Flying Monkeys

Crows acting up, by Greg7

“Why don’t you just shoot them?”

That’s the reaction of most homeowners when Grant Stokke asks permission to live trap American crows in their backyards. But he hastens to add that they do give him permission.

Stokke is a graduate student who is working with Dr. Margaret Brittingham, professor of wildlife resources at Penn State University, to try to understand the dynamics of winter crow roosts in Pennsylvania, specifically one in and around the city of Lancaster.

I joined Brittingham, Stokke, and field assistant David Burkett for a day of crow field work last January after reading about attempts the winter before to chase the birds from their winter roost in suburban Lancaster County. That winter three townships had called in the United States Department of Agriculture’s Wildlife Services to set out poison bait, which didn’t work very well and angered citizens who opposed using a toxic chemical to kill crows.

Lancaster isn’t the only mid-sized city adjacent to agricultural fields that supports winter crow roosts. Harrisburg, Bethlehem, Scranton, and most recently Lebanon, have a similar problem. So too do a host of other places from Auburn, New York to Riverton, Wyoming.

Most places have tried a combination of noisemakers, shooting, distress calls, and other harassment techniques such as hanging dead crows from trees at their roost site as Lancaster County did the previous winter to chase them away. Sometimes the crows leave, but usually they return.

After all, crows have always formed winter roosts. They used to be in the country, but now that we have provided well-lit malls and city streets that keep away crow predators, specifically their nemesis — the great horned owl — and which are close to agricultural areas that provide food during the day, crows spend the long, dark, winter nights close to humans. Unfortunately, they are not only noisy but incredibly messy, covering buildings, sidewalks, and cars with their excrement.

In the Lancaster area, the crows begin arriving the second week of November and build up their numbers in December. To find out where they are coming from, Stokke and Brittingham have collected stray feathers from American crows, which they subjected to hydrogen ion testing. The test indicated that those crows were in Canada when they grew their feathers, proving that winter roosts consist mostly of migrant crows.

Kevin McGowan, who has been studying American crows in and around Ithaca, New York, since 1988, writes that several of the birds he has tagged there, “have been shot or seen in Pennsylvania during the winter,” so at least a few of the crows come from New York state.

Furthermore, Stokke and Brittingham have discovered that about 25 to 35% of the local crows will occasionally join the roost.

“They will roost at the communal roost some nights and within their family home range the rest of the time. The other 70 to 75% roost within the family home range all the time,” Brittingham said. This finding directly contradicts McGowan’s research in Ithaca in which he found that winter roosts there are made up of migrants and locals and that all locals join the roost.

“I don’t know why there is a difference with Ithaca,” Brittingham said.

“There Is A Light,” by CrowHand

But knowing where they come from doesn’t solve the problem. That’s why Stokke and Brittingham, in their crow behavior study — “Ecology and Management of Urban Crows in Pennsylvania” — are working with local citizens’ groups, local, state and federal government officials, and colleagues at Franklin and Marshall College “to develop a multifaceted approach to reducing the crow problem,” Brittingham said. “But,” she added, “there’s got to be some place for them to go.” Ultimately, Stokke said, they are “looking at whether we might create a place to attract these crows where they won’t be so much of a problem.”

Last winter, instead of poisoning crows, USDA Wildlife Services trained citizens in a variety of harassment techniques including shooting blanks at the birds. First, this harassment moved them from a suburban area northwest of Lancaster, which includes the Park City Mall, where the crows roosted on their 10-acre roof and pecked holes in it. They also made a mess of cars in the parking lot.

Then the crows congregated in center city Lancaster for two weeks. That, Stokke told us, was a rough neighborhood, but still the citizens continued their harassment.

The plan was to move the crows to a county park southwest of Lancaster. It was ideal crow habitat, they thought, but the crows didn’t agree. Instead, they circled and returned to the original northwest light industrial area near farm fields, and that’s where Brittingham and I met up with Stokke and Burkett.

They had already done their pre-dawn roost count, which they estimated to consist of 30 to 35,000 crows. Of those, ten to 20% are the smaller fish crows and the rest are American crows. So far they don’t know where the fish crows are coming from, although Brittingham said that, “Wildlife Services banded a lot of fish crows so we may eventually figure that out.”

Stokke and Burkett also drive a daily route to see where the 42 radio-tagged American crows, half of which are locals and half migrants, spend their days. They took us along for a portion of their route. At the edge of a field across from a housing development, the radio buzzed as we approached an American crow with a white antenna affixed to its back.

“That’s the first one I trapped,” Stokke said. He discovered that this local American crow family of nine or ten birds has less than a square mile of territory. They rarely leave it, although at least two crows did join the Lancaster roost for one night. Such information is hard won, because trapping American crows is not easy, as we found out.

Crows eating French fries, by Greg7

The bait that day was ground beef and peanuts in the shell, but usually it is hot dogs and Chitos, which are cheaper, Stokke told us. At the edge of a corn field, they spent many minutes setting up a portable trap designed by USDA’s Wildlife Services and then carefully camouflaging it with dried grasses. We retreated to their sport utility vehicle and waited for an hour.”All it takes is one brave crow and the rest are in,” Stokke said.

But not one crow came near the trap, not even a fish crow.

These smaller crows, Stokke explained, are easier to trap but they have to release them because the radio-tags are designed for the heavier American crows.

We moved on to a backyard across from a Barnes and Noble bookstore. Cars streamed past on nearby U.S. Route 30 and the Fruitville Pike. A line of tall trees divided the backyard from a corn field. Another copse of trees split the corn field, and it was there that the crows had congregated. We watched for an agonizingly long time as first one crow, then another, flew into the backyard trees for a look at the bait. Finally, one landed near the trap.

“One healthy bird, glossy feathers, lots of body fat,” Brittingham commented. She figured that it was too well-fed to be tempted by their bait. Usually it was a great place to trap crows, but the birds often outsmart them according to Stokke.

While we watched, the crows continued to fly over the bait, but no more birds stopped to look. I felt as frustrated as the researchers.

“They don’t look hungry,” Brittingham said.

By then the crows were engaged in what the scientists call PRA (pre-roosting aggregation) or staging in groups away from the roost, and everywhere we looked we could see flocks of crows calling and chasing.

“I think of them as flying monkeys,” Stokke said, “because they are so smart.” Other researchers agree that the crow family in general is incredibly intelligent. Carolee Caffrey, who studied American crows in Oklahoma, watched a male crow shape a piece of wood into a probe by pecking at its tapered end. He then stuck it into a fence post knot to extract a spider lurking just beyond the reach of his bill.

Caffrey also watched a female American crow defend her nest from a climbing researcher by breaking off pinecones and dropping them on the climber’s head. Altogether, she hit the researcher three out of four tries.

American crows are also the ultimate family-value birds. They mate for life, live in family groups, and older siblings often help feed and protect their younger brothers and sisters. Unlike most other wild creatures, adult American crows never chase away their offspring. When they do leave their family, they return frequently to visit. McGowan, in Ithaca, reported that “one individual (less than one year old) was seen at a compost pile in northern Pennsylvania with a flock of crows, and three weeks later it was back in Ithaca with its parents who were starting nesting. It helped the parents raise young that year, and remained in the area over subsequent winters.”

As the afternoon waned, crows flew more purposefully toward the roost area. In the distance we heard the “pop” of blanks being shot by citizens using nonlethal harassment techniques. The light industrial area hardly looked like a natural area. Under a single conifer surrounded by business buildings, Stokke spotted a banded dead crow. It was not one of their bands so he copied down the number and removed a tail feather for hydrogen ion testing. He also examined it for injuries and found none. The crow was stiff, covered with excrement, and had probably died on the roost the previous night.

The service manager for a nearby car dealer emerged from the back door, and when we told him what we were doing, he launched into his own crow woes. The crows had been using their roof for two weeks.

“We’re just not happy about it,” he said. “They hit a lot of new cars when they take off in the morning — “cars they have to wash before customers arrive.

Eventually, driving through a maze of linked roads behind business buildings, we reached the back of loading docks where we parked. On one side beyond the parking lot were a cattail-filled wetland, a line of tall trees, and the backs of substantial new homes. In front of us was a posted, chain link fence. Beyond that was a large grassy area and then a cement factory.

A crow roost in State College, Pennsylvania, by mandy whale

Standing behind the fence, we watched in awe as a glorious sunset lit the thousands of crows flying in from all directions. Many alighted on the flat-roofed buildings, cawing loudly. Others landed in the line of trees along the wetland, disturbing a large flock of Canada geese that joined the general hubbub and flushing a great blue heron.

What a spectacular, yet ludicrous sight. Stokke, who had previously studied common ravens in a remote area of Washington state, could not imagine a more stark contrast to his present situation — malls and business buildings, housing developments, and crushing traffic.

Yet nature persisted and, in fact, preferred the city/suburban landscape. In our rush to expand and develop we had created ideal winter habitat for the gregarious, intelligent crows. Safe from predators and warmed by the “heat bubble,” rising from the buildings which can be five to ten degrees higher than the surrounding countryside, the crows slowly settled down for the night.
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To learn how you can support local volunteers in Lancaster and protect the crows from lethal management, visit the website of the Lancaster County Crow Coalition.

All photos used by permission.