For the past 20 years, Maine’s population of common loons has sluggishly increased, while loon chick populations have fluctuated.

But, according to the results of this summer’s yearly Maine Audubon loon count, adult numbers appear to have peaked. Loon chick populations declined for the second consecutive year, sparking further concern.

“It doesn’t signal disaster, but we need to get a handle on it,” said Susan Gallo, Maine Audubon wildlife biologist and loon count director. “Our results indicate that the adult loon population’s slow-but-steady growth over two decades seems to have ended, and that the population has potentially hit a plateau.”

For the third year in a row, Maine Audubon has received an estimate of about 2,500 adult loons from volunteer monitors.

Results from the 2003 one-day count in July estimate a population of 2,558 adult loons and 208 chicks on 328 lakes and ponds in the southern half of the state, south of the 45th parallel. This includes water bodies to the south of Rangeley and Calais.

Although the count takes place statewide, the estimate is limited to the southern part of the state because there are enough loon-counter volunteers in that area to cover a representative sample of Maine’s lakes, Gallo said.

This year’s count in July revealed a decline in the population of loon chicks for the second year in a row, but that two-year drop follows three years of steady increases, Gallo said.

“Because the loon chick population increased in the immediate three years before the last two years of decrease, there may be no cause for concern,” she added.

But the numbers of adult loons will not reflect a decline in the size of the chick population for several years.

“Loons don’t even begin to nest until they’re about seven years old, and even then, they lay only one or two eggs a year. So if loon chick numbers are in fact declining, there will be quite a lag before we see an effect on the adult population,” she said.

Although Maine boasts the largest population of loons in New England, shoreline development, high levels of mercury and other toxins, lead sinkers and boats all pose potential problems to breeding loons and their chicks.

“Maine Audubon has long worked to promote awareness of the impact of people on loons, most recently with a brochure and poster titled, ‘Living in Loon Territory,'” Gallo said.

The publication highlights action that homeowners, boaters and anglers can take to reduce any adverse impacts. The ingestion of lead sinkers used in fishing continues to be a problem for common loons, even though a ban on the sale of lead sinkers weighing a half-ounce or less was passed by the Maine Legislature in 2000, she added.

Maine Audubon has applied for grant money from the Maine Outdoor Heritage Fund to get volunteers involved in monitoring loons earlier in the year and to make weekly assessments of loons.

“We need to ramp up our survey work,” Gallo said.

Maine Audubon hopes to determine the size of Maine’s breeding loon population, its productivity and differentiate between breeding adults and nonbreeding adults.

“Slow growth over the last 20 years could be the result of rogue or nonbreeding loons not breeding successfully. Another scenario could be that breeding is leveling off. We also need to learn how often people see loons together in pairs or in large groups,” Gallo said.

When loons are not breeding, they often congregate in large groups known as “rafts.”

“They’re really quite social. We’ve had group sizes ranging from 10 to 15 and even as many as 100, as was seen on Sebago Lake last year,” she added.

tkarkos@sunjournal.com

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