MINNEAPOLIS — Wildlife managers in the upper Midwest expect the first results next week from tests that could provide an early warning on whether ducks flying south for the winter are carrying the deadly kind of bird flu that devastated the region’s poultry earlier this year.

Minnesota Department of Natural Resources staffers were in the field last weekend for the opening of waterfowl season, collecting about 500 samples from ducks shot by hunters. That put them more than halfway to their goal of 800 — said Lou Cornicelli, the DNR’s wildlife research manager.

Those samples will be tested at the National Wildlife Health Center in Madison, Wisconsin, for highly pathogenic bird flu viruses such as H5N2. It’s part of a nationwide surveillance plan, because officials fear that migrating waterfowl could carry avian influenza to major poultry-producing states in the South and East that escaped the disease earlier this year, as well as back to the Midwest.

Scientists believe that wild birds, primarily ducks, are the main reservoir of the H5N2 and other bird flu viruses that began showing up in North America last November. Wild waterfowl don’t normally get sick from them, but the viruses kill domestic poultry flocks quickly. Bird flu cost producers more than 48 million chickens and turkeys — the majority in Iowa and Minnesota — before it retreated with the onset of warm weather in June.

Local and federal officials in other northern states where waterfowl seasons opened last weekend also collected samples from ducks, said Hon Ip, a microbiologist with the center. He said determining whether these ducks are carrying bird flu viruses is critical.

“We are kind of now edging into the beginning of the major migratory period. … This is really the first opportunity we as a country will be able to get a significant number of samples,” Ip said.

The ducks will fill in data gaps, officials said, because H5 viruses have been found in only about 100 wild birds across the U.S. since December, and only two in Minnesota.

Hunter cooperation was overwhelmingly positive, Cornicelli said. DNR field staffers went to hunting spots in seven Minnesota counties, including Kandiyohi and Stearns, where turkey producers were hit hard.

Staffers will take swabs for a few more weeks until they reach their goal, Cornicelli said. Most ducks sampled last weekend were from the area or early migrants, he said, so samples taken later will include species that migrate later or start from farther north, giving researchers a broader mix.

In a commentary published Monday in Virology Journal, U.S. Geological Survey scientists said active surveillance of live birds appears to offer the best chance for determining the true distribution of H5 viruses. They proposed putting a higher priority on waterfowl near poultry farms — as well as look more closely at rodents, insects and other species in those areas that could carry the virus into barns.

Cornicelli said the article pointed out the need for stronger surveillance but didn’t say how to pay for it.

“This surveillance stuff is really expensive,” he said.