Audubon's 108th Christmas Bird Count will start Friday. Thousands of bird-watchers within the Western Hemisphere will take to the field to count birds.

Here in Utah, somewhere between 300 and 500 people will participate in the count.

The counting period will end Jan. 5.

This is the longest-running wildlife census in the world and has become an annual tradition for citizen science volunteers in communities throughout the Americas. The data collected enables Audubon and other conservation partners to assess the status of birds and habitats vital to birds.

Last year's data helped reveal population declines among many birds. Issued in June, Audubon's Common Birds in Decline analysis focused new attention on habitat loss, climate change and other threats facing familiar birds.

The count offers ways people can help keep common birds common. Christmas data is also instrumental in developing a WatchList, a collaboration between Audubon and the American Bird Conservancy that identifies less common birds whose small and declining population sizes and limited range put them at imminent threat of extinction.

According to C. Val Grant, president of the Bridgerland Audubon Society, the count focuses on a 15-mile circle. Each of those involved is assigned an area within the circle.

"Some will go out and brave the cold nights and count owls. Others will start at dawn and go until sunset and count all the birds they see," he said.

Final totals will be submitted to a national collection point.

Among the more common birds Grant expects to see here in Utah are starlings, ducks, geese, eagles and finches.

"This year we also expect to see the Bohemian waxwing. We haven't seen this bird for a while, but a lot have come into Utah this winter," he noted.

Counting birds is the first step in learning how environmental threats are affecting birds and in understanding what needs to be done to protect the birds.

New analysis of count data will focus on how populations or ranges may be changing due to the effects of global climate change. The proverbial "canaries in the coal mine," birds provide an early warning indicator with respect to the health of the global climate.

The Christmas count began more than a century ago when 27 conservationists in 25 localities, led by scientist and writer Frank Chapman, changed the course of ornithological history. On Christmas Day in 1900, the small group posed an alternative to the "side hunt," a Christmas day activity in which teams competed to see who could shoot the most birds and small mammals.

Chapman proposed that they identify, count and record all the birds they saw, founding what is now considered to be the world's most significant citizen-based conservation effort.