On most winter nights, 30,000 to 40,000 crows fill Hill District trees overlooking Bigelow Boulevard. It's a loud, dramatic spectacle that obviously brings to mind Alfred Hitchcock's 1963 movie, "The Birds."
The daily crow-roosting in winter months occurs at three sites in the region, and possibly others, including in the Hill District; from Bridgeport to Martins Ferry, Ohio, near Wheeling Island, W.Va.; and near California University of Pennsylvania along the Monongahela River, Washington County.
But it's nature not horror -- something to behold not fear -- said Kevin J. McGowan, an ornithologist with the Cornell Lab of Ornithology. And let's be clear: Those bad guys in "The Birds" were seagulls.
Crows flock to Bigelow Boulevard trees each winter
Each winter, as many as 40,000 crows gather in the trees along Bigelow Boulevard in the Hill District. (Video by Rebecca Droke; 2/16/2014)
"I think this association is unfortunate," the doctor of biology said about comparisons with the movie. "Such roosts are something to be marveled at."
Ornithologists agree that crows roost by the thousands to provide safety in numbers, preferring areas surrounded by light to help them spot such predators as the great horned owl. Single trees can hold up to 3,000 crows, each bird weighing a pound. Roosting sites near rivers provide heat with water temperatures typically warmer than air temperatures.
But roosting also is social behavior that Mr. McGowan compares to people heading to a ballgame or resort. They might not interact much but have a common purpose.
Only in recent decades have crows begun roosting inside city limits. Small cities now are preferred locations. The question is whether the cities grew to envelop the roosting sites, or the crows realized urban advantages -- river heat, lots of light and fewer natural predators -- over isolated woods, Mr. McGowan said.
Roosts typically draw tens of thousands of birds. One in Oklahoma drew up to 2 million with others documented to have 100,000 or more, which was the estimate decades ago for the roosting site near Wheeling.
"There's a host of things that come into play," Mr. McGowan said. "But generally when animals gather together in large numbers, it has something to do with predation, food gathering and there may be other reasons which are tough to pin down. Crows just seem to like to be with other crows."
Once March arrives, the migratory crows depart to New York or farther north to feed, breed and raise their young.
A boulevard view
Last week, against an orange sunset, crows begin sprinkling into ridge-top trees in the Hill District. Within minutes the sky was peppered with crows, with a black stream of birds arriving from the southwest, although they usually come from all directions. Tree branches behind Pittsburgh Miller PreK-5 on Bedford Avenue soon were filled.
"These guys should be put in the movies," said Leroy Dillard, who lives on Arcena Street in the Hill District.
Even though the crows have roosted there for 20 years, he still wondered aloud whether they might attack a person -- or a bald head. Mr. McGowan said they get aggressive only when defending their nest. But their loud, almost angry-toned chorus of caws at dusk does resemble a horror-show soundtrack.
"It amazes adults when they see it for the first time," said Mr. Dillard, who teaches at Clayton Academy on the North Side. "Their jaws drop. They don't know if a storm is coming or something bad is happening in Pittsburgh. It puts them in heavy shock. And the noise -- that really gets them going."
In recent years, a new species of crow has joined what has historically been all American crows in Pittsburgh. The fish crow, once exclusive to the Atlantic seaboard, has found its away over the Laurel Mountains. The smaller, more upright crow with a vocalizations of "uh-uh" rather than "caw-caw," now makes up 1 percent of local crows, said Bob Mulvihill, an ornithologist with the National Aviary of Pittsburgh. He also noted that arctic and other gulls have made a rare appearance at the Point along the Allegheny River this year because the Great Lakes are icing over. (See accompanying story on this page.)
Crows are highly intelligent birds with cognitive abilities approaching that of apes, including an ability to count and solve problems. They have no trouble finding food they've hidden long ago.
"They definitely can put 1 and 1 and 1 together and get 3," said Mr. McGowan, a crow specialist.
Their numbers dwindled in 1900 after they were hunted to reduce their impact on corn crops. That led to creation of the scarecrow. Crows were headed toward extinction. But the Migratory Bird Treaty Act of 1918, extended in 1972, provides protection, unless their population soars in an area. Their population nationwide continues edging up although the West Nile virus did cut back the numbers, especially in Ohio, Indiana and Illinois, Mr. McGowan said.
Their quirky intelligence, crazy behaviors and loud cawing, coupled with their pitch-black feathers, have led many cultures to consider crows symbols of death.
The result is rock bands (Crow, Counting Crows and even The Black Crowes), a bourbon whiskey (Old Crow named after its creator with that surname) and several movies with "crow" in its title ("The Crow," "The Crow: City of Angels," and "Murder of Crows"). While ornithologists refer to a group of crows as a flock, literature and poetry prefer the more chilling description: A murder of crows.
But Mr. McGowan said that reputation is undeserved. Crows are more like humans than demons.
"They have family values," he said. "They have neighborhoods and have morals. They are very much like us. They would rather eat Cheetos than dog food, and they love french fries, and we have photos of them drinking out of beer cans and eating pizza, just like we do."
They also are monogamous, finding another mate only when their partner dies or can't reproduce. Younger crows return for years to help their parents raise the young. Crows are "party animals" who enjoy being among other crows, Mr. McGowan said.
Decades ago, about 100,000 crows would gather along the Ohio River north of Wheeling, but that number has dwindled in recent years. They still gather before nightfall in the high ridge tops before heading to trees, on this occasion, in Bridgeport near Wheeling Island. Sometimes they venture a half mile north to Martins Ferry.
Allen Marangoni, 65, of Martins Ferry, a physical therapy professor at Wheeling Jesuit University, said he enjoys the nightly pageantry of crows arriving to roost, especially when he has the right music playing.
"I think what I really like about it is that it's an unexplained event in nature," he said. "We feel we're so bright but let humans try coordinating 50,000 individuals coming in each night in organized fashion. Think of the difficulty when we try doing that with people -- the effort to bring that many people to a ballgame. But the birds do it. They know what to do and how to do it, all in 3-D from the sky to tree limbs."
And most people don't even realize it's happening.
No landing zone
In recent years, thousands of crows have tried to create a roost along the Monongahela River in trees on the California University campus. Officials, citing health and safety risks, hired a company to disperse the crows by spraying roosting areas with grape extract, an irritant to crows. The method sent them on their way, said Christine Kindl, university spokeswoman
"They do present a lot of waste," she said. "We're hoping we taught them, with abatement efforts, not to roost here. If the extract had not worked, they would have used laser lights and noise to disperse the murder."
The crows first posed problems in 2010, but weren't as numerous during relatively warmer winters in 2011 and 2012. "Their travels seem to have to do with the weather," she said.
The university's success, however, became California Borough's challenge.
Just weeks ago, the borough also called in professionals who dispersed the crows with the same extract. "But everybody worked together and we were able to have a company come in and enact a solution," said Timothy Buchanan, California Borough manager. "It was very simple and safe."
No one knows where the crows went. Mr. McGowan said they might find another roosting site along the Mon or travel to other roosts in the region.
Caws and effect
Mr. Dillard, the Hill District resident, said he's amazed at what happens around, and sometimes on, his house in a city neighborhood. For one thing, the crows have attracted feral cats that hunt the crows.
"These are strong, big-headed cats that scare you," he said. "With these cats, you can stomp your feet and clap your hands and they look at you as if to say, 'OK, what's next?' They don't care."
But his focus is the same crow mystery biologists are working to explain -- why thousands of birds head to a particular location, October to March.
"Seriously, it makes me wonder how they gather up so multi, and never run into each other, and have their own signals -- how they team up to be together and know when it's time to settle down and rest," Mr. Dillard said.
"It's amazing to live in the city and see this stuff."
David Templeton: email@example.com or 412-263-1578.