Mark Vukovich never imagined the discovery he'd make when he visited a stand of timber in Hardin County.
Vukovich, a wildlife biologist for the Shawnee National Forest, visited what the Forest Service calls the "Lee Mine" area, to survey two stands of timber that had been thinned in 2018 and 2019.
While there, Vukovich, an avid birder for more than 20 years, realized he was hearing several bird calls he didn't immediately recognize.
Using a bird identification app on his cellphone, he played several bird songs and calls until he made a match: they were red crossbills, a species of finch that normally lives in the Pacific Northwest, Canada and Alaska.
He was surprised, but not shocked.
"This year is considered a major irruption year, and some finch experts predicted that we might see species that otherwise wouldn't be in this part of the country," Vukovich said.
An irruption is a biological event in a species where an overabundance of food leads to higher reproduction. Then, when food in a species' normal habitat is depleted, that species sets out en masse to find food elsewhere. Besides red crossbills, this winter's finch irruption has brought species such as evening grosbeaks, and common redpolls to southern Illinois.
Vukovich said he was elated with the discovery.
"I started recording their calls, taking video and photos," he said. "I knew this could be huge, and felt like a 14-year-old kid again."
In all, he counted 10 individual red crossbills, but felt that his count was conservative. The birds often stay near the tops of the mature pines in the stand and move frequently, making counting them a challenge.
He returned to the location, next to Hardin County's Waters Cemetery, four days later and visited another nearby portion of pines that also had been thinned at about the same time. He found nine birds at the original site and another 30 at the second pine stand. Again, he said, he felt his estimate at both locations was conservative.
A third trip to both sites on Jan. 2, accompanied by his wife, revealed at least 50 birds at both locations, which total about 130 acres of short-leaf pines.
In the meantime, Vukovich contacted an expert at Cornell University to determine what type of red crossbills were feasting on the pine cones. Red crossbills are divided by ornithologists into 10 different types, each of which has its own distinct vocalization.
Vukovich submitted recordings to Matthew Young at Cornell, who identified both Type 10, or Sitka spruce, and Type 4, or Douglas fir, red crossbills.
The Douglas fir red crossbills normally stay in the Pacific Northwest, occasionally irrupting to other western states and sometimes the northeast U.S. when food gets scarce. The Sitka spruce red crossbills also inhabit the Pacific Northwest in northern California up to central Oregon and normally travel to the same parts of the country during an irruption year.
"I was stunned how far this species has traveled to visit this part of the country, and the fact they've remained this long also is highly unusual," Vukovich said.
Red crossbills often descend upon stands of conifers for no more than a couple of days before moving elsewhere. The birds Vukovich discovered were confirmed to still be in the area by other birders on Jan. 11.
"The birds I've seen were in the pines on the Forest Service property, but I observed some of them flying toward the direction of other private property nearby. I suspect they fly in and out of areas quite a bit," Vukovich said.
He also said the observations provide an interesting insight into selective timber harvesting on Shawnee National Forest properties.
"Often, when the Forest Service harvests timber, we get criticized by people and they often reference possible harm to wildlife," Vukovich said. "But this area, about a year removed from timber harvest, shows high numbers of many species of birds besides these rare visitors."
