The Loon Project


The Loon Project is a scientific investigation of the common loon (Gavia immer). Since 1993, we have studied the territorial behavior, reproduction, and habitat selection of this species in Oneida County, northern Wisconsin. We use a simple but powerful approach: capture and individually mark adults and chicks on about 200 lakes that form a natural cluster and examine the behavior of these marked individuals over time. In the past quarter century, we have followed the lives of several hundred loons, many of them for a decade or more. Hence, we have a large sample of longitudinal data that permits robust statistical analysis and provides a rare, life-history perspective. Our study population includes 348 adults that we banded as chicks in the study area. This large sample of individuals followed since hatching gives us the ability to investigate the behavior of young birds — especially how young birds learn about and settle on breeding territories.

A vast popular literature focuses on the common loon, which is both good and bad. On the one hand, much of what this literature says about loons is accurate and has served to satisfy the curiosity of a public eager for information. On the other hand, many books, websites, popular articles, and self-described “loon experts” make pronouncements about loon biology that are simply not true. In most cases, false pronouncements constitute harmless misinformation — the kind of thoughtless blather that Americans are getting more and more used to hearing and ignoring. But trying to sell as facts statements that are not backed up by real data is, at best, reckless. At worst, such misbehavior can hinder the goal we all share of preserving loon populations.

One noteworthy example of false information about loons from a reputable source is the Common Loon page on the Audubon website. Audubon is a great organization that has done a tremendous amount to increase awareness of conservation issues, conserve threatened organisms, and safeguard places on Earth where those organisms can thrive. However, their section on “Nesting” of common loons is riddled with errors. First of all, loons do not “first breed at two years of age”, as they state. Only a small fraction of two year-olds even return to the breeding grounds, as we have shown in a recent publication. Males breed no earlier than age four, and females do not breed until at least age five. Second, it is incorrect to say, as Audubon does, that the yodel call serves as a means to claim a territory. Females claim territories but do not yodel, so this statement clearly excludes female settlements from the outset. And in fact, both males and females claim territories through violent physical battles, not by merely calling. Third, Audubon’s statement that “flying in circles over territory with loud calls” helps in claiming a territory is profoundly false; almost all loons circling above a territory and calling are territorial intruders, not owners. Finally, Audubon has erred badly in their description of courtship that appears in the “Nesting” section. Loon courtship is actually rather quiet; the exuberant courtship display that Audubon describes for loons matches that of the Western Grebe. I hope that Audubon responds to my offer to help them fix their site. In any event, the point is clear; reputable organizations sometimes spread a lot of malarkey about loon biology.

On the Loon Project website, we do not pontificate about all aspects of loon biology, inventing facts to fill in gaps in our knowledge. The findings we describe here are supported by robust statistical analysis, burnished by peer review, and presented in scientific journal articles. To be sure, we sometimes speculate about why loons behave as they do. But when we do, we make it clear that such statements represent hypotheses only. Since we are scientists, not entertainers, we are not afraid to use the very powerful words: “we do not know”.

Despite our cautious approach, 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 have been perplexing, such as the finding that male loons select the nest site. Other findings have been shocking, such as lethal battles for territory ownership, which occur among males only. Certain patterns we have seen in loons, like senescence, are reminiscent of the human condition.

A good deal of our time and energy has focused on learning about the reasons for territorial intrusion in loons. We have learned that intruders seek information about breeding success. Recently, we have come to find out that intruding adults also try to learn about territorial residents, perhaps so that they can plan eviction attempts in the future. One odd fact about territorial intrusions, however, is that a large percentage of them are by neighboring territory owners, rather than adults that lack a territory and are looking for one.

In the past several years, breeding habitat selection by loons has come to be an important topic of investigation for us. We have learned that loons seek to settle to breed on lakes of certain size and pH based on their experience on their natal territories, even though preferences for natal-like lakes sometimes leads them to settle on poor territories. 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.

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, while a bit easier to comprehend, still employ scientific rigor.

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. Things look pretty good for the Wisconsin loon population at the moment. Still, it is comforting each time we see a sight such as the one above in Linda Grenzer’s photo.

Updates from the Loon Project: The LP Blog

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, research activities, 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.