Historically, our work has focused on the behavioral ecology of loons, centering on territorial behavior. However, our discovery in 2019 that the Wisconsin loon population is declining has reshuffled our priorities. Now we have begun to focus our attention on 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 improve our efforts to discern causes of population fluctuations.
While the population study must take center stage, our work on the behavioral ecology continues. Recently, we have made important findings along five major axes: 1) the impact of age — in particular, old age — on behavior and survival, 2) habitat preferences, such as the preference of loons hatched on small lakes to settle on small lakes, which contain less food and produce fewer chicks than large ones, 3) nesting and chick-rearing behavior, 4) vocal behavior, especially the male-only territorial yodel, used to keep territorial intruders at bay, and 5) differences in tameness (tendency to dive at a certain distance when approached by canoe) among individuals. These research avenues will continue, insofar as they are compatible with our population work. Several prongs of our ongoing research are described below.
At present, we are exploring the impact of age on reproductive and aggressive behavior of loons and have recently described a striking system of terminal investment in males. We have begun to explore possible proximate causes (hormones, parasites, telomeres) of loss in condition with age.
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.
About 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 do 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. It seems virtually certain that yodels change in specific ways with age and that flying intruders respond differently to yodels from young and old territory owners. Several exciting playback experiments are possible in the loon system.
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 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.