Historically, our work has focused on the behavioral ecology of loons, specifically territorial behavior. However, our discovery in 2020 that the Wisconsin loon population is declining has reshuffled our priorities. We have now turned our attention to that decline and its possible causes. Fortunately, our expansion into Minnesota through our partnership with the National Loon Center has allowed us to establish a second study population 200 miles west of the traditional one in Wisconsin. Not only will marking and ecological study of Minnesota loons allow us to describe the population dynamics of loons in that state, it will also allow comparisons across different regions of the Upper Midwest in order to help us learn causes of population fluctuations.
Several prongs of our ongoing research are described below. While our efforts to learn about causes of loon population decline in Wisconsin (and likely Minnesota) are now front and center, we are moving ahead with studies of loon behavior and ecology as well.
We are looking at factors that predict success at hatching and fledging loon chicks. That is, do old or experienced females enjoy higher hatching success than young and inexperienced ones? Does the number of years a pair has been together make a difference? And how are lake size, lake pH, and water clarity related to breeding outcomes (if at all)? Of course, our results will shed light on the nesting ecology and life histories of loons, which are interesting to ponder. But they will have important conservation ramifications as well. Preliminary results suggest that both males and females enjoy better breeding success once they have been on a territory for a few years, and that males continue to get a little bit better at breeding each year for at least 20 years! This tells us that, in trying to conserve loon populations, we must try to protect the lives of experienced adult breeders, not just the lake habitats they use for nesting.
At present, we are collaborating with a molecular biologist and colleague at Chapman to examine whether telomeres (end caps of chromosomes that shorten throughout life) might be useful for estimating age in adults that we capture and mark for the first time and whose ages and life histories are a mystery. Preliminary results are promising! Marco Bisoffi, our colleague, has measured loon telomeres in many Wisconsin loons of known age and determined that telomere length is a rather good indicator of age. this finding raises the prospect that we might measure the telomeres in our new Minnesota study population as a means to estimate age. This breakthrough, if it holds up, will greatly enhance our knowledge of the age structure of the Minnesota study population and therefore improve the population model we will develop in the next few years.
Another collaboration — this one with researchers at Rensselaer Polytechnic Institute in upstate New York — has begun to suggest that part of the cause of the Wisconsin loon population decline might be a decline in water clarity. It is early days, but northern Wisconsin lakes have become less clear in the past decade or so and adult loon masses — especially those of males and chicks — have declined in concert with water clarity. We do not know the reason for the recent shift in clarity, but it is likely to have increasingly dire consequences for loons, if it continues.
Having established that natal habitat preference is very strong in this species, we have begun to look at the possibility that small lakes are ecological traps and also to investigate the opposite possibility — that there are benefits for adults breeding on small lakes that might offset the obvious disadvantages.
A decade ago, we made the startling discovery that male loons choose the site where eggs are laid. This finding has profound consequences for male and female territorial behavior. In particular, we should not be surprised that male loons fight much harder than females to hold their territories. They do so, in part, because a male that loses his territory loses also his accumulated knowledge of where eggs can be placed in order to avoid feeding raccoons! Most recently, we also showed that black flies (Simuliidae) attack loons so mercilessly that they cause widespread nest abandonment in some years.
An unexplored avenue for research on our project is the vocal behavior of males and how it relates to male senescence. Males signal identity, size, and body condition with their territorial yodel and increase their rate of yodelling as they age. An exciting finding made by Brian Hoover, a postdoc on the project, is that the pitch of the yodel call rises as a male ages. In other words, old males have high-pitched yodels; young males have low-pitched yodels. We are scratching our heads over a puzzling — but very clear and strong — finding.
Some of our adults allow approach to within a few meters without alarm, while others begin to dive and avoid us at 50 meters. We have just begun to measure such tameness with laser rangefinders and have learned already that tameness is consistent within individuals, highly correlated between pair members, and similar between parents and offspring (i.e. probably heritable). We are currently trying to determine whether tameness of loons matches the degree of human recreational activity on their breeding lake and see if tameness provides a fitness benefit.
We welcome inquiries from potential collaborators with interest and expertise that match one or more of these goals. Chapman University supports postdoctoral fellowships each year through the Grand Challenges Initiative, which provides training in instruction as well as collaborative research opportunities with faculty. There are numerous opportunities for Chapman GCI postdocs to work with the Loon Project.