With a whoosh, Clive, a 7-month-old Harris's hawk, spreads his wings and takes flight over the wet streets of downtown Portland. The skies are dark and cloudy on a chilly January evening, but Clive's keen eyes dart from treetop to treetop, scanning.

A few blocks away, Mars, an older hawk, is also patrolling the skies and, a few blocks from that, a third bird is searching the streets.

They're all looking for one thing: crows.

These hawks are not here of their own volition. They were loosed on the crows of downtown by Kort Clayton, owner of Integrated Avian Solutions, a Portland-based company that uses hawks and other raptors to shoo away problem birds from wineries, dumps and, in this case, business districts.

Clayton was called in after years of fruitless efforts at driving out the bothersome birds. Crows were eating the insulation from building walls. They created such a roar that hotel guests were jolted awake at early hours. Most notably, they left busy sidewalks slickened with poop.

The problem

Sheri Scali, senior property manager at a large building near the Keller Auditorium on the south end of downtown, heard them before she saw them. It was early January and as she was heading into work before dawn, she was greeted by the busy cackles of roosting birds.

They hadn't been there the day before and they were loud, but she didn't give the flock much thought until the sun came up. Under the light of day, Scali witnessed the mess a large group of crows is capable of creating overnight.

"When we looked down from above, it looked like it had snowed," she said.

During the day, crows spread out across the Pacific Northwest, scavenging what they can from sites urban and rural alike. But once the sun heads toward the horizon, they seek warmth and safety in numbers, gathering in flocks of up to 10,000 birds and descending on the trees and parks and rooftops of downtown Portland, Clayton said.

During the great snowstorm of early 2017, a Portland Police criminalist snapped a picture of a flock gathered next to headquarters. The crows were so numerous, and contrasted so starkly against the fresh blanket of snow, that the trees looked like mashed potatoes covered in pepper.

Forensic Evidence Division Criminalist Walker Berg took this amazing photo from the 12th floor of the Justice Center. We... Posted by Portland Police Bureau on Thursday, January 12, 2017

Their ubiquity, at least during winter months, makes them hard to ignore.

When flocks, known ominously as "murders," gather in these numbers, a cacophonous maelstrom announces their evening arrival. Crows are deft communicators and they waste no time telling each other about the exploits of the day. They squawk and bray and bleet from the treetops, drowning out the sounds of the city below.

The din is bothersome, but mostly harmless unless you're trying to sleep. The problems created by that many birds, fresh back from a day of feeding, is feculent. Or to put it more simply, it's their poop.

The roosting birds, drawn to the downtown core by warmth and an abundance of food sources, started to become a problem about four years ago when everything beneath their preferred trees quickly took on a sheen of avian excrement. Trees, cars, sculptures and downtown pedestrians all became targets of the droppings.

In 2014, more than 30 crows were found dead in Portland's urban core. An investigation by the Portland Audubon Society found the birds had been poisoned. Last week, witnesses in Northeast Portland reported seeing some crows "falling from the sky," while others were found seizing on the ground.

An investigation into the most recent spate of crow deaths is ongoing, but appears to be consistent with poisoning, said Bob Sallinger, conservation director with the Audubon Society.

When the crows began to congregate in such large numbers, complaints poured into Downtown Clean & Safe, a program that works in partnership with the city and the Portland Business Alliance to provide cleaning and security services to the downtown area.

Working with Central City Concern, the city hired crews to pressure wash the streets of the crow-created mess, but it was a sisyphean effort.

"We would pressure wash all night," said Lynnae Berg, executive director of Downtown Clean & Safe. "And then the crows would wake up and it would look like we had done nothing."

As it became clear they couldn't beat the problem with pressure washing alone, they called in a device called the "Poopmaster 6000," a motorized brick-scrubbing cart that resembles a Zamboni. The Poopmaster worked great on the ground, but did nothing for the bird poop that shellacked benches and newspaper racks and public art.

With all of the obvious solutions seemingly exhausted, Berg and the downtown business community had to get creative.

Enter the hawk.

Smarter than your average bird

As far as animals go, crows are near the top tier of intelligence. Their brains are oversized for their small bodies and it shows in their behavior. They communicate in complex and intricate ways. If one bird in the roost discovers a plentiful source of food, they'll go back and alert the rest. Sometimes, when one of them dies, a group will gather in a tree above their deceased kin in a kind of mourning. They've been observed using sticks to pry grubs from holes in logs.

Perhaps most impressively, researchers have shown that crows can remember people who wrong them, for up to five years, and pass that knowledge along to their offspring.

In the mid-2000s, John Marzluff, a wildlife biologist at the University of Washington and the author of "Gifts of the Crow," set out to study some of the birds on campus, as detailed in Audubon Magazine:

As they trapped and banded crows around the University of Washington's Seattle campus, he and his collaborators wore a latex caveman mask. When they later returned to those locations, either maskless or wearing a Dick Cheney mask the crows had never seen before, the birds ignored them. But anybody showing up in a caveman mask would spark a crowpocalypse. It wasn't just the trapped birds that responded; apparently others had witnessed the abduction and remembered it. Whole gangs of crows followed the evildoer, scolding and dive-bombing. The birds knew that caveman face, and they didn't like it one bit.

Like people, these birds hold grudges.

"I am still amazed by them — every time I look I see something different," Marzluff told The Oregonian/OregonLive. In crows, Marzluff has observed a wide range of behavior, including "language, delinquency, frolic, passion, wrath, risk-taking, and awareness."

And it's their intelligence that leads them to gather in great numbers in places like downtown Portland. Around dusk, they come together for what some call a "social hour." Starting around 4 p.m., thousands of crows gather in the trees along the waterfront or in the South Park Blocks or anywhere else that has large trees. They exchange information about where they've found food that day or predators they've encountered.

After about an hour of chit-chat, they move to a secondary location to roost for the night. The densely packed buildings provide light and warmth, two of the crows' top priorities when looking for a safe place to spend the night.

Once they find a place they like, they will call it home for an entire winter.

"The challenge is to manage the conflict between people and birds," Berg said. Other cities use pyrotechnics and physical hazing to deter the crows, but "we didn't feel that was right for Portland."

A 'Portland' solution

Once it became clear that the problem of the crow droppings couldn't be solved from below, Berg looked skyward.

Clayton, owner of Integrated Avian Solutions, has been working with raptors for 25 years. It started as a hobby in his teens when he began hunting ducks with falcons. His interest in birds of prey grew and eventually he turned it into a business, using peregrine falcons, gyrfalcons and hawks to chase nuisance birds — usually starlings, gulls and ravens — from vineyards and trash collection sites.

Last year, when Clayton brought in hawks as part of a pilot program to chase off the crows, it was his first experience flying his birds in an urban environment.

The Harris's hawk was the obvious candidate. In the wild, they are one of the few raptors to hunt cooperatively so they can work in teams. Any of his falcons would have likely gone after each other before they even noticed the crows.

Each bird is fitted with a light and a bell, as well as a tiny backpack loaded with a GPS tracker. The birds respond almost instantly to food, but on the rare occasion they don't come back, Clayton tracks them with an iPad he keeps in a fanny pack while he patrols the streets of downtown.

Sporting a neon green vest with "CROW PATROL" emblazoned across the back, Clayton walks the streets of Portland's business district for a few hours four nights a week, eyes trained upward for sightings of black crows against the black sky, ears scanning for the tell-tale sounds of crow flock.

It doesn't take much to scatter a flock. The hawks don't chase the crows, but they are seen as such a threat that even their presence in the area means it's time to move on. As soon as the hawks take flight, the crows nervously move off to safer territory.

The hawks are innate hunters with instinct to kill, but they've been trained not to and they pose no risk to the crows. They operate on a reward system and killing crows doesn't earn them treats from their handlers.

What does earn them treats is clearing crows and, in that respect, they've been quite successful. In their first year, the hawks easily cleared the designated area.

Now in their second year, Clayton and the hawks got started earlier, hitting the streets in late October, and are responsible for clearing a larger area — more than 70-square-blocks of the busiest area of downtown.

Kort Clayton is using hawks to drive problematic crows from the area shown on the map above.

On a recent mid-January night, it appeared that Clayton and his hawks were performing their duties almost too well. Over a few chilly hours, Clayton spent the vast majority of his time looking for crows to chase. Ditto for the two other teams of handlers and hawks patrolling the area.

The few flocks they did encounter were just outside of the designated area, right where they should be. And, according to Berg, the crow-related complaints have dropped.

"We feel like we've found the right solution to manage the issue," she said. "We've had fewer complaints. People are really satisfied when they see the result."

One of those people is Scali, the property manager. After she saw her building and the surrounding sidewalks thoroughly coated with crow droppings, she got in touch with the Portland Business Alliance, who called Berg, who let Clayton and the hawks know about the problem area.

They came and cleared the crows much more quickly than Scali anticipated.

"Literally within one day, they were gone," she said. "It was far beyond what we thought would happen."

-- Kale Williams

503-294-4048