The Loon Project


We conduct scientific research on a marked study population of common loons (Gavia immer) in northern Wisconsin. During 22 years of field work, we have learned a good deal about the territorial and breeding behavior of this species. Our research has shown, for example, that loons breed in socially and genetically monogamous pairs and that, contrary to popular opinion, loons do not mate for life. Yet both members of a breeding pair do tend to return year after year to the same small lake or portion of a large lake. So lake residents are often correct when they hear a loon call in early May and remark, “The loons are back!”.

Some of our results are puzzling, such as the finding that male loons select the nest site. Yet that discovery helped us understand another peculiar pattern that we had noted: lethal battles for territory ownership among males only. Males’ ability to control nest location gives them a greater stake in remaining on a familiar territory, it seems, because they can learn to avoid poor nesting sites by trial and error and greatly increase their nesting efficiency.

In recent years, breeding habitat selection by loons has come to be a focal issue for the Loon Project. We have learned that loons form preferences for lakes of certain size, clarity and pH based on their experience on their natal and first breeding lakes. These startling insights probably help to explain why, once displaced from a territory, loons are often slow to settle on a new one. They are picky about breeding lakes! The tendency for individual loons to form specific habitat preferences also has important implications for efforts to reestablish extirpated populations in regions south of the current breeding range.

One of the lingering questions that we have not yet fully answered relates to the photo at the top of this page: “Why do loons intrude into each others’ territories so often?” We have learned bits and pieces. Recently, we have made more advances. But we have not solved the puzzle to our satisfaction. One odd fact about territorial intrusions is that a large percentage of them are by neighboring territory owners, rather than adults that lack a territory and are looking for one.

We invite you to examine these findings and many others related to loon territorial behavior, habitat settlement and reproduction under “Findings“. We have provided links to scientific papers there, but you can also look at our popular articles, which are a bit easier to read.

Study of The Loon Population

One benefit of our behavioral research is that it allows us to monitor the loon population in northern Wisconsin using a large sample of marked individuals. In the course of our study, we have measured both adult and juvenile survival and produced a robust estimate of population stability. Look under “Findings” > “How healthy is the loon population in northern Wisconsin?” for more information and copies of our published papers related to population dynamics.


The Loon Project is ongoing. This site 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, territorial battles and so forth. At all times of year, I will let you know about papers that we are publishing and presentations we have made.

Loon Video!

We make available here video that shows what our leg-banded loons look like (under “Why Band Loons?”). In addition, if you look under “Findings” > “How does a loon acquire a territory?”, you can watch a couple of vicious battles between loons for ownership of a territory.

Who We Are

The project is directed by Walter Piper of Chapman University in Orange, California. But I have had academic and field assistance from numerous collaborators over the years and support from many lake residents, who let us view loons on their lakes. The unsung heroes of the project are research assistants, who work countless 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. Many research assistants take on side projects that allow them to devise a new means of data collection or an experiment, which can be written up for presentation or even publication after the season. To find out more about the people on the study, look under People.


The National Science Foundation has provided funding for our work over the past 10 years. Prior to 2003, we received funding from the National Geographic Society, Disney Conservation Fund, Chapman and Cornell Universities…and Mom and Dad.


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