It was just another Center City killing, except it happened in broad daylight and a crowd gathered to watch. An adolescent red-tailed hawk landed on the roof of a black car near Eighth and Market, sank its talons into a pigeon, and proceeded to chow down.

Feathers and entrails flew. Video phones were deployed. Bystanders groaned. The bird, unfazed, kept eating.

Then, having finished its meal, the hawk flew to a nearby lamppost for a postprandial nap, leaving the returning motorist to deal with the bloody pulp and fluff scattered atop the car.

That close encounter with nature - red in tooth and claw, and vividly captured on a YouTube video - was certainly dramatic, but such hawk sightings are no longer rare in Philadelphia.

So many YouTube videos document hawk kills in the city that they practically constitute a genre. Besides recording the mayhem on Market Street, humans have filmed hawks in mid-bite in Rittenhouse Square, on the University of Pennsylvania campus, in the Philadelphia Museum of Art's sculpture garden, and in the yards of Bella Vista rowhouses. One local bystander narrowly missed becoming collateral damage when a large redtail dived for a squirrel outside the museum. The squirrel got away.

One reason for the run-ins with redtails is that raptor populations have made a remarkable comeback in the last five years, and they've done so, ornithologists say, by moving into downtowns. Once a habitué of North America's grasslands, hawks have discovered that cities are safe places to raise a brood, and they offer a 24-hour smorgasbord of pigeons, rats, and squirrels.

"We have a pretty good view of Logan Square, and we see them hunting all the time," said Dan Thomas, who manages the bird collection for the Academy of Natural Sciences. Not long ago, he added, a colleague went to fetch the academy's van from the alley behind the museum only to discover a Cooper's hawk enjoying a pigeon on the roof.

There was a time when a person couldn't get within 10 yards of a hawk kill, said Kevin McGowan, a scientist at the Cornell Laboratory of Ornithology in Ithaca, N.Y. That may still be the case in rural areas. But as hawks settle in cities, they've grown more accustomed to people.

The fact that a bird would even allow people to watch it eat, McGowan said, suggests that hawks have undergone a "culture change" to adapt to life in the big city. Even so, several scientists who watched the video of the adolescent hawk on the car wondered whether an older, more mature bird would have found a quieter place to dine.

Still, real changes in hawk behavior continue to be documented. Not long ago, a pair of redtails built a nest in the stands at Boston's Fenway Park, only a few feet from the roaring crowds. The birds had to be evicted, however, after one pecked a young fan on the head for straying too close to the chicks. Adult redtails can have a wingspan of four feet and weigh two to three pounds.

As the birds become more visible in urban areas, they've also become the darlings of the media.

After a pair of redtails were discovered nesting on a window ledge at the Franklin Institute in 2009, the museum installed a webcam and posted their antics online, turning them into an Internet sensation, with a "Hawkaholics" blog and a Facebook page. A similar pair in New York, known as Pale Male and Lola, have inspired books, films, and countless websites since they set up housekeeping on a Fifth Avenue building.

The media's focus on such high-profile couples might suggest that downtown hawk nests are an aberration. In fact, a quick web search finds that virtually every American city can claim at least one prominent nest. The easy availability of raptor-friendly high-rises allows them to produce chicks in a safe environment. As they send them into the world, the urban population grows quickly.

In just the last two years, the Franklin Institute hawks have produced six chicks, and they are preparing to nest again, said the museum's president, Dennis Wint. Meanwhile, in New York, the tony real estate around Pale Male's Fifth Avenue home, across from Central Park, has become so saturated with hawks that some fledglings had to find new hunting grounds. They established a downtown colony in the edgier East Village.

As much as they like roosting on high-rises, hawks are happy to make their home in low-rise areas. Alex Kanevsky and Hollis Heichemer, artists who live in Bella Vista, looked up from their work recently to spot a Cooper's hawk tearing into a pigeon in their small rowhouse garden. The bird has returned several times.

"We never saw a hawk here until this winter," said Kanevsky.

The hawk catches its dinner elsewhere and retires to their yard to eat. "Then he spends the rest the day here, digesting," Kanevsky said.

Joan Morrison, a biologist at Trinity College in Hartford, Conn., believes that hawks are now as much urban birds as pigeons or sparrows.

In addition to redtails, she said, Cooper's hawks, sharp-shinned hawks, Harris's hawks, and merlins "are moving into and taking up residence in urban areas throughout the U.S." What's more, bald eagles - a close relative of the hawk - "are expanding almost exponentially throughout the lower 48."

Red-tailed hawks, added McGowan, the Cornell ornithologist, have doubled in number since 1966, thanks in part to a shift in their image.

Once reviled by farmers as vermin because of their taste for chickens, redtails were relentlessly hunted, leaving them close to endangered. But as the practice of keeping henhouses declined, the hatred faded.

Then after the pesticide DDT was banned in 1972, the survival rate for hawk chicks shot up. McGowan also has documented a similar bump in the crow population, although he noted the species prefers the suburbs, where lawns offer a rich supply of earthworms.

"We're now recovering from the worst trashing of wildlife this continent has ever seen," he said. "You see more wildlife on a daily basis than your grandparents ever did."

In the coming years, Morrison predicts, we'll be encountering hawks more often. With hardly any human or environmental predators, their biggest threat is getting hit by automobiles as they dive for prey. Hawks also can succumb if they eat a rat or pigeon that has ingested poison.

But as their population grows, it's only natural that hawks will congregate in vermin-rich cities. Red-tailed hawks must eat the equivalent of one pigeon or rat a day, making them a great form of pest control, said John A. Blakeman, a licensed master falconer in Ohio, who has studied the bird's habits for four decades.

"You you don't see redtails flying after their prey," Blakeman explained. "You see them sitting on a telephone pole. It looks like they're just passing the time, but they're using their binocular eyeballs to look at everything. If a rat comes out, the bird can see it."

And after the hawk snares its catch, there's always a nearby car available on which to eat it.

Contact staff writer Inga Saffron
at 215-854-2213 or isaffron@phillynews.com.