Collapse of Midge Population Impacts Mývatn Birdlife

The ubiquitous midge is almost completely absent from Mývatn, the pointedly named ‘Midge Lake,’ this year. But while many people might celebrate the scarcity of the thick clouds of blackflies that generally characterize the region, RÚV reports that the population collapse, which happens on a cycle of six to nine years, will have a long-lasting impact on local birdlife.

In a normal season, there are as many as 100,000 hatchlings around Mývatn, says Árni Einarsson, director of the Mývatn Research Station. But this year, there are just under 1,000.

Mývatn, photographed by Bernello, CC 3.0

Midges are a vital food source for birds around the lake, but there are almost none now, Árni reports. As a direct result, “we’re not seeing any chicks on the lake,” he explained. “There are 20,000 pairs of ducks, but very few are raising any young. They’ve largely neglected their nests and stopped laying. Have abandoned their eggs, left them behind in the nests. And so those chicks that do hatch only live a few days.”

Árni estimates that the midge population has decreased by ten thousandfold this year. The drastic drop in midges can be attributed to fluctuations in Mývatn wherein midges devour all their food sources at the bottom of the lake. “The food on the lake bed runs out and then the midge population collapses and then the fish come and finish off whatever remains of them […] and there are no midges left.”

Árni says this happens every seven to nine years—it’s now been about eight since the last time the midge population collapsed. As a result, the bird population will be much smaller for the next two to three years. “This makes a dent in the stock,” he concluded. “It doesn’t renew itself.”

Sink Or Swim

Biologist Jóhannes Sturlaugsson in Þingvallavatn with brown trout

“Some things in nature naturally inspire an emotional response. The Þingvallavatn lake brown trout is one of these phenomena. It’s a fantastical, mythical creature,” says biologist Jóhannes Sturlaugsson. For the last two decades, he has studied the brown trout stock in the lake, unique in Iceland and even the world. Trout numbers in the lake are up, after years of decline. That’s good news, but the same can’t be said for another of Jóhannes’ research subjects: wild salmon, currently under threat.

This content is only visible under subscription. Subscribe here or log in.

Continue reading