Starting Monday, local volunteers will join bird enthusiasts across the country in measuring local bird populations as part of the 110th annual Audubon Christmas Bird Count.
Every year, thousands of people nationwide count the birds to help Audubon track the progress of imperiled species and gauge the impact of environmental threats to birds and habitats.
It's the longest-running wildlife census in the world, according to the organization.
More than 5,000 Californians are expected to participate in about 100 counts statewide, including ones in Alameda County and also in Sonoma, Santa Cruz, Santa Clara, San Francisco, Marin, Monterey, San Mateo and Contra Costa counties, according to Audubon California.
For each count, volunteers join at least one experienced birdwatcher and count birds within a 15-mile-diameter circle
The count began as an alternative to holiday hunting contests, according to Audubon California.
In 2009, the group used data from decades' worth of counts to determine that climate change will likely cause up to one third of California's native bird species to experience significant reductions over the next 30 years or so.
Potential participants can go to www.ca.audubon.org or call Garrison Frost at (510) 601-1866 to find a local count.