Fewer loon chicks surviving because of climate change, researchers say

Still, Johnson said he thinks Piper’s findings are “concerning.”

Piper heard and saw his first loon in the north woods as a child. “I was in Ontario on a lake,” Piper recalled. “I was underneath my warm Hudson Bay blanket and in our primitive cabin on the lake shore and heard this ethereal, haunting sound coming across the lake.”

Piper began researching loons in 1993 focusing on territory defense, habitat selection and breeding behavior in three counties in Wisconsin. He nets and weighs adults and chicks, and fits them with leg bands for identification.

“Over the years, I started to realize that the chicks weren’t as heavy as they used to be at a certain age, and sometimes only one chick instead of two would survive,” Piper said.

His data showed that the total weight of chicks four to five weeks old had decreased by 11% over the last quarter century. “That equates to more chick mortality. I had to explore this and find out what’s going on.”

Piper worked with Max Glines and Kevin Rose, water clarity specialists from Rensselaer Polytechnic Institute in Troy, New York, who co-authored the study published in Ecology. They gathered data from the lakes where the loons he studied were breeding. They discovered water quality had declined at the same time rainfall had increased.

“That link between rainfall and water clarity is quite strong,” Piper said. “We can clearly point to rainfall as the culprit. Heavy rains especially in July when adults are feeding chicks, make the water cloudy, making it more difficult for parents to see their prey. … The chicks really suffer,” Piper said. “The parents cannot find enough food.”

Piper began similar studies in Minnesota in 2021. He also will work with colleagues to find out what kind of substances rainfall is bringing into the lakes.

“We haven’t nailed down exactly what it is that’s washing into the lakes that make them less clear,” he said. “It could be fertilizer, pet waste or something else. We have to get to the bottom of this.”

His loon conservation work has also shown that loons abandon their nests when harassed by black flies. Black fly populations have increased in the past few decades in Wisconsin, he said. Their population is boosted by more rain.

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