrants and summer residents. Prior to selecting net locations, we deployed additional acoustic recorders near three vernal pools at JK Black Oak— Big One, LaSabre, and Fairy Shrimp — to guide net placement based on bat activity. Recordings pointed us primarily to Big One and LaSabre, where Northern Long-eared calls were most frequently detected.

Across nine nights of netting, we captured and identified 68 bats: 37 Evening, 17 Big Brown, 11 Eastern Red, and 3 Silver-haired (14 in April, 19 in May, and 35 in July). Silver-haired Bats, a migratory species, were only captured in April. In July, more than half (54 percent) of the bats caught were juveniles. One Evening Bat showed significant wing damage, possibly due to WNS, and another was released immediately due to signs of mange.

Although we did not physically capture rarer species like the Northern Long-eared or Little Brown Bats, closer inspection of the acoustic recordings revealed that Northern Long-eared Bats were indeed present but between 2 am and 5 am, after the nets had been closed. Little Brown Bats were not acoustically detected on the netting nights.

Despite dry conditions in the vernal pools, the study provided valuable data. It showed that Evening Bats are the most common species at JK Black Oak and reaffirmed the sanctuary’s role as a stopover for migrating Silver-haired Bats. The placement of acoustic recorders near Big One and LaSabre also revealed that Northern Long-eared Bats frequent wooded areas not picked up by our acoustic recorder in the field.

There were even a few lighthearted moments, such as getting stuck in the mud at LaSabre, exchanging bat stories, releasing a flying squirrel from a net, and watching one of the biologists take an unexpected plunge into the pool.

As we continue to monitor JK Black Oak, we’re excited to see what future seasons will reveal about the county’s most ecologically important bat habitat.