Snowy owls, with 5-foot wingspans and piercing yellow gazes, are a rare sight in this region, so far from their high Arctic realm.
Last winter, however, the majestic birds showed up in numbers not seen in half a century. Birders declared it a once-in-a-lifetime event.
Incredibly, it is happening again. The owls are back this winter, if not quite as abundantly.
Their appearance over the last two years has sent researchers into a frenzy of data-gathering on a species that has given up little about where it goes, what it does, and why.
During snowy owl "irruptions," unusually high numbers travel south for the coldest months, out of Canada and into the United States. The phenomenon is not well understood but is thought to be related to population changes in Arctic lemmings, a preferred food. When the lemming supply peaks, the owls have more young, which then venture farther afield.
"They're still a real puzzle," said Scott Weidensaul, a Schuylkill County naturalist and author who was instrumental in hastily mounting an unprecedented research effort by dozens of scientists, called Project SNOWstorm.
Earlier this winter, one of the huge owls was spotted in a Berks County subdivision. Another was photographed on an Avalon rooftop. More have delighted birders who make the cold trek to the dunes at the undeveloped southern end of Long Beach Island.
The Jersey Shore has been a sighting hot spot, presumably because the open beaches resemble the snowy tundra of the owl's far-north habitat. So do the snow-covered farm fields of central Pennsylvania. But to their dismay, scientists have realized the owls also are drawn to the open spaces of airports, where things often end badly for them.
In the mid-1920s, during a mega-irruption, humans celebrated the spectacle by shooting the owls. This time, researchers are catching them with a bow net trap - like an oversize mousetrap with a net - and strapping transmitters to their backs.
Although Project SNOWstorm is a volunteer undertaking, the tracking technology is costly. So, last winter, scientists scrambled to set up an ongoing crowdfunding drive on Indiegogo, with an initial goal of $20,000. They quickly blew past it - partly the result, they postulate, of the owl's fame as Harry Potter's Hedwig.
Happening without notice, leaving no time to apply for grants, irruptions "go unstudied more often than not," said David La Puma, director of the Cape May Bird Observatory, who passed up a winter vacation to work on the effort. "I hit up everyone I knew. I knew from the beginning this was going to be a win."
The technology has advanced dramatically. Cellular Tracking Technologies, a Western Pennsylvania company that makes wildlife tracking devices, recently developed a transmitter that can gather data on latitude, longitude, and altitude accurate to a fraction of a meter. The tiny instrument sends data when the bird is within range of a cellphone tower; solar-powered, it should last a dozen years or more.
Last winter, there was enough money to place transmitters on 22 birds. This year, that number should go up. Project SNOWstorm - incorporating the four-letter identification code ornithologists use for the snowy owl - has a Facebook page and a website with data from the transmitters.
And what stories the devices have revealed.
Scientists were fascinated last winter by the peripatetic movements of a snowy owl they named Assateague, for the Virginia spot where it was captured. No surprise, it stayed over land by day. But by night, it soared over the bay and ocean, presumably nailing sea ducks for dinner.
So far, five of the 22 birds fitted with transmitters last winter have returned this year. On Feb. 1, as the first owl finally came within range of a cell tower - nonexistent in their breeding ground, in the highest latitudes of the Northern Hemisphere - the scientists watched enthralled as the massive data dump began.
"Every time we get one of these transmissions, I feel like a little kid at Christmas," Weidensaul said. "We have these wonderful tracks of these birds" going up to the shores of the Beaufort Sea and other Northern realms few humans can reach.
Because the owls are nomadic, researchers have trouble counting them. They once thought the population was 200,000 to 300,000 but now believe it could be as few as 30,000.
Sometimes, the transmissions tell sad stories.
Snowy owls that venture into our world meet up with planes, automobiles, and electric wires. In one case, a bird captured at Philadelphia International Airport was tagged and released, presumably out of danger, in Lancaster County. But it flew back to the airport and was hit by a plane.
Two others with transmitters drowned in a storm off the Massachusetts coast. The device led a researcher to the remains of one buried in the wrack line on a beach.
Snowy owls that die and are recovered have been sent to the Penn Vet Laboratory of Avian Medicine and Pathology, a facility that deals primarily with poultry, at the New Bolton Center in Chester County. In necropsies, veterinarians have analyzed the livers and kidneys for heavy metals; taken bacteria cultures, and fungal and fecal samples; collected lice; plucked feathers to look for toxins; measured wings, beaks, and talons; and snipped tissue samples for genetic studies to determine if snowy owls have distinct lineages.
Of 27 dead owls taken to the Penn Vet lab, 13 had succumbed to trauma, presumably hit by a car or plane. One had been electrocuted. More than a third had evidence of rodenticides, probably from eating rodents containing the poison. Nearly half had pesticides in their bodies, though it was unclear where the chemicals came from, and whether the levels were enough to have killed the birds.
Penn's Sherrill Davison, who led the necropsy effort, found it intriguing that most of the birds recovered from New England were in poor condition, with "more disease issues" than those from the Philadelphia region - suggesting the frailer birds couldn't make it this far.
The necropsied owls will be given to institutions, including two to the Academy of Natural Sciences of Drexel University. Even in death, they will be ambassadors for their species and their Arctic habitat, where response to climate change is pronounced.
To La Puma, of the Cape May observatory, one of the best things about Project SNOWstorm has been the public engagement. "I'm confident we increased the scientific literacy of a massive number of people, when most people aren't even looking at birds," he said.
"When a bill comes up to protect open space, these folks are going to remember the snowy owls that visited those farmlands and say, Yeah."