Armed with binoculars, spotting scopes and pen and paper, scores of birders fanned across the west county looking — and listening — for the likes of the red-breasted sapsucker, the varied thrush and the ruby-crowned kinglet.

Of course, if a more common California towhee or dark-eyed junco flew by, they, too, would be counted. But birders like Jeff Holtzman of Sebastopol were clearly out Sunday for the “Wow!” moments.

“To me, it’s an avian scavenger hunt,” said Holtzman. “There are many beautiful surprises that await you.”

Holtzman took part in the 48th annual West Sonoma County Christmas Bird Count, one of about 2,000 bird counts held across the United States during the Christmas holiday.

The holiday bird counts are aimed at calculating bird populations at a time when migrating and native birds are “wintering,” said Peter Leveque, co-leader of the west county bird count, which is conducted for the Madrone Audubon Society.

“The reason we do it at Christmas is because birds are now where they are going,” Leveque said, adding that many of the migrating birds in the area have come from breeding territories as far away as Alaska, western Canada or Washington and Oregon.

Sunday’s count in the west county covered an area bounded by waters of the Pacific Ocean to the west, Guerneville on the north, Freestone to the east and the Estero Americano to the south.

That territory is further divided into just under 20 smaller territories. On Sunday, Leveque organized Holtzman and about 10 other b irders who surveyed an area along three miles of the Russian River, from Monte Rio to Freezeout Canyon.

At about 10:30 a.m. Leveque’s group met at the beach of the Casini Ranch Family Campground in Duncans Mills, where the birders covered the campgrounds on foot. Holtzman was joined by three other birders, Hillary Smith of Penngrove and Andy Kubersky of Sebastopol.

Smith, who runs a landscape and garden business called Earthly Delights Gardening, is an avian biologist who used to work for the Institute for Bird Populations in Point Reyes Station. Smith said that when she entered the Casini Ranch campground she saw a ruby-crowned kinglet, a species she doesn’t get to see often.

“Usually you just hear them going, ‘Jeh-dit, jeh-dit, jeh-dit,’” she said. “But this guy fluttered about, came out of the bush and regaled me with his full-on crimson red cap,” she said, adding that the exhibition was essentially the bird asserting its territory.

Smith said that birds can be counted simply by hearing their song.

Leveque said the count is a way of tracking trends, including the disappearance of certain bird species. For example, the loggerhead shrike, though never abundant, was usually always spotted. Now, it is no longer seen in the area. The western meadowlark was more abundant in the 1960s and 1970s than it is now.

One bird that recently moved into the area is the Eurasian collared dove, which competes with the native mourning dove. The Eurasian collared’s numbers have been increasing, even as the population of the mourning dove is on the decline, Leveque said.