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Crows return after West Nile die-off

Crows return after West Nile die-off


The crows are back.

The big black birds, known for their evil looks and loud cawing, were devastated by West Nile virus a dozen years ago, and the population remained depressed until late in the last decade.

Now, they seem to be beating the bug.

The Audubon Society’s Christmas Bird Count indicated that the bird population may be back to pre-virus levels in Illinois, and recovering part of its numbers in Missouri.

“They’re almost back to where they were 10 years ago,” said Robert Russell, a biologist at the U.S. Fish and Wildlife Service, referring to the Midwest. “Our crows are pretty much back to normal.”

Whether that’s good or bad depends on how one views a bird blamed for eating farmers’ corn, known for munching on roadkill and cursed for their cacophonous racket of cawing that wakes people up.

“I like them in the distance, but I don’t like them on Saturday morning,” Russell said.

Among all birds, crows were perhaps the most susceptible to West Nile. It’s a virus spread by mosquitoes, both to birds and people.

Most infected people shrug it off. About 80 percent have no symptoms. Most of the rest have mild cases with fever, aches, nausea or a skin rash. Only one in 150 people becomes seriously ill.

As with people, most bird species also show little effect. But West Nile is murder on crows. The death rate for infected crows was 99 percent when the disease first appeared in 1999.

As a result, infected crows are little danger to people. “Crows don’t spread it; they die too fast,” said Kevin McGowan, an ornithologist at Cornell University and an expert in crows.

Great horned owls, red-tailed hawks and some types of jays are also highly susceptible, and suffered in the epidemic.


It’s hard to count birds. They fly around and hide in the leaves, frustrating the Audubon census takers. Crows are particularly hard because they gather in large roosts. A birdwatcher near a roost will count many crows, potentially distorting the census.

The Audubon Society judges the bird numbers by how many its census parties spot in an hour. In 1999, when the disease arrived on the East Coast, watchers in Illinois were averaging 96 crows an hour. By 2007, it was down to 30. But by 2011, it was up to 104.

In Missouri, where the forested terrain is less hospitable for the birds, the hourly count went from 8 per hour in 1999 to 3 in 2008. It hit 6 per hour in 2010, before falling to 5 in 2011. The figures for Christmas 2012 are still being compiled.

In St. Louis, homeowners found many dead crows lying in their yards a decade ago, but the biggest kills were in Illinois, Indiana and Ohio.

No one knows why the crows seem to be returning now. West Nile is still with us, although at reduced rates. There were 21 human cases in Missouri last year, compared with 168 a decade earlier.

After the worst years for bird kills, scientists sampled birds to see if they were developing antibodies to the virus. “We didn’t find any,” said McGowan, the Cornell crow expert.

The answer might lie in a sort of high-speed evolution. The crows that survived have the most natural resistance to the disease, and they’re passing it on to their progeny, said Geoff LeBaron, the ornithologist in charge of the Audubon bird count.

Few people are crowing about the return of crows. The birds have an image problem. A flock of jays is called a “party,” a group of sparrows is a “host.” But a flock of crows is a “murder.”

“We got the varmint mentality from Europe,” McGowan said. “There are no vultures in Europe. Crows are black and they’re scavengers. They were always the harbingers of destruction and death. They don’t even sing pretty.”

McGowan thinks they get a bad rap. Take their role in agriculture.

Scarecrows are testament to farmers’ view of the birds, which they blame for eating crop seeds and other sins. But McGowan notes a study that found that crows also eat corn borers, a pest to the corn crop.

“Fields with crows have higher production,” he said.

Their other feeding habits don’t help their reputation. “They’ll eat anything, practically, but green vegetation,” said Cornelius Alwood of the Audubon Society’s St. Louis Chapter, who co-authored a book on St. Louis birds. “Roadkill is one of their favorite foods. They will go into other birds’ nests and eat the eggs.”

But they’re protective of their own young. “The crows will mob all the raptors,” Alwood said. “The crows will circle, then dive to attack the owls and the hawks.”

Crows are good family birds. They often mate for life, and big extended families roost together.

They are also quite smart. In New Caledonia, a South Pacific Island, crows even make tools. They take twigs and bend a little hook at the end, which they use to pull food out of tight places.

The birds can recognize individual humans by face. McGowan feeds unsalted peanuts to the crows in his backyard, and they’ve come to know him. “I was chased down the street by a family of them today.”

They even recognize his car, following it down the street and flying in front of the windshield to get his attention, in hopes he’ll toss out some nuts.


Of course, crows like people for reasons beyond peanuts. We’ve created a crow-friendly environment.

“They like open fields, but they roost in stands of trees to breed,” Alwood said. In the east, humans cut down forests to create farm fields. In the western prairies, we planted trees.

Now, the crows want to get even closer to us. They’re becoming more of an urban bird.

“They never used to be super urban creatures because every kid had a BB gun,” said Russell, the government biologist. “Now when we see a kid with a BB gun they call the SWAT squad.”

They may also be drawn to city lights, which help them spot owls at night, LeBaron said.

That means more St. Louisans subject to one of crows’ least popular traits — noise.

Before the die-off, roosts of 25,000 to 35,000 crows were reported, swarming in the tree groves.

“I remember 20 years ago in the Central West End there were thousands of them, and what a racket. They drove you nuts,” Alwood said.

But Alwood is still fond of crows. He remembers one from his childhood, part of which was spent in the old St. Vincent orphanage in Normandy. The custodian there had trained a pet crow, who would ride around on a dog’s back. He trained the bird to repeat a single word, “Nevermore.”

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