Some of the biggest Minnesota duck regulation changes in a generation -- including an early season start and more liberal bag limits for hen mallards and wood ducks -- had a big impact on last fall's hunting season.

"They boosted harvest and hunter numbers,'' as they were designed to do, said Steve Cordts, Department of Natural Resources waterfowl specialist.

The question now is whether wood duck harvest increased too much.

Hunters killed an estimated 621,000 ducks, up 97,000, or 18.5 percent, from 2010, according to U.S. Fish and Wildlife figures released last week. Hunters averaged 8.1 ducks for the season, up from 7.5 ducks in 2010.

"Overall it was a slightly better season than the year before,'' Cordts said.

The more liberal regulations also apparently enticed more hunters to duck blinds: Duck hunters increased 10 percent, from 70,000 in 2010 to 77,000 last fall.

Hunting a week earlier than usual, waterfowlers shot far more early migrant ducks. They bagged 150,000 wood ducks, 92 percent more than the 78,000 killed in 2010. Also a factor: The wood duck daily bag limit, previously two, was increased to three.

Hunters also shot 90,000 blue-winged teal, 143 percent more than the 37,000 killed a year earlier.

The regulation change allowing hunters to kill two hen mallards also appeared to have had an impact: Hunters killed 180,000 mallards, up 30 percent from the previous year, and more of those were hens. They killed 1.4 males for every female shot last fall -- meaning 42 percent (about 76,000) of the mallards killed last fall were hens. The male-to-female ratio was 1.9 in 2010 and 2.0 in 2009.

But the long-term ratio has remained fairly constant, said Todd Arnold, a professor at the University of Minnesota's Department of Fisheries, Wildlife and Conservation Biology who studies mallards. And of the hens killed last fall, just 11,000 were adults, the second-lowest number ever.

"I'm not concerned with what I see,'' Arnold said. "We were shooting 40,000 adult females a year.

"Even with the liberalized regulations, only one of three adult mallards we shoot are hens. We're still giving hens a pass.''

Ten years ago, in 2001, for example, the state's 91,000 duck hunters killed 327,000 mallards, and the male-to-female ratio was 2.2, meaning hunters killed more than 100,000 hens that year.

Arnold's research shows that 50 percent of the mallards shot in Minnesota are raised here.

Despite shooting more hen mallards and nearly doubling the wood duck harvest, Cordts said he doesn't believe hunters hurt those populations. But the state is treading on new ground, too, with wood ducks.

"We don't know exactly what a safe harvest level is [for wood ducks],'' Cordts said. "But we've harvested that many [150,000] in the past,'' when there were more duck hunters.

Minnesota's wood duck harvest hit or exceeded 140,000 seven times since 1975. And Cordts noted the wood duck harvest for the Mississippi Flyway last fall -- 900,000 -- was unchanged from 2010.

But Roger Strand, 76, of New London, a longtime duck hunter, conservationist and member of the Wood Duck Society, is skeptical of the large harvest increase.

"It's concerning to me,'' he said. "We've been urging biologists to continue to be conservative with wood ducks because we can't accurately count them. We shouldn't take it for granted that wood ducks will be able to bounce back. We're going to have to wait and see.''

Cordts acknowledges that wood ducks are difficult to count and that he surveys only 40 percent of the state, but he said the population index has been stable.

Besides opening the season a week earlier than usual, and increasing the hen mallard bag limit from one to two, the DNR also allowed hunters to begin shooting a half-hour before sunrise on the opener instead of 9 a.m. or later, and the state had a split season in the south.

All of those likely factored into the increased harvest, "but I think the biggest change was the early opener,'' Cordts said.

The increased harvest of woodies, mallards and blue-wing teal was, however, somewhat offset by harvest declines for other species.