Biting fly explosion in northern Wisconsin

MILWAUKEE (AP) – Swarms of biting flies are attacking loons in northern Wisconsin this season like never before, causing the birds to abandon their nests in record numbers, according to researchers.

The explosion of the black fly population just as the loons began incubating their eggs has caused more than 80 percent of the loons to abandon their nests in Vilas County and more than 70 percent of nests in Oneida County, according to the wildlife scientists who track the tuxedoed birds with the mournful cries.

A cold spring in Wisconsin and rapid warm up in May caused the black flies to arrive en masse, said Walter Piper, a researcher at the School of Earth and Environmental Sciences at Chapman University in Orange, Calif.

“There’s always a burst that comes out in May. This happens to be one that is particularly devastating,” said Piper, who spends six weeks in Oneida County studying the loons each year.

A species of black flies, Simulium annulus, has a particular attraction to loons, according to research by Michael W. Meyer, of the Wisconsin Department of Natural Resources. His 2012 study published in the Journal of Vector Ecology found the fly species was chemically drawn to the loons.

“It’s one of the most exclusive relationships documented,” Meyer said.

The fly species has always pestered the loons in the past, but this year it was an all-out assault.

“The intensity of the black flies is the worst I’ve seen in the 25 years I’ve monitored loons,” said Meyer, who checks the nests of about 150 loons every two weeks throughout the season in Vilas County.

Research shows about 1,200 loons reside in northern Wisconsin, a population that has been doing reasonably well, Piper said. He estimated the number of loon chicks born this year could be reduced by about 30 percent compared to last year.