Black Flies, Fake Nests and Planes!

By Anne Lacy, Crane Research Coordinator

ICF’s Field Ecology Department (FED) staff are continuing their study of nesting Whooping Cranes in central Wisconsin and factors that may lead to nest abandonment by the young cranes. One hypothesis is that biting black flies may be harassing the cranes, to the extent that the birds cannot remain on their nest for the full 30-day incubation period. Following is an account of our spring research involving black flies, insect traps and fake nests, and planes!

Who knew that something so small could be so annoying? We introduce you to the black fly (magnified 45 times), presumed nemesis of the nesting Whooping Crane in Wisconsin (and anyone who likes to be outdoors in May)! These tiny biters come out in force in the spring to get a blood meal so they may develop their eggs.
We’ve set up traps throughout the nesting area in central Wisconsin to monitor the abundance of black flies and other biting insects. Hillary Thompson, a FED intern, hangs a bag of dry ice at each trap in the morning to use as bait for the insects at Necedah National Wildlife Refuge. Black flies are attracted to carbon dioxide (CO2), much like mosquitoes. Dry ice, generously provided by Holiday Wholesale of Wisconsin Dells, Wis. provides the CO2 that brings in the black flies to the traps.
To test what else might draw in black flies to nesting Whooping Cranes, we set up several fake nests.  To simulate a nesting crane, we placed plastic crane models on platforms filled with nesting vegetation and a crane egg (plaster filled) with crane preen oils on it. Both the egg and oil seem to have properties that attract the biting insects. We placed small glue boards on the head of the model and egg for five minutes to get a sample of bugs that are looking for a free meal.
At the same time, we are diligently monitoring real Whooping Cranes that have initiated their nests in and around the Necedah refuge. The most efficient way to do this is by air – and our collaboration with the nonprofit organization LightHawk, an environmental aviation organization that is generously volunteering planes and pilots for daily surveys during the nesting season, allows us to do just that! By flying over the nests every day we can tell if the cranes are sitting tight on their eggs or have left the nest unattended.

View our photo album of the aerial surveys and nesting cranes.