The Loon Project


During the past 24 years, we have conducted scientific research on the territorial and breeding behavior of common loons (Gavia immer) in northern Wisconsin. Our team has made progress in understanding this species chiefly by means of a simple approach: intensive marking and resighting chicks and adults throughout their lives. Thus, we have accumulated a set of study animals of known age and natal origin.

The Loon Project has produced a wealth of findings. We learned over a decade ago, 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 and are likely to enjoy long lives. 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 were entirely unexpected, 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 the past two years, breeding habitat selection by loons has come to be an important topic of investigation for us. We have learned that loons form preferences for lakes of certain size and pH based on their experience on their natal territories. Such preferences probably help to explain why, once displaced from a territory, loons are often slow to settle on a new one. 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. Nonetheless, recent data, as yet unpublished, suggests that a loon’s preference for the habitat he or she was reared on wanes as it gets older. In other words, a loon’s second breeding territory is less natal-like than its first one.

A lingering question for us relates to the photo at the top of this page: “Why do loons intrude into each others’ territories so often?” We have learned that loons seek information about breeding success. Recently, we have come to find out that loons also try to learn about territorial residents, perhaps so that they can plan eviction attempts in the future. 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 comprehend!

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 published papers and presentations by the Loon Project.

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 since 2003. In the crucial early years of the study, we received funding from the National Geographic Society, the Disney Conservation Fund, Chapman and Cornell Universities…and Mom and Dad.