PORTLAND – The Maine Audubon Society has lined up 750 volunteers to participate in Saturday’s 19th annual loon count, a midsummer ritual that provides biologists with a quick snapshot of the state’s loon population.

The survey, conducted on the third Saturday in July, has become a fundamental part of the state’s strategy for protecting its estimated 4,300 birds, the largest loon population in New England.

The loon count also provides Mainers with a chance to give something back to one of their favorite birds, which face threats from shoreline development, lead poisoning and contamination with toxic substances such as mercury.

“People in Maine love their loons,” said Ali Chaney, a wildlife biologist at Maine Audubon. “These are citizen scientists that go out and spend a half-hour of their day counting these loons, and they’re providing us with information we wouldn’t have otherwise.”

Maine, Vermont and New Hampshire are all doing their loon counts on the same day this year. The roughly 300 lakes included in Maine’s count are mostly located south of the east-west line stretching from Rangeley to Calais.

Typical of those who take part in the count is Elwood Beach, who climbs into his canoe a little before 7 a.m. and paddles out into Raymond Pond looking for loons. He takes the south end and a neighbor takes the north end.

“We’ve got a half-hour to look and see how many there are, where they are and whether they’ve got any chicks or not,” Beach said.

Thanks to the loon count, biologists know that the adult loon population has been trending upward in recent years while chick production has remained relatively flat, for reasons no one knows for sure.

Researchers are planning to take a more in-depth look at the data this year to see if they can start finding some answers.

Scientists do know that the largest direct threat to loons in Maine and the rest of New England is poisoning from ingesting lead fishing tackle, followed by trauma caused by collisions with boats and other human contact.

New Hampshire was the first state to ban the use of lead fishing tackle on its lakes. Maine followed suit, but its new law – which went into effect in January – bans only the sale of any lead tackle weighing a half-ounce or less.

Of the 178 dead loons that have been collected by Maine Audubon’s Loon Project since 1987, 50 died from lead poisoning and 38 from blunt trauma.