Loons in the Upper Midwest have just survived a worse-than-average year for black flies. “Worse-than-average” might not be the way to put it. In a reverse Lake Wobegon scenario, worse-than-average black fly years are the new normal in Wisconsin and Minnesota. Nowadays, we know black flies will be awful; we only wonder how awful.

Researchers who venture close to a loon nest abandoned to flies get a small taste of the agony these insects inflict. As if moved by a sweeping dipteran consensus, a cloud of flies buzzing about a nest — drawn by warmth, movement, and carbon dioxide— suddenly shifts its attention to approaching humans. The flies alight on your head and neck, crawl underneath your jacket, and fly errantly into your nose, ears, and mouth. The experience is unpleasant and alarming. It is difficult not to scream.

Yet the tactile and chemical cues humans produce are not satisfying to black flies. They crawl and buzz and annoy. But they do not bite us. So we cannot say that we truly know how loons feel when they are besieged by black flies — when the mouthparts of hundreds of females are inserted into their head and neck at once and departing flies are quickly replaced by new ones that have been waiting their turn to feed. And when it lasts for hours. That helpless miserable sensation is one that humans can only imagine.

Despite the misery they cause, black flies have one great virtue. They plague incubating loons for only a few short weeks.

In the past seven to ten days, black fly numbers at loon nests have dropped substantially. You do not need me to tell you this; the loons have weighed in. Two weeks ago our marked loons in Minnesota and Wisconsin rested and foraged near their nests, gazed longingly at their nests, circled around their nests, and — on a few occasions when we ventured too close — defended their nests from us. This past week has been different; loons are ON their nests. Thus, after a stuttering start, the breeding season has begun.