The caw of the wild: Crows take command in Denver during annual incursion
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DENVER — “History doesn’t repeat itself, but it often rhymes,” Mark Twain famously said.
In Denver, it often caws.
Every year since 2022, local journalists reported on an annual phenomenon: thousands of crows laying claim to entire blocks of downtown Denver, defecating in such staggering amounts that whole sidewalks have the appearance of a haphazard white-wash.
First it was Denverite, then Westword and, most recently, the Denver Gazette. Allow Rocky Mountain PBS to join this media murder.
Our office at the Buell Public Media Center is just a few blocks away from the 1700 block of Arapahoe Street, where the crows most visibly congregate each night. Bundled-up commuters at the nearby 17th and Larimer RTD stop look to the sky as they wait for their bus, aiming their cell phone cameras at the fluttering mass of corvids in the twilight.
Crows have descended to Colorado’s Front Range en masse for generations, evidence of the famously intelligent birds’ adaptation to changing urban landscapes. But some experts worry that the warming climate will change these annual gatherings.
Kieran Fish is the youth environmental educator with Denver Audubon, a local nonprofit focused on bird conservation.
“When the birds are migrating into Denver, they're coming from areas to the north of us because obviously, harsh winter conditions make it hard for them to find food,” Fish said.
With a warming climate, though, crows may not need to travel as far south in the future — something that is already happening with Canada geese.
“It might mean less crows migrating down here into Denver,” Fish said. “It might mean less crows migrating in general.”
Garth Spellman, an ornithologist at the Denver Museum of Nature and Science, said that in addition to crows flying down from Canada, Denver also welcomes crows migrating from Colorado’s high country. These two groups congregate with Denver’s “resident crows” — i.e., the crows who stay in the city year-round — making for more noticeable murders.
“Crows, like many other species, they gather in those large numbers at roosting sites at night,” Spellman said. “It's not just social. A lot of it is for safety. And then also they will gather together because body heat can help them make it through those cold evenings.”
Around 5:00 p.m. on Jan. 15, as soon as the sun began to lower behind the mountains, a wall of crows descended from the roofs of the Granite Tower and the Ritz-Carlton and occupied the trees on Arapahoe Street, an example of the roosting sites Spellman mentioned.
The local fascination with crows extends beyond Denver’s skyward-looking journalists. An online map from the Cornell Lab of Ornithology’s popular eBird app shows a hot spot of American Crow sightings along Colorado’s Front Range.
“They're what we call ‘urban exploiters,’” Fish said of crows. “They're animals that kind of thrive on human settlement. And usually, you know, they're eating our trash and things like that. But I think that, in a way, that kind of speaks to their intelligence as foragers, as problem solvers, as social animals — that they can live in these urban environments so effectively.”
The crows on 17th Street are unfazed by Denver’s clamorous soundscape — sirens, barking dogs and car horns were not disruptive enough to make them find another roosting location.
What could make the crows disperse? That’s a question Colorado’s game and fish commissioner Roland G. Parvin tried to answer almost a century ago.
The Rocky Mountain News published an article in March of 1936 with the headline “War to Death on Marauding Crows Declared by Parvin When Salt Fails.”
The piece detailed Parvin’s trip to an area near Fort Lupton to “do battle with thousands of marauding crows.” Farmers had complained about the crows damaging crops, and Parvin’s plan was to fight the birds with salt — which can be harmful to birds — but he reportedly failed because the crows were perched in cottonwood trees.
“The crows Parvin is interested in gather in a grove of trees each night, flying from miles around,” the article said. Some things never change, apparently.
The next day, the Rocky published a follow-up with the headline, “Visibly Shaken, Our Mr. Parvin Will Let Boulder Vets Eliminate ‘Pet’ Crows.”
“There were too many of them,” he said, “but the war is not over really. There are others who will carry on.”
The “others” were a group of Boulder VFW members who on Saturday, March 14, 1936, shot more than 800 crows near Fort Lupton — and then ate them. “The flavor is superior to that of all game birds with the exception of quail,” one of the men said.
The crows who survived the massacre may have remembered their attackers. A study from University of Washington professor John Marzluff, who has studied crows for decades, found that crows can recognize specific faces they deem threatening and communicate these threats to their offspring.
More recent studies have found that crows can have subjective experiences, throwing a “bird-shaped wrench into our understanding of evolution.”
But today, climate change poses a more prominent threat to crows than armed-to-the-teeth Boulderites. Rising temperatures, as Fish noted, are changing migration patterns and where birds live. Global warming is also correlated to the abundance of mosquitoes and the disease they carry, like West Nile Virus, which is especially fatal for crows.
There is some good news. Crows and other corvids, like ravens, jays and magpies, play an important role in reforestation. The birds scatter seeds as part of their food-storage strategy, and many of these seeds go uneaten. The uneaten seeds can grow into trees and other vegetation.
In his book “A Natural History of the Future,” biologist Rob Dunn made the case for crows as a model from climate resilience.
“When crows use their inventive intelligence to deal with novel conditions, they do so by finding new ways to find foods and by eating novel foods. In essence, they diversify their diet so that even if a species they rely on becomes rare, some other species might be common,” Dunn writes. “We, too, can take advantage of nature’s diversity, whether in our farm fields or even on our bodies, in order to buffer our risk.”
Video: NATURE | PBS
Type of story: News
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