The Study
The Loon Project is a long-term scientific investigation of territoriality, breeding ecology, and population dynamics of common loons in the Upper Midwest. We have two study populations: 105 marked breeding pairs in northern Wisconsin (chiefly Oneida County) and 110 marked pairs north-central Minnesota (Crow Wing and Cass counties). We have published 35 scientific articles on loon behavior, ecology and conservation.
Who We Are
The project is directed by Walter Piper of Chapman University in Orange, California. I grew up in Cleveland and Houston, but my family spent summers on Squam Lake in New Hampshire and on Lake Temagami, in central Ontario. On those two lakes I heard and saw loons. Like many folks, I was instantly enchanted. I began to mark and study loons in Oneida County, Wisconsin in 1993. I have never looked back.
I have worked with a dedicated team of collaborators, supporters, friends over the years. Without these folks — especially the kind people of northern Wisconsin and Minnesota who share my passion for loons and strive to help them any way they can — my work would be impossible. The unsung heroes of the project are student research assistants, who work many lonely hours collecting data on loons, usually as a means to get field experience in preparation for a career in animal behavior, ecology, or wildlife biology.
Could Loons Disappear from the Upper Midwest?
It is difficult to imagine spending time on northern lakes without hearing the calls of loons. Yet a recent study projected that the breeding range of the common loon will shift hundreds of miles northwards in coming decades. If so, folks living in Minnesota and Wisconsin would have to drive north to Canada to see loons.
What do we know about the current loon populations of Minnesota and Wisconsin? Comprehensive statewide data come from Breeding Bird Surveys*, which have been conducted by expert birders on fixed routes across North American since 1967. These data (see below) show that loon populations were on an upswing from 1967 until about 2010 in both states, but have been falling sharply in the past decade and a half.
Why Our Work Matters
The data collected by the Loon Project in northern Wisconsin since 1993 echo the pattern above; breeding success and population size rose in the late 1990s and early 2000s but are now in sharp decline. In Minnesota, we have more limited data, yet there are three indications of decline. Body condition of Minnesota adults has begun to decrease, in parallel with Wisconsin. Chick production in Minnesota is on a downwards trajectory. Perhaps most alarming, the adult survival rate in Minnesota is lower than in Wisconsin.
These findings suggest that poor reproduction is at the heart of the Upper Midwest loon decline, but we cannot yet point to a specific cause or causes. Understanding the specific causes of the downturn is essential if we wish to conserve loons in the region. That is our goal.
The Wisconsin Loon Project
Studying a known-age population in Wisconsin has allowed us to learn how a loon’s survival and breeding success changes as it ages. From a conservation standpoint, the high resolution of our data has made it possible to produce a much clearer picture of population dynamics in northern Wisconsin than is possible in the rest of the loon’s breeding range.
Loons Are in Trouble in Wisconsin!
In 2019, we reported warning signs related to the survival and breeding success of loons in northern Wisconsin. In findings that echoed what other surveys have detected statewide (see above), we showed that the loon population in northern Wisconsin has declined overall by 22% during the past quarter century. Wisconsin loon pairs are producing fewer chicks; chicks are growing more slowly; and chicks are dying at much higher rates now than 30 years ago, when our work began. A population projection suggests, moreover, that the northern Wisconsin loon population is shrinking by as much as 6% each year. This is an alarming estimate but is roughly consistent with the BBS data above. If these findings are accurate, we will see noticeably fewer loons on northern Wisconsin lakes within the next five to ten years.
A troubling dimension to the Wisconsin decline is that it is most pronounced among young adults that have returned to the breeding grounds to look for territories but have not yet settled. This means that much of the decline takes place not among the breeding pairs that we watch for many hours out on the lake but among the furtive, skulking individuals that wander widely in search of breeding vacancies. Recent findings suggest that many young adults received insufficient food as chicks, a pattern that is linked to lower survival and breeding success during adulthood. Since we have also recently learned that declining water clarity is, at least in part, responsible for poor feeding conditions, a picture is beginning to emerge of how and why the population in Wisconsin is declining.
Our goal at present is to probe the decline further, by determining the precise cause of declining water clarity. If, for example, the loss of clarity results from use of leeching of fertilizer and other nutrients into lakes from lakeside lawns, we will be able to make recommendations about steps to take that might reverse the decline.
The Minnesota Loon Project
In 2021 we expanded the Loon Project to establish a second loon study population in north-central Minnesota near the town of Crosslake. We now have 82 of 105 focal pairs marked. The Loon Project team has begun to collect data on annual survival rate, nesting success, and causes of nesting failure in Crow Wing and Cass counties, just as we have done in Wisconsin.
We have an important new finding after our 2025 field season. As a result of extensive marking of Minnesota chicks from 2021 through 2025, we have had two “crops” of juveniles begin to return as young adults and begin to look for territories. These 2-, 3-, and 4-year-olds do not yet have territories; they are present as “floaters” who intrude into territories and live itinerant lives on parts of lakes not defended by territorial pairs. Nonetheless we detect these young nonterritorial birds routinely during our research activities. Returns of these young birds allow us to produce an estimate of the survival rate of young adults. After two solid years of observation and detection of these youngsters, we can see a strong parallel between our Minnesota and Wisconsin study populations. In short, the very low survival rate of young adult loons, which is the alarming hallmark of the Wisconsin population decline, is present in the Minnesota population as well. This is another good indication that the loon population of Minnesota, like that in Wisconsin, is in decline — at least in our study area in Crow Wing/Cass Counties.
Now that we have confirmation that Minnesota and Wisconsin loon populations are both in decline owing to very low young adult survival, we can target our research efforts a bit more narrowly. Our main focus, at present, is to learn whether loss of water clarity in Minnesota is harming loon chicks, as we have found recently in Wisconsin. Linking loss of lake clarity to the population downturn in both states would place a spotlight on improvement of water clarity as a means to turn the broader decline around.
Updates from the Loon Project: The LP Blog
The Loon Project is ongoing, and we make new findings all the time. Our blog enables us to describe recent findings, activities, and accomplishments for folks who are interested. Check out “LP Blog” for the most up-to-date information. If you are really gung ho, sign up to “follow” the blog and receive an e-mail each time I add a new post. During the breeding season (May to August), I provide frequent updates of what we are seeing in the field — nests, chicks, breeding success rates and conservation-related findings. At all times of year, I share information about published papers and presentations by the Loon Project.
Funding
The National Science Foundation provided funding for our work from 2003 through 2018. Between 2021 and 2022, the National Loon Center provided substantial funds to support our work. However, we have no major source of funding for Minnesota or Wisconsin for 2026 and afterwards. With federal funding sources suddenly uncertain in the United States, we are finding it harder and harder to keep the project on track. If you share our commitment to learning what is ailing loons in Wisconsin and Minnesota and would like to help us work towards turning the Upper Midwest decline around, please consider a donation to support our work.
* Citation for these data: Hostetler, J.A., Sauer, J.R., Hines, J.E., Ziolkowski, D., and Lutmerding, M., 2023, The North American Breeding Bird Survey, Analysis Results 1966 – 2022: U.S. Geological Survey data release, https://doi.org/10.5066/P9IU1UZ6.