Susan Miller is used to spotting birds on her nature walks.

That makes the Plum naturalist a perfect candidate for the annual Christmas Bird Count, a worldwide effort to document local bird populations.

The survey is the largest citizen science effort held for one day, between Dec. 14 and Jan. 5, throughout the United States, Canada, Latin America, the Caribbean and the Pacific Islands.

Data from the counts, as well as from two other annual counts, the Great Backyard Count in February and the Global Big Day counts in May and October, is submitted to the Cornell Lab of Ornithology in Ithaca, N.Y. The data is used in the lab’s mission to study and monitor the health of the world’s roughly 10,000 bird species.

Miller takes part in bird counts at the Bushy Run Battlefield area and in Rector, both in Westmoreland County.

“Last year in Rector, my group and I saw 900 Canada geese swirling around together in the sky like a tornado,” Miller said. “It was as if they couldn’t decide which way to go. Finally, they broke off in groups of a couple hundred and flew way in the same direction. It was exciting to watch.”

The count has its roots in the formation of the nonprofit Audubon Society, as hunters in the late 1800s and early 1900s began to realize the damage being done by over-hunting birds.

The Audubon Society has been hosting the bird counts for 125 years. Society-hosted counts will take place at the following locations and dates:

• Dec. 7 will be a “warmup” event from 2 to 4 p.m. at Buffalo Creek Nature Park, 154 Monroe Road in Sarver. Beginners will take a bird hike — complete with coffee and bagels — as they learn about counting birds for scientific research.

• Dec. 14 in Buffalo Township, including Todd Nature Reserve and Buffalo Creek Nature Park. For meet-up times and to register, email g.reese@gaiconsultants.com. There will also be a Kids Christmas Bird Count event at 10 a.m. at Buffalo Creek Nature Park.

• Dec. 15 at locations in the Mon Valley. For meet-up times, locations and registration, email nstahlman@aswp.org or call 412-904-7495.

• Dec. 28 in Pittsburgh. For meet-up times, locations and registration email bshema@aswp.org or call 412-963-6100. There will also be a Kids Christmas Bird Count event at 10 a.m. in the Beechwood Farms Nature Reserve, 614 Dorseyville Road in O’Hara.

• Dec. 29 in southern Butler County including the Succop Nature Park, 185 Airport Road in Butler. For meet-up times, locations and registration, email ckubiak@aswp.org or call 412-963-6100. There is a Kids Christmas Bird Count event at 10 a.m. at Succop Nature Park.

• Jan. 18 there will be a presentation recapping the results of the second annual bird count held in the newly added Mon Valley study area. It will be at 10 a.m. at Renziehausen Park on Pin Oak Drive in McKeesport.

Miller said anyone with a home bird feeder can help out bird counters by filling it between Dec. 14 and Jan. 5, when count events will be taking place.