RANGELEY – Tony Marcellino watched a mother duck and three of its ducklings parade past his home on Rangeley Lake Wednesday afternoon.

But he’ll be watching for loons, not ducks, this weekend when he joins about 60 volunteers from 7 to 7:30 p.m. on Saturday, July 17, for Maine Audubon’s 21st annual statewide loon count.

Marcellino, 71, a retired engineer, is a volunteer loon counter and regional coordinator for the Rangeley area, a coverage district that includes 30 ponds and lakes in northwestern Oxford and Franklin counties.

“But we can only cover about 14 to 15 of them, because some ponds aren’t easily accessed,” Marcellino said.

Marcellino and his volunteers will be part of a group of more than 1,000 “citizen scientists” who are tasked with recording a half-hour snapshot of Maine’s loon population, said Maine Audubon spokeswoman Marie Malin.

Biologists are especially interested in the results of this year’s loon count, because growth of the adult population has appeared to have halted in the last three years, said Susan Gallo, a Maine Audubon wildlife biologist and director of the organization’s Maine Loon Project.

“After a slow but steady population growth over 17 years, we’re concerned about the recent plateau,” Gallo stated in a press release.

At 4,300 adults, Maine’s loon population is the largest in New England, according to Maine Audubon.

However, Gallo states, Maine’s loons suffer from extremely low productivity compared to neighboring states.

Shoreline development, high levels of mercury and other toxins, lead sinkers and boats all pose problems to breeding loons and their chicks, Malin added.

Marcellino said his region’s loon counts have been “pretty consistent.” “They’re not decreasing in chicks, but then they’re not increasing in chicks either. We see between six, eight and 10 chicks each year,” he added.

He attributed the scarcity of young loons to increased development, noise, boats and construction in and around water bodies.

“On Big and Little Kennebago lakes and Upper and Lower Richardson lakes, we might get a count of 19 loons and two or three chicks. But on Rangeley Lake, we’d get 26 loons and no chicks, because, I believe, there are less places for loons to nest now,” Marcellino said.

Despite the scarcity of loon chicks for the second year in a row, Gallo says that historically, loon chick numbers rebound after two or three years of decline.

A keystone of Maine Audubon’s loon project, the annual count was launched in 1983 as part of a joint effort by the organization and the Maine Department of Inland Fisheries and Wildlife to assess Maine’s common loon population.

At the time, Malin said, many people believed they were observing fewer loons than they did in past years, but no data existed then to show whether the population was actually declining.

“Today, thanks to the help of hundreds of volunteers statewide, biologists have a good estimate of Maine’s loon population, which until recently has appeared to slightly increase,” she added.

Maine Audubon is no longer accepting volunteers for this year’s count, but those who would like to participate in 2005 may contact Gallo at 781-2330, extension 216.