The Audubon Christmas Bird Count is the longest running citizen science project in the world, and it's almost time to start the annual tally once more. And while thousands of nature-lovers regularly volunteer for the three-week-long project, Audubon is hoping this year's turnout will be the biggest yet.

Local and regional Audubon chapters have been hard at work getting the word out about this year's count. The collected data -- sourced from groups of hikers and bird-lovers all over the country -- is vital for researchers, conservation biologists, ecologists and other scientists keen on better understanding the long-term health of North American bird populations.

Compared, contrasted and combined with the annual Breeding Bird Survey, the Christmas Bird Count numbers offer a wide angle view of the continent's winged species, their changing numbers and habitat preferences plotted across time and space.

The numbers -- collected now for more than 115 years -- are retrieved, combined and organized by scientists working with the national Audubon Society and Cornell University in Ithaca, New York.

"For over one hundred years, the desire to both make a difference and to experience the beauty of nature has driven dedicated people to leave the comfort of a warm house during the Holiday season," Audubon officials wrote in a press release this week.

"From feeder-watchers and field observers to count compilers and regional editors, everyone who takes part in the Christmas Bird Count does it for love of birds and the excitement of friendly competition," Audubon added, "and with the knowledge that their efforts are making a difference for science and bird conservation."

Even thought the official count hasn't begun, some local chapters are already hosting events. A California nature center in Napa Valley recently lead a group of kids on a holiday hike to look for and count birds.

"When you go out on a Christmas Bird Count, you don't have to be an expert," Wendy Schackwitz, the Napa-Solano Audubon president, told her fellow hikers on their weekend expedition. "You just have to be a set of eyes to help the experts find the birds."

It's a message Audubon officials hope more people hear.