“We’re cautiously optimistic after seeing two years of growing chick numbers,” said Maine Audubon wildlife ecologist Tracy Hart. “But it will take several more years before we know if that is a real upward trend, or just two really good years.”

Maine lawmakers have attempted to grow the population of the loons with bans on lead fishing tackle that the birds sometimes accidentally swallow. Laws that limit boat speeds have also helped because they prevent boat wakes from washing out nests, conservation groups say.

It’s still too early to know if Maine’s loons are on a sustainable path to recovery, and the success of the state’s breeding loons is critical to the population at large, Hart said. Maine has thousands more loons than the other New England states, with the other five states combining for about 1,000 adults. The state is home to one of the largest populations of loons in the U.S., which has about 27,000 breeding adults in total.

Minnesota has the most loons in the lower 48 states, with a fairly stable population of about 12,000 adults, but they are in decline in some parts of their range.

While loons are not listed under the U.S. Endangered Species Act, they are considered threatened by some states, including New Hampshire and Michigan. The U.S. Forest Service also considers the common loon a sensitive species.

The birds migrate to the ocean in late fall and need a long runway to take off, meaning winter can be a treacherous time for the birds because they get trapped by ice in the lakes and ponds where they breed, said Barb Haney, executive director of Avian Haven, a wildlife rehabilitation center in Freedom, Maine.

“We’re getting a lot of calls about loons that are iced in,” Haney said, adding that the center was tending to one such patient this week.