Red crossbills, bald eagles and other unexpected birds have been spotted in Chicago this winter

After walking the grounds of the Morton Arboretum for hours on a December morning, John Leonard and fellow birders were preparing to go to lunch when they encountered a rare sight: a flock of 17 red crossbills flying overhead and landing on some pine trees.

The retired neuroscience professor has been an active birder since he was 12 and has participated for almost four decades in the arboretum's annual Christmastime bird count. "It's always kind of like a treasure hunt."

Leonard said red crossbills are known for their irregular migratory tendencies: "They come in in waves and then they're gone, and you don't know if you're going to get a chance. They're not a common bird at all."

These bird "irruptions"—sudden, sweeping visits from northern species—often occur because of a fluctuating food supply.

But experts agree that recent sightings of birds not often found in the Chicago area, from dozens of red crossbills spotted in big groups in city parks to a pair of long-eared owls and a lone bald eagle, can be caused by distinct factors.

"When we do have these years, they're—generally speaking—pretty unexpected," said Edward Warden, president of the Chicago Ornithological Society.

"And oftentimes the answers for why even every one of these bird species irrupts is different and unique to that species. So just because it's an irruption year for this species doesn't mean it is for another. Or they might irrupt together at the same time but for completely separate reasons."

"It's kind of like climate change, where it's hard to say, 'This specific thing is exactly what's responsible for how things are unfolding,'" he said.

But not all of the unusual bird sightings in the area can be attributed to these large and irregular southward migrations.

In the South Loop, it had been more than a decade since the appearance of seven long-eared owls caused a ruckus in the neighborhood. Last month a pair returned.

Bald eagles are native to most of North America, but it can be rare to see them within city limits—like the one spotted two weeks ago flying over the North Branch of the Chicago River.

"I think each of these cases is a little different, what's going on," said Doug Stotz, a senior conservation ecologist at the Field Museum's Keller Science Action Center.

Long-eared owls often visit the Chicago region for the season, but they only do so once in a while in large numbers.

Meanwhile, the bald eagle's presence represents to birders a comeback that has been years in the making, and which has become more noticeable as green and blue spaces in urban areas are restored.

"Eagles have increased dramatically in Illinois, both the breeding population and the wintering population," Stotz said. "Illinois now has the biggest wintering population of eagles in the lower 48, and basically the lion's share of that is the Illinois River and Mississippi River."

Driven by food

The red crossbills, native to Canada and the Rocky Mountains, use their oddly shaped bills—the upper tip crosses over the bottom one, hence the name—to feed on seeds from conifer cones. This characteristic means the little red birds have adapted evolutionarily to specifically eat from evergreen tree cones, Warden said.

The reasons behind an irruption are often many and complex, but any big migrations of red crossbills are mostly driven by food, he said. When conifer crops are poor or insufficient, they will search elsewhere for sustenance.

"They will migrate south and show up in unexpected places, and Illinois is one of those unexpected places," Stotz said. They tend to prefer forest preserves and cemeteries where pine trees and other evergreens abound.

When conifers produce plentiful cones, red crossbill populations will grow due to the overabundance of food. But with more well-fed birds, competition increases, driving some to other places where they don't have to fight for cones.

There are, however, other circumstances that can deplete food sources, such as the wildfires that struck Canada last summer.

"Fire will burn up, literally burn up food resources, like your pine cone trees, and they have to move in response to those kinds of conditions," Warden said. "We see this happen too, with a certain insect species that will also decimate stands of trees. The pine bark beetle is a notorious one. And if they have a really good year for the beetle, they kill a lot more trees and so there's a lot less food to go around."

The red crossbill irruption in Chicagoland will likely peak in February, experts say, but they could potentially be seen until April. Warden has yet to spot one this year.

"It is driving me up the wall," he said. "It's one of those things where I just haven't been in the right place at the right time to catch them, but they're around and I'm still looking. I haven't given up hope for this winter."

Roosting in the South Loop

At lunchtime on a regular workday 16 years ago, dozens of awestruck pedestrians crowded the sidewalk of a South Loop park. They were itching to catch a glimpse of seven long-eared owls roosting in a grove of pine trees.

The hubbub from the big, chatty group drew more attention from passing cars and cyclists. Eventually, the Chicago Park District set up a fence so people wouldn't get too close while viewing the owls. District signage also asked visitors not to disturb wildlife.

The recent sighting of a pair in the same neighborhood—the first one recorded in 14 years in that area—could reignite similar concerns for the well-being of the wintering birds, according to experts. But so far, they seem undisturbed.

"People are being much more circumspect about talking about them," Stotz said. "Those got reported and so far have hung on."

City officials are also paying close attention as wintering birds roost in local parks.

"We have fencing in place in other highly frequented birding locations for the protection of the habitat and wildlife," a Chicago Park District spokesperson said in a recent email to the Tribune. "Currently, there is no fencing in the area but the District will continue to work with experts, including the U.S. Fish and Wildlife Service and Illinois Department of Natural Resources, to take action if it is recommended in the future."

Though long-eared owls—with their unique, long ear tufts that point straight up like exclamation marks—do travel to Illinois and Chicago from northern climates in the wintertime, it's hard to say when there are enough of them to call it an irruption, Warden said. They are incredibly hard to spot because of their cryptic coloration, which allows the birds to easily camouflage with foliage.

"I mean, even when the trees have no leaves on them, they look like bark, like a branch on the tree," he said.

Because they blend into their surroundings so well, passersby and experienced birders alike might miss them. They are easier to find when they are in larger groups or if specific individuals are uncharacteristically carefree.

"It's a personality thing," Warden said. "Most of these birds tend to be very sneaky and secretive and not about that whole human thing. And then there are others, like the ones in South Loop … their temperament and personality is one where they really couldn't care less what people around them are doing or saying and hanging out. And as long as they're not being directly harassed, they just chill."

According to local birders, the group of long-eared owls that drew citywide attention in early 2008 stayed in the area until the end of February. They had been regular visitors in the vicinity since the winter of 2005–06 and were seen in smaller numbers in later winters until 2009–10. However, long-eared owls continued flocking to other Chicago neighborhoods, notably in 2017.

Back in 2008, birders and residents had reported that the long-eared owls in the South Loop area would frequently fly to and from the west, likely feeding in a weedy, open habitat east of the Chicago River, south of Roosevelt Road and west of Clark Street. It was the single biggest parcel of undeveloped real estate downtown.

Now, that land is part of The 78, a 62-acre site that will become the newest addition to the city's 77 community areas. Once a rail yard from the early 1900s to the 1970s, it remained a vacant lot for decades until infrastructure work for the megadevelopment began four years ago.

According to developers, The 78 will have a 7-acre park and more than 40% of the neighborhood will be green or public open space, "lush landscapes" of "fragrant gardens" and "wide lawns." Plans also include skyscrapers as tall as 950 feet.

"Specifically for long-eared owls, that probably isn't going to be too big of an impact," Warden said. "This is a bird that likes close, quiet, secluded, cozy trees, and that area has always been mostly very kind of grassy, weedy."

That's not to say the development won't have impacts on other urban animals and birds, he noted. He has often seen kestrels, a type of falcon and grassland predator, hunting in the area.

"It is a huge space. This isn't like your neighborhood corner, a lot sitting vacant; this is several acres … people have been seeing all kinds of wildlife and birds in there for years," Warden said. "Who knows what kind of a larger impact that's going to have on all these species that were using the area?"

'Spreading their wings'

The bald eagle, the country's national bird, can be found across Alaska and all of the contiguous United States. On the Southeast Side of Chicago, they breed and nest near Lake Calumet and the Calumet River and in Big Marsh Park. But they are seldom seen close to the heart of the city.

"They will show up from time to time," Stotz said, "but it's a relatively rare sight in the city proper. We just don't have great water for them."

Because the river typically freezes over during the colder months in Chicago, bald eagles are unable to find open water where they can hunt for fish.

"When the waters open, they can go along the North Branch and they'll find food," he said. "But in a normal winter, the water there would be frozen solid and there wouldn't be anything for them."

While bald eagles have been seen flying through and near the river for years, this time seems to be different. It's the first time in decades that one has stayed in the area, according to Warden.

Still, no nesting activity has been confirmed. If the bald eagle had a nest by the river, it would be unmistakable: It wouldn't be a random pile of sticks but "massive," and there would be a second eagle present.

Indeed, Warden said "it's been a minute" since an eagle's nest was documented in the city—well over a decade. In 2012, the discovery of the first bald eagle nest in the city since the 1880s frustrated plans for a Chicago Police Department outdoor shooting range on the Southeast Side.

Like other bird experts and nature lovers, Warden said he believes the bald eagle's persistent presence on the North Branch is evidence that the river "has come such a long way."

"Clearly, this bird wouldn't be hanging out if it didn't have food and resources available that are found in the river," he said. "So that's an amazing thing."

Generally, recent years have brought an uptick in bald eagle sightings in Chicago.

"The cool thing about this is that it really is showing that they are spreading their wings—no pun intended—and really stretching across the city," Warden said. "I've been saying for years that it's only a matter of time before bald eagles become a common sighting within the city limits."

From the color of an eagle's feathering, experts can discern its age, so they know that it is not just one or two individuals but rather generations of birds that are hanging out, passing through and returning to Chicago.

"All these birds clearly indicate that Chicago is the farthest thing from dead and quiet during the winter. There's all kinds of life happening," Warden said. "But then, also, it really is a testament to the wild diversity that you can find in this space. All of these different living things are here for different reasons, but they're all still here, converged in this space all the same."

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