Results from the ninth Christmas Bird Count in Sonoma Valley indicated fewer birds than in the past years, but new species were seen during both the daylong count and the half-day Christmas Bird Count 4 Kids.
Nearly 90 birders surveyed a circular area 15 miles in diameter, centered near Arnold Drive and Orange Avenue, covering most of Sonoma Valley and the City of Petaluma, for the Dec. 27 Christmas Bird Count. The diverse habitats within the circle include the Petaluma and Sonoma watersheds, mountain ranges and wetlands, with influences of not-so-distant urban areas and San Pablo Bay also observed.
Tom Rusert and Darren Peterie began the Sonoma Valley branch of the national event in 2004 after realizing the uniqueness of habitat and the bounty of birds in the area. Rusert said Sonoma Valley’s bird count is ranked among the very best in the nation, both in overall species recorded and in individual participation by local citizens and landowners. “We’re glad to have so many participants in this citizen science, and to have access to private land makes a world of difference,” Rusert said. “People have been helpful letting us go onto their property and then coming out with us.”
The annual count takes place on the Friday after Christmas and is a “census” of birds and species over a 24-hour period. The birds are tallied and totals are submitted to the Cornell Lab of Ornithology eBird program, the largest database of recorded bird locations in the world. More than 400 species of birds, according to Rusert, have been officially recorded in Sonoma County over the last several decades – 800 to 900 bird species have been recorded in the nation. In Sonoma Valley, 200 species of birds have been identified.
“The preliminary results of species groups showed reduced numbers compared to the past eight years,” Rusert said. Birders counted 155 species on Dec. 27 in the 24-hour period beginning at midnight.
Over the last eight years, according to the bird count’s new data compiler, Gene Hunn, the Valley’s bird count averages 163 species. The total number of individual birds counted was 57,791, or 84 percent of the eight-year average 68,843. Rusert speculates that last year’s drought may have played a factor in the reduced numbers. “The unusually dry winter changes the formula,” he said.Hunn said high tides, wind, temperature and food sources can also influence a species abundance.
For example, Rusert explained, blackbirds were down 30 percent, shorebirds were down 51 percent, herons and egrets were down 60 percent, and sparrows and towhees were down 78 percent.
But some species groups proved stable, and even increased, he said, explaining a 150 percent increase in woodpeckers and thrushes, a 94 percent increase in owls and a 123 percent increase in crows and ravens
New species never seen in previous years were recorded in the count, Rusert said with excitement. Species included the Iceland gull at Shollenberger Park in Petaluma, the northern saw-whet owl, discovered in two locations in the Mayacamas Mountains, and a black-headed grosbeak, discovered in the upland section of Wingo. “It has taken nine years to discover this species in Sonoma Valley on the day of the count,” Rusert said of the owl. The group also recorded the hard-to-spot burrowing owl and the rare spotted owl.