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Sound Research at Crossroads at Big Creek: Wildlife Inventory Goes High Tech

Ten distinct types of habitat attract a diversity of insects, birds, mammals, amphibians, reptiles and fish to the 120-acre Crossroads at Big Creek, but it’s impossible for staff members and volunteers to see, find or count all of the species that live or pass through the site.

That will soon change.

As spring arrived, Gary S. Casper and fellow scientists set up electronic equipment, including acoustic monitors, to capture signs and sounds of the birds, bats, frogs and other wildlife at the preserve on Sturgeon Bay’s east side. 

Casper is a University of Wisconsin-Milwaukee field-station scientist and Great Lakes-region wildlife expert. He appeared on Zoom on March 19 during an hour-long Crossroads program for an audience of Crossroads supporters and others who are concerned about habitats in Door County. Casper said it was his first visit to the preserve, which he called a “wonderful place.” 

Coggin Heeringa – Crossroads’ longtime director and its current program director and naturalist – said that for the next four years, Crossroads staff will remove cards intermittently from the sound-detecting equipment to upload data for Casper and his crew to interpret. Initially, the devices will be set to frequencies in a range to detect birds and frogs that computers can identify. Later, sound equipment will be set up to detect the higher-pitched sounds that bats emit. 

The Crossroads at Big Creek restoration team watches as scientist Gary Casper, a UW-Milwaukee field-research leader and Great Lakes-area amphibian expert, installs electronic acoustic monitors to help with accurate counts of birds, frogs and bats, day and night. Submitted.

To establish baseline data at the beginning of the study, Crossroads will have “Bio-Blitz” days when naturalists and volunteers will identify dragonflies and damselflies, while also staying on the lookout for other species. 

The Crossroads at Big Creek Learning Center and Nature Preserve already has more than 20 years’ worth of anecdotal records on wildlife, but Heeringa hopes the sound-detecting devices will find many more species, such as animals that go unseen at night.

Casper said many groups work to preserve, expand or create habitat, with the goal of attracting wildlife over time. The if-you-build-it-they-will-come method tends to work for birds, roaming mammals and some fish, but those efforts often neglect the needs of tiny native fish and certain reptiles and amphibians. 

Casper wants to identify all of the animals currently living in or recently verified in the study area. 

“What are the species, and which should we care about?” he asked. 

Casper and his crew members spent four years collecting copious amounts of data and then monitoring and inventorying the wildlife north and northwest of Milwaukee in the Milwaukee River basin. Their research and new database are helping to steer millions of dollars in cleanup and restoration efforts by two counties and the Environmental Protection Agency.

Their methodology included a year spent data-mining for all reports pertaining to wildlife in their research location. After compiling data, they donned boots and ventured into the urban wild, collecting specimens, taking photos, setting fish traps and installing motion-activated cameras and sound-monitoring equipment.

They identified two bat species – the evening bat and tri-colored bat – that had not previously been documented in Wisconsin and found that some bat species listed as imperiled were plentiful in the Milwaukee estuary. They also discovered rarities such as the star-nose mole at the southern limit of its range, plus some species that were thought to be common, such as the fox squirrel, that were not common at all. 

In the Milwaukee estuary, where no one else was “bothering to look” for species, Casper’s group found the digger crayfish, which had not previously been documented there; eight “impaired” species of mussels; and 54 fish species of local concern ranging from types of chubsucker and killifish to the elsewhere-common black crappie. 

“This was a four-year phase, and one that’s just starting at Crossroads,” Casper said.

At Crossroads, Casper’s group members hope to make similar discoveries. They will also identify species that have been effectively extirpated, or those that could not be reintroduced and survive strictly within the 120-acre Crossroads at Big Creek location, such as wolves and bears.

The researchers discovered that coyotes had become common in the Milwaukee area – a good sign for the estuary.

“They were the only predator on grazers,” Casper said. “Rabbits and deer can have really adverse effects on the ground-level plant community.”

Crossroads at Big Creek has been working for years to undo a century of agricultural practices that altered the natural landscape. In addition to making those corrections, it’s involved in an all-out war against invasive nonnative species such as buckthorn and canary grass. The property has come a long way back toward a natural state, and the four-year study will further assist its revival. 

Crossroads can also use Casper’s findings to further improve the 80-page Environmental Restoration Plan completed this winter by Dan Collins and Nancy Aten of Landscapes of Place.

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