"Hot dog!" cries Doris McGovern. At 5:30 in the morning, it's pitch black outside as her red Subaru station wagon lumbers through the brush at the John Heinz National Wildlife Refuge near the airport.

She and fellow ornithologist Alice Sevareid just spotted an American Woodcock. To me, all the birds we see in the first hours of the 20th annual Philadelphia Mid-Winter Bird Census pretty much look the same—specks on the lake or silhouettes against the sky—but, magically, this time the headlights pierce through the cold morning air to illuminate a chunky bird with camouflage plumes and an orange breast.

Although it's rare to get so close—we nearly run the little guy over before he "flushes," or flies off in a tizzy—my guides aren't surprised to find him so early in the day. For one, the Audubon-designated Important Bird Area at Tinicum is one of the few places woodcocks live in Philadelphia and, two, McGovern says the birds like to probe the "mushy, gushy" ground here with their long bills.

"If you don't find them here, you certainly won't find them in Center City," she says, "unless they run into an office tower, which they often do. Then you find them on the streets of Center City."

We hear few noises except birdcalls, the ever-present whir of planes taking off, the beeping of a truck backing up somewhere and cars zipping by on Interstate 95. A telescope peering through the clear sky reveals Jupiter and three of its moons, while dozens of deer and the occasional jogger run free. "All this, and just minutes from the city," McGovern says. "Fabulous."

Although she predicts an "un-birdy day," the women manage to identify 45 species before calling it quits. With about three-quarters of the 24 teams reporting, census founder and coordinator Keith Russell compiled a list of 99 species spotted in this year's count, which works out to tens of thousands of individual birds.

It's hard to know what factors—temps in the 20s probably played a role—kept commonly spotted birds such as the Fox Sparrow hidden, says Russell. The biggest change is the loss of wetlands, open fields, meadows and other farmland-type habitats (think development, airport expansion) that have brought the Ring-necked Pheasant, for example, to the edge of extinction in this area, he says.

The purpose of Russell's census, which, unlike the well-known National Audubon Society's Christmas Bird Count, includes only land inside the city limits, is to document the city as "one of the most diverse wintering bird populations of any location in the state." Proximity to the Delaware and Schuylkill rivers and the mix of forest and aquatic habitats make it fertile bird country.

Besides increasing interest in the part sport/part science art of bird watching, Russell's goal is conservation. In the mid-1990s the data helped him convince the Water Department to stop draining a reservoir in Strawberry Mansion to preserve waterfowl habitat.

Ornithologists, binoculars at the ready, scan the sky in Germantown, Mt. Airy, Penn's Landing and other areas; the most species are typically recorded inside Fairmount Park and Benjamin Rush State Park. Russell will eventually compile the findings in a report for the Delaware Valley Ornithological Club (www.dvoc.org).

"It may seem weird," he says, "but it does provide information we wouldn't be able to get any other way."