And a Partridge in a Pear Tree?

If you’ve ever wondered how many black phoebes live along the Lower Arroyo in Pasadena, the answer is 27.

Well, approximately.

More accurately, 27 is the number of the small black-and-white birds spotted by Ron Cyger and Dan Lewis on a recent Saturday between 12:30 and 2:30 p.m.

As participants in an annual ritual known as the Christmas bird count, Cyger, president of the Pasadena Audubon Society, and fellow birder Lewis, a curator and archivist at the Huntington Library, counted 26 species and 387 individual birds in the Arroyo.

Over three weeks in late December and early January each year, thousands of Audubon members across the U.S. and Canada head to bird-rich spots in their areas and attempt to count not just the number of species but the actual numbers of birds. The annual event is, as the Audubon Society puts it, “citizen science in action.”

Since birds don’t sit still waiting to be noticed, the count is far from accurate. Birds often lurk deep in underbrush where they can’t be seen. They fly in and out of the count area, so it’s easy to count a single bird more than once or miss it entirely. And some counters are better than others at identifying birds.

But the Christmas bird count, or CBC, as it’s known to birders, is one of the few measurements over time of the status and distribution of birds in North America. Data for some areas have been collected annually for more than 100 years. In Pasadena (where this writer is an Audubon member), the count has been held each year since 1946.

While the actual numbers may not be reliable, it is possible to see trends in bird populations.

“It’s hard to get real continuity in counting, and the data are undoubtedly sloppy,” said Kimball Garrett, ornithology collections manager at the Los Angeles County Museum of Natural History. “But the point is, we’ve got 100-plus years of data for some regions and continent-wide data for 50 or more years. There are good data in the counts, especially when analyzed along with other studies.”

But as Garrett notes, birders are competitive, and that means “some groups work much harder on finding the rare birds in their area than on documenting the common ones. People go out and locate rare birds in the days before the count and then go re-find the bird on count day.”

Still, Garrett said, flaws and all, the counts have helped ornithologists analyze population trends over time, and that’s important.

“Certainly by the 1970s, when we realized that some species were really declining, you saw scientists really looking at the counts to see what data they could mine,” he said.

From the Pasadena counts, for example, it’s possible to see marked declines in spotted dove populations and increases in such species as Canada geese.

“Some species are going to get undercounted or double-counted more than others,” Garrett said. “You just have to hope you make the same errors from year to year.”

The count grows out of a 19th century tradition of Christmas hunting parties in which competing groups set out to see how many birds they could shoot in a day. In 1900, worried about sharply declining North American bird populations, ornithologist and Audubon member Frank Chapman started what he hoped would become a new tradition: a “Christmas bird census” in which hunters would count rather than kill birds.

In that first year, only 27 people participated in cities across North America, from Toronto to Pacific Grove, Calif. The combined counts yielded 90 species. Last year, the count drew nearly 50,000 participants in the U.S. and Canada. They counted more than 70 million birds of 660 species. This year, Pasadena Audubon members spotted 156 species in their count area alone, a circle 15 miles in diameter from a point at San Gabriel Boulevard and Duarte Road on the edge of San Marino.

Cyger, a probate manager for the Superior Court in downtown Los Angeles, started the count day at 5 a.m., persuading a Sierra Madre police officer to open a locked gate at the bottom of Big Santa Anita Canyon.

For the next hour, he drove slowly up the road to the ranger station at Chantry Flats, stopping frequently to get out and play a recording of owl calls, which he hoped would encourage real owls to answer. By 5:06, he had his first bird -- a great horned owl -- and by the time dawn broke, he had counted six great horned owls and one pygmy owl, identifying them by sound, which is allowed under count rules.

Once it was light enough, he headed for the five-mile Winter Creek trail, where he hiked and counted for the next five hours before going to the Arroyo to meet Lewis for several more hours of birding.

At a post-count dinner, Pasadena participants were generally pleased with the day’s results. Some good (translation: uncommon) birds had been seen, including two endangered California gnatcatchers and a type of woodpecker known as a Williamson’s sapsucker. People were enthusiastic about what they’d learned.

“We noticed that the scrub jays are really coming back after West Nile virus,” said 11-year-old John Garrett (no relation to ornithologist Kimball Garrett), whose list of birds he has seen boasts 389 species. “We saw 47 scrub jays, which was great.”

Marge Lyons, an 83-year-old retired Maryknoll nun, looks forward to the annual counts. Some of the nuns she lives with at an estate in Monrovia feed wild birds. “But I don’t believe in that,” Lyons said. “There’s too much out there for them.”

Her friend, Maryknoll Sister Theresa Lisak, 75, had come from San Diego for the count. Lisak says that for her, birding has a strong spiritual component. “There’s real meditation in it,” she said.

This year’s count held a few disappointments, as it does every year, said Jon Fisher, a Disney production coordinator who organizes the day’s activities. Several species usually found were not observed, including marsh wrens and American dippers, the only North American songbirds that swim.

But the list of missed species was relatively short, and Fisher was pleased with the final tally. “It’s an important contribution that average birders who do something else five days a week can make,” he said.

Patrick Barmann, 9, and brother Andrew, 11, joined their grandmother to count birds in Arcadia’s Bailey Canyon. On balance, they liked it.

But Patrick said he thought Disneyland was more fun.

When it was pointed out that there aren’t many birds at Disneyland, he replied: “Haven’t you heard of Donald Duck?”