Black Flies Disturbing Nesting Whooping Cranes

There’s more evidence that black flies are making it harder for whooping crane chicks to be hatched in central Wisconsin.

Researchers say the good news is that 20 pairs of whooping cranes nested this spring at the Necedah National Wildlife Refuge. But the bad news is that 17 of the nests were abandoned, leaving humans to gather 19 eggs that were laid, and incubating the remaining fertile eggs at the International Crane Foundation near Baraboo. The researchers say at the time of egg collection, dense clouds of black flies were at the nests. Whooping Crane Eastern Partnership spokeswoman Heather Ray says during the previous two springs, nearby rivers were treated with a natural bacterium that killed flies.

“The suppression treatment really limited the number of black flies pestering the cranes, and we had some successful hatches.”

Ray says the contrast with this year provides more evidence that black flies at Necedah are harming crane reproduction. But she cautions that another factor could be younger adult cranes not being very experienced parents. She hopes many of the crane pairs at Necedah will re-nest this spring and lay more eggs.