Without the binoculars, the bird is but a white speck moving in and out of the waves in the distance. With them, it counts as one gull.

The below-freezing weather and impending snowstorm didn’t stop the bird from diving into the sea for fish, nor did it deter the two bird-watchers. Wearing skullcaps and thick gloves, Dean of Undergraduate Admissions Jeff Brenzel and East Rock Park ranger Dan Barvir traveled over frozen mud, stiffened grass and sharp brambles around the New Haven harbor to count individual birds and bird species on Dec. 19.

Brenzel and Barvir were gathering data for the National Audubon Society’s 110th annual Christmas Bird Count, the world’s biggest and oldest citizen science project. The data from laypeople help researchers and conservationists study bird trends across North America, Brenzel said.

“The count has been one of the major ways that scientists [can] get a picture of what is happening to birds, ecologies and climate over time,” Brenzel said. “It’s an extraordinary effort undertaken for over a hundred years now by tens of thousands of amateurs spread out across the country.”

The Christmas Bird Count, which began in 1900, began as an alternative to a contest called the Christmas “Side Hunt,” in which Americans would shoot as many birds and small animals as they could during the Christmas season. The first count, organized by ornithologist and National Audubon Society officer Frank Chapman, featured 27 volunteers in 25 locations mainly in the Northeast. Nowadays, 60,000 volunteers count birds between Dec. 14 and Jan. 5 across North America, said Patrick Comins, the director of bird conservation of the Connecticut branch of the National Audubon Society.

Volunteers count birds by their appearance, calls, silhouettes and flight patterns over a period of 24 hours in a 15-mile-diameter circle designated by the National Audubon Society, Barvir said. Each circle is divided according to the number of volunteers available.

There is a “light-hearted” unofficial competition within and between circles to see who counted the most species, Barvir said. In Connecticut, New Haven, Greenwich and other coastal areas tend to have the highest counts due to a larger variety of habitats.

The count has been important in raising the public’s awareness of biodiversity, Comins said.

“The count gets people engaged and connected to nature, and they start seeing the trends themselves,” Comins said.

Because the count is a volunteer effort, the count data — which is released in an annual summary by the National Audubon Society — have limitations, said Yale professor and ornithologist Richard Prum.

“The quality of the data is variable,” Prum said. “But they have documented tremendous changes in American avifauna in the past century.”

Comins said researchers have used the data as evidence for trends such as global warming. Researchers used count data in a National Audubon Society’s 2009 report to show that birds have been shifting their ranges northward for the past 40 years as temperatures increase.

New Haven Bird Club committee chair Chris Loscalzo, who organizes and compiles data from the New Haven Christmas Bird Count, said he has seen many changes in the bird species around New Haven. Loscalzo, who is a clinical instructor at the Yale School of Medicine, used to see hundreds of evening grosbeaks when he began counting birds as a teenager in the 1970s. Now, Loscalzo said, he’s lucky if he sees one or two. On the other hand, some species such as the Carolina Wren, which was rare in Connecticut 20 years ago, is now common in the New Haven area, Loscalzo said.

There were 126 species counted in New Haven for the current bird count.