DELMAR, New York (AP) ― The Niagara River corridor from Lake Erie to Lake Ontario is renowned as a spectacular winter haven for hundreds of thousands of water birds. But this year’s bitterly cold season has made it notable for something else: dead ducks.

Biologists say carcasses began piling up by the hundreds in early January after the plunging temperatures started icing over nearly the entire Great Lakes, preventing the ducks from getting to the minnows that are their main source of food. Necropsies on dozens of birds have confirmed the cause: starvation.

“All have empty stomachs. They’re half the weight they should be,” said Connie Adams, a biologist in the state Department of Environmental Conservation’s Buffalo office who has personally seen 950 dead birds.

“This is unprecedented. Biologists who’ve worked here for 35 years have never seen anything like this,” she said. “We’ve seen a decline in tens of thousands in our weekly waterfowl counts.”

It’s a phenomenon that has been seen elsewhere along the Great Lakes, with news reports of diving ducks and other waterfowl turning up dead by the hundreds along the southern part of Lake Michigan. They’ve also been found in Lake St. Clair between Lakes Erie and Huron.

“It’s a hard winter for ducks, like everything else,” said Russ Mason, wildlife director with the Michigan Department of Natural Resources.

Necropsies and toxicity analyses showed many of the Michigan ducks were subsisting on invasive zebra mussels, which caused the birds to have potentially toxic levels of selenium in their bodies, Mason said. Zebra mussels filter toxins from the water and pass them up the food chain.

Most of the dead ducks seen in the upstate New York are red-breasted mergansers, which breed in northern Canada and Alaska and come south for the winter to the Great Lakes region. In most years, there are periods of freezing and thawing, providing enough breaks in the ice for them to dive for minnows.

But this winter, it’s been so bitterly cold for so long that the ice had pushed across 92.2 percent of the Great Lakes’ surface area earlier this month, according to federal monitors, just short of the record 94.7 percent set in 1979.

Biologists say the Niagara River also has ice extending up to 100 yards off shore, creating a shelf where minnows and shiners can hide.

There is evidence some waterfowl gave up and tried to fly farther south but were too weak to do so. Dead birds have been seen along shorelines, on docks and on the ice, their carcasses feasted upon by gulls and bald eagles.

Two weeks ago, Adams said, there were 240,000 water birds in her area’s weekly count.