A trumpeter swan flies over the Lower Wisconsin State Riverway near Blue River in May 2013. The trumpeter swan population has risen sharply in Wisconsin in the past five years, with more than 4,500 of the birds now living in the state. Credit: Mark Hoffman

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Hunted out of existence in Wisconsin decades ago, the trumpeter swan has experienced a sharp surge in population — the latest sign of its stunning renaissance.

The most recent survey found a total of 4,695 trumpeter swans — up from 672 in 2010, according to the state Department of Natural Resources. The survey is the latest sign of success for a species that biologists began reintroducing in the late 1980s after a long absence.

Before the reintroduction, much of the population had been decimated by the late 1880s, and the last recorded sighting in Wisconsin had been in Oconto County in 1937.

Today, populations are also rising in Minnesota and Michigan.

"It's been an unprecedented success across the region," said Sumner Matteson, an avian ecologist with the agency.

The trumpeter swan is the largest native waterfowl in the United States and can weigh more than 25 pounds. Its wingspan is more than 6 feet.

The DNR removed the swan from the endangered and threatened species list in 2009.

Today, they are found in a core area of northwest Wisconsin. There are 25 counties with significant populations. In all, the trumpeter swan can be found in 27 counties, including Racine County. Paul A. Smith, outdoors editor for the Milwaukee Journal Sentinel, described trumpeter swans in a 2012 story as "big and handsome, with a Roman nose and affable demeanor."

The bird's success contrasts with the problems encountered by whooping cranes, another large, high-profile species that has been bedeviled by poor reproduction and other problems.

The trumpeter swan struggled in the early years of reintroduction when biologists experimented with several techniques, including using mute swans to hatch them. The surrogate project was unsuccessful.

One plus for trumpeter swans is that they can breed at the age of 2 — younger than whooping cranes, according to Matteson. Also, they have a larger clutch size and they have never experienced problems with black flies, he said. Black flies have been shown to drive whooping cranes off their nests.

But the biggest factor in the success of trumpeter swans has been in avoiding lead poisoning in numbers that would harm the population.

"We overcame the Achilles heel of restoration efforts, which was lead poisoning," Matteson said.

A trumpeter swan can be killed by swallowing a single lead shot, which remain plentiful in the environment.

It is legal to fish with lead sinkers, although steel sinkers are available. Hunting with lead is allowed for most species and areas, but is prohibited for waterfowl. Only nontoxic shot can be used to hunt ducks and geese.

Some trumpeter swans still die from lead poisoning. Others are killed by illegal shooting and power lines.

Trumpeter swans are counted as part of the DNR's annual spring duck survey.

The agency uses slow-moving aircraft that fly 200 feet above the ground to tally waterfowl.

The count takes place on 66 routes in all corners of the state. Each route is 30 miles long and a quarter-mile wide.

In the latest survey, in May 2015, the agency received funding from the U.S. Fish and Wildlife Service to add 30 routes to count swans — a recognition, Matteson said, that the territory of trumpeter swans is expanding.

The count grew from 672 in 2010 to 3,679 using the 66 traditional routes, or 4,695 using the added routes, according to Matteson, who says more than $1 million in private and public dollars have been spent to bring back the species since 1987.

The results from 2015 were announced this week, in part, because it's tax season. The swan's funding leans heavily on private donations, but is partially paid for with proceeds from endangered species checkoff on the Wisconsin income tax form.

In February, Minnesota officials announced an estimate of 17,000 trumpeter swans. Minnesota ranks first and Wisconsin ranks second among Midwestern states with trumpeter swan populations.

Wisconsin's trumpeter swans originated from eggs plucked from the Alaskan wilds between 1989 and 1997 by Matteson and others. They were then hatched in Wisconsin, including at the Milwaukee County Zoo, using several reintroduction techniques.

Among the first eggs harvested is a female now living in northwestern Wisconsin.

At age 26 (27 in June), No. 82K is the oldest banded swan in North America, Matteson said.