The Trials and Tribulations of Accomplished Loons

It is hard being successful. I don’t know this from personal experience, of course, but I have studied the topic in some detail. In fact, I spend a disproportionate amount of my time analyzing the behavior and ecology of highly accomplished loons.

You see, the individuals that I talk about in my blog and focus on in my scientific papers are the crème de la crème among loons. These animals have passed myriad biological milestones. They have hatched from eggs, survived the cold and dangerous first few weeks of life, dodged eagles and loon intruders to reach adult size at four months of age, completed energetically-costly molts, and navigated through thousand-mile migrations to and from the ocean. Above all, though, the subjects of my research effort have won battles to claim and defend breeding lakes, found safe nesting locations, and reared healthy chicks. Those chicks — their life’s work — permit my team to capture and mark them for study.

Don’t get me wrong; I did not set out 24 years ago to study this elite class of loons. In fact, I have always been most interested to learn how young adults without territories collect information about potential breeding sites and decide where to settle. But it is difficult to study such “floaters”, because, being floaters, they bounce around. Moreover, floaters cannot be captured easily, because they do not have chicks to protect. Only two years ago did we accumulate enough information to assemble a scientific paper that describes the goals and strategies of this itinerant cohort of individuals.

We are mostly stuck investigating the lives of life’s winners, like “Honey”, the breeding female on Muskellunge Lake whom Linda Grenzer has immortalized in countless photos (see the recent one above). I am not really complaining. We have learned a good deal about the lives of loons in general, despite focusing on the loon elite. Even winners face adversity and evolve interesting strategies to cope with it.

Jeremy Spool, a Ph.D. student at U.W.-Madison who works with Lauren Riters, developed an interesting research question aimed at the coping mechanisms of winners in our study population. Jeremy asked an intuitive, reasonable question about territorial breeders. Territorial pairs, Jeremy thought, should defend their lakes in a way that reflected their recent success. Pairs that had produced chicks in the past few years should be aggressive in territorial defense, because they were defending a resource whose value was clear and which would be costly to lose. Pairs that had not been successful rearing chicks recently might be expected to be a bit more lackadaisical about territory defense. Jeremy tested his hypothesis by exposing some of our territorial pairs to a loon decoy, which simulated a territorial intruder, and measuring their behavioral responses.

Jeremy’s results were unexpected. Pairs with recent breeding success did not behave more aggressively toward the decoy than unsuccessful pairs. In fact, they showed less aggressiveness towards intruders than did failed pairs. But successful pairs were clever about their defense; they became aggressive towards intruders in the few days leading up to egg-laying, a period when territories become vulnerable to intruders owing to incubation. In contrast, pairs without chicks the previous year showed no change in level of aggressiveness during the season. Jeremy concluded that successful pairs save energy by becoming aggressive only when they need to.

What Jeremy’s findings appear to show is that long-term pairs get into a groove with respect to territorial defense, targeting their defense towards times when it is most crucial. As with all good research findings, his raise a number of new questions. One obvious one is “Why should failed pairs be so inefficient about their territorial defense?”.    Another is “Must loons learn to defend their territories efficiently instead of doing so instinctively?”. These are exciting questions for the future that we look forward to tackling. For now, we are celebrating that Jeremy has just had his findings accepted for publication in the Journal of Avian Biology, a flagship scientific journal for avian research.