At a March meeting of loon researchers in New Hampshire, John Cooley of the Loon Preservation Committee showed that the recent increase in severe rainstorms in the Northeast has made flooding of loon nests a routine cause of nest failure there. John’s report was eye-opening to me for two reasons. First, nest floodings occur seldom among Upper Midwest loons, so his result showed that environmental threats facing loon populations vary regionally. Second, and more important, John’s findings pushed me past a personal cognitive tipping point. I now see clearly that climate change, which has negatively impacted plants and animals worldwide, has not spared the common loon.*

I must admit that I was among those who hoped that loons might dodge climate change. I have long understood that hundreds of terrestrial birds are being adversely affected by changing patterns of temperature and rainfall. But loons are aquatic, I reasoned. Maybe they are different.

In fact, the list of climate-related factors known to harm loons is growing. In addition to the new flooding threat from storms that John’s talk revealed, the list includes black flies, which are getting worse owing to increasing annual rainfall. And our just-published paper shows yet a third problem that rainfall poses for breeding loons. In a nutshell, July rainfall reduces water clarity, which hinders loons’ efforts to capture fish to feed their chicks. This problem has led to a decline in chick mass and increase in chick mortality over the past 25 years in northern Wisconsin. If you are keeping score, we now know of two climate-related patterns that reduce hatching success of loon eggs and one that increases mortality of chicks after hatching. It is no wonder that loon reproductive success is falling across most of the breeding range, including its heart, in Canada.

These are not short-term patterns likely to reverse themselves in a year or two. Flooding, black flies, and water clarity have been getting worse for at least 25 years. No rational person who has seen these data and is capable of looking at the world with an objective eye can doubt that climate change is harming loon populations.

What now? Do we resign ourselves to loon population decline in the Upper Midwest? Do we accept the models that show the breeding range shrinking northwards until the species no longer breeds in the United States by 2050 or a bit later? Do we sit down with our children and grandchildren and explain to them that they will have to go to Canada to see the birds whose charismatic presence near our summer homes has so enriched our lives? I don’t think so. We cannot reverse climate change in a hurry. We cannot stop rain from falling. But continued field research might allow us to pinpoint climate-related hazards faced by loons — such as the precise identity of the material that rain is washing into lakes to reduce water clarity — and use that information to mitigate the harmful effects of climate change. The current picture is disheartening, but we must do what we can to save loons.

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*Featured photo by Linda Grenzer on April 8. Loons, mostly males, have begun to trickle back to the Northwoods. Linda took this photo of the male that has bred for 12 years on Deer Lake in Lincoln County. But here he is exploring nearby Muskellunge Lake, to which the longtime male resident did not return in 2023. It will be interesting to see if he settles on Deer Lake, where he has experienced seven nest failures in a row, or moves over to Muskellunge, which has a very good track record of chick production.