Most scientific research comprises snapshots of a biological system. That is, we usually study the behavior or ecology of an animal for a year or two in a forest, on a coral reef, or in a desert. On the basis of such a short term study, we pontificate about what constitutes a good territory and what constitutes a bad territory for the animal we are studying. Then, feeling that we have described the system accurately, we fold our tents and move on to the next study and habitat.

But time changes things. My team and I got a demonstration of the impact that time can have yesterday when we visited two lakes located towards the northern part of our study area. Life has always been hard for loons on Dorothy and Hodstradt lakes. They are both rather clear lakes and full of fish. But they have been disasters reproductively, because they lack the islands, marsh, and bog that loons seek out to keep their eggs safe from raccoons.

The gradual but now-dramatic rising of lake levels in the Northwoods has produced a spectacular reversal of fortune for loons on Dorothy and Hodstradt. What had been an unremarkable spit of land on Dorothy has become an island several meters offshore, reachable only by water (see photo below). What once was a long curving peninsula on Hodstradt has been transformed into an island, accessible only after a lengthy swim. In short, two lakes for which chick production was a freak occurrence have now become prime real estate, because they offer offshore nest sites inaccessible to all but the most ambitious raccoon.

Of course, the rising waters have not been kind to all lakes. Heiress Lake had a handy island that saw regular chick hatches in the late nineties and early 2000s. But no more. That raccoon-proof site is now four feet underwater, and Heiress no longer supports a breeding pair.

The take-home message is clear: territory quality is not fixed and unchanging. Instead, changing climatic patterns transform the landscape in surprising ways. A goldfinch’s lifespan is short enough that habitat transformations probably matter little. But loons live long enough to see poor nesting habitat become good nesting habitat and vice-versa; this species should be able to detect and respond adaptively to fluctuations in territory quality.

In fact, loons do exhibit some ability to respond to changing landscapes. We see this ability in the willingness of breeding pairs to explore vacant lakes near their original one and sometimes nest at sites different from those they have used to hatch chicks. And, of course, young nonbreeders use the presence of chicks on a territory as a measure of current reproductive quality so that they can target lakes for eviction attempts that will reward them with many offspring. On the other hand, many adults settle on a productive territory during the prime of their lives only to see its quality decline along with their own body condition. Lacking the fitness to defeat an opponent in a battle for a new territory, such birds are stuck breeding on a failing territory. These old codgers could tell ecologists a few things about territory quality and the passage of time. 

I sometimes dwell on the negative. In fact, those who know me well no doubt would regard that as an understatement. Strangely, I myself forget that I possess this trait. As a result, I often careen downwards over periods of days or weeks, seeing one after another of the unpleasant aspects of a certain committee I sit on, a basketball team I watch, or a politician whom I hear speak. Eventually though, my negative jag launches me into something unambiguously positive that contradicts all earlier evidence and forces me to pause and reconsider.

So it has been in recent weeks, as I have worked on a team of loon biologists revising the common loon account for Birds of North America. While the long-term, downward trajectory of my study population had me in a funk, talking to and working with these folks (especially David Evers) has given me a broader, more balanced view of how loons are doing along the southern edge of the species range. This has turned me around.

As Dave pointed out to me, the picture of loon breeding in other parts of the U.S. is quite a bit rosier than in northern Wisconsin. While not all of the data are reliable, there seems no question that loons are thriving in Maine, New Hampshire, Vermont, and Massachusetts, having experienced double-digit increases in adult populations in the past decade. These findings contrast sharply with Upper Midwest loon populations, which have shown little or no change. In Minnesota and Michigan, according to our latest measures, populations are merely stable. Wisconsin loon populations, while they increased greatly during the 1980s, 1990s, and even early 2000s, have been measured as stable or declining in recent years.

So the overall picture of loon populations along the southern edge of the breeding range is mixed. But things look so good for the species in New England that, even after considering the slightly negative recent trend from the Upper Midwest, we must conclude that overall the U.S. loon population is doing fairly well.

The uneven geography of loon population patterns raises an important issue. Could the burgeoning New England loon population supply young adults that settle in the Upper Midwest, breed there, and thus rescue our struggling population? No, this cannot happen, because young loons do not disperse far from their natal lakes to breed. A few of the chicks that we have marked in Wisconsin have made it to Michigan, and one or two of these thousands probably has settled in Minnesota (though we have no reports to date), but none has gone farther afield than that. The stability of the Upper Midwest loon population relies solely upon the successful reproduction of Upper Midwest adults. In other words, we are on our own.

Still, the mere fact that loons are reproducing well and expanding their population somewhere is heartening. It suggests that factors causing the decline in the loon population in Wisconsin might be local ones, not sweeping ones, like climate change. Or it might mean that factors that could lead to loon population declines — whatever those factors are — can be reversed by intense local conservation efforts, such as occur in New England states.

At any rate, I am looking at the world a bit more cheerily now, after learning about thriving loon populations in New England. With my tunnel vision always focused more on things loon than things human, there is reason for hope.

The Audubon report put me on notice. Loons are not immune from climate change. While I have wondered at times whether their aquatic habitat might somehow buffer them from the warming of the Earth and increased moisture in the atmosphere, this was a false musing. Recent changes in temperature and precipitation have myriad and complex effects on lakes and their inhabitants. Loons will have to confront the changing conditions just like all other organisms must.

I wondered whether my long-term data on loons might show climate-induced changes. I am not a climate scientist — nor even a hard-core ecologist who might routinely measure fish populations, water temperatures, or lake chemistry. But we do weigh all loons that we capture and band. Perhaps masses of adult loons or chicks have fluctuated in response to the changing climate.

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My findings are quite striking. Chicks have decreased in mass consistently since my team began capturing and marking loons. This finding alone is worthy of concern, but it is not the only one. Breeding males (see below) too show a decline in mass during our study. Breeding females, on the other hand, show no steady loss in mass.

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What are we to make of these patterns? Are populations of small fish down in the past few decades such that chicks and their male parents struggle to put on or maintain body mass? Or are lakes changing in ways (e.g. clarity) that might make fish more difficult to catch? Whatever the cause of these decreases in mass, why are female loons not affected similarly? These questions must remain unanswered for the time being. In fact, these results are so new that I must run some more double-checks before I fully trust them. Even if they are real effects, as it appears, it is much too early to attribute them to global warming. My worrying self, though, fears that these significant declines in body condition might be the leading edge of a changing climate’s impacts on Wisconsin loons.

The Loon Project is my life’s work. While I greatly enjoy teaching Chapman students, serving on committees with my colleagues, and living in southern California, a part of me resides permanently in the Northwoods with the loons.

I inherited my love of loons. Mom introduced me to them in the 1970s when we made trips to Temagami, a deep, clear, sinuous, 30-mile-long lake in central Ontario. “Listen… you hear the loons?” she would ask my brothers and me as we lay beneath thick woolen blankets. As a resident of far-off Houston, I recall feeling awe, and some fear, to hear the mournful wails and maniacal tremolos echo across the huge lake. I wondered what messages loons could be sending each other in the middle of the night.

So I guess I was predisposed to study loons when I re-encountered them in Michigan’s Upper Peninsula in 1992. By the time I had finished listening to Dave Evers (then director of the Whitefish Point Bird Observatory) describe battles for territorial ownership that he and his staff had witnessed during their capture and marking efforts, I was hooked. At first, I implored him to conduct further research. “Your observations suggest a cool territorial system in loons, Dave. There are important questions about behavior and ecology to address here.” But Dave’s interest was not territorial behavior. If anyone was going to follow up those exciting early findings, I, a trained behavioral ecologist, would have to do it.

I began my loon study in 1993 and ran the project on a shoestring back in the mid 1990s. Then a postdoc at Indiana University, I really had no business setting aside my work on parentage analysis by DNA fingerprinting – expertise much sought-after by universities at the time – for a logistically-challenging project that required an enormous investment of time and energy. There was no low hanging fruit here. Several years were required simply to collect enough data to publish my first paper.

It took a decade — until 2003 — to pull together a sufficient cluster of banded loons and early findings to convince reviewers at the National Science Foundation that I was doing productive, cutting-edge research. I was awarded additional funding in 2007 and 2012. But funding rates for ecological proposals are now in the 7 to 9 percent range — roughly a third of where they were 30 years ago.

I love my work and have enjoyed learning about loon behavior, ecology, and population dynamics over the past 27 years. The project is more important now than ever before for loon conservation. With the future of loons in Wisconsin somewhat in doubt, our long-term measurement of breeding success and territory occupancy of marked birds in a large, fixed set of lakes provides us with a vital “early warning system” to detect population decline.

I am excited to invite you to support my efforts to learn about loon behavior and ecology while creating educational opportunities for undergraduates. Here is a link that will take you to our brand new “Donate” page. Thank you in advance for any amount you are able to give — and for your commitment to the loons of the Northwoods!



Recently, I made the kind of finding that gives scientists fits. It came about in the same manner that findings often do initially: a hunch.

Since I spend much of my life either working closely with loons or poring over data that describes their breeding success, I am in a good position to notice subtle changes that occur over time. Occasionally when out on a lake, I observe a breeding event and think, “Wow…..that did not happen in the old days!” Then I retreat to my computer, look at data from years past, and see if I am correct. I have to confess: in many cases, I am wrong.


This past August, I noticed what I thought might be a growing pattern in breeding ecology. Mated pairs, it seemed to me, were less often rearing two chicks to fledging. That is, they were either hatching one chick and rearing the singleton only or hatching two chicks and losing one. At least that was my impression. In this case, field data confirmed my suspicion, as the above graph shows. The proportion of singleton broods has risen during the study. In three of the past five years, in fact, two-chick broods were quite uncommon, making up only 1/5 of all broods. Most of the pattern, moreover, appears to result from failure of one of two eggs to hatch, rather than loss of the second chick after hatching.

Faced with a puzzling and unexpected finding, I looked immediately at the usual suspects. Black flies, which have also been worse in recent years, are an obvious possibility. Flies harass incubating loons, reduce incubation times, and might reduce hatching success. In fact, I was convinced when I wrote our recent paper that black flies were the culprits. But then 2018 happened. This season featured a warm spring, a rapid die-off of flies, and very few fly-induced abandonments. So we could not blame flies for the low hatching rate of eggs in 2018.

What about the changing climate? As I have emphasized in a recent post, warm weather is projected to drive loons northwards; could it also be the root cause of the lower hatching rate? I looked to see if warmer May temperatures are correlated with reduced hatching, but they are not. (In fact, warmer temperatures are associated with a slightly higher hatching rate.) Likewise, precipitation might, in theory, reduce hatching rate. Again, years of higher May rainfall were not years of lower hatching success. I breathed a sigh of relief to learn that the lower rate of hatching does not (preliminarily) appear to represent the harmful leading edge of climate’s impact on loons.

Two possibilities remain. First of all, there is a small chance that the pattern is a statistical anomaly — that hatching rate is not actually falling, but that the result occurred by sheer chance. Scientists must always be circumspect about their results, and the statistical test says that there is a 0.6% chance that the finding does not represent a true pattern. (That is roughly the likelihood that you toss a fair coin 9 times in a row and get “heads” every time.) Second and more likely, some unknown factor is at work here. Might there be an environmental contaminant, picked up by loons, that increases developmental abnormalities in embryos or perhaps causes adults to cease incubation of the second egg prematurely? Might disturbance of incubation by humans be the cause of lower hatching success? These possibilities — and numerous others — generate testable predictions, and I will test them. In the meantime, let’s all keep our fingers crossed that the distinct decline in loon hatching success over the past 20 years is, after all, just a blip.




Humans are not good at thinking about the distant future. We are not alone in our short-sightedness. Living things, in general, are obsessed with the here and now and oblivious to what lies far down the road. There is a very good evolutionary reason for focusing on the present. Animals that succeed at surviving and protecting their progeny leave more young than other animals (in this case, hypothetical ones) preoccupied with what conditions might be like for their grandchildren and great-grandchildren. Animals that attend to their own survival and that of their offspring simply leave more offspring. Thus, natural selection can be said to favor animals that focus on the present — and animals within natural populations are chiefly descendants of parents and grandparents that cared for their own survival and that of their offspring. The short-term view makes sense evolutionarily.

Our very logical tendency to heed the here and now at the expense of the future has a limitation. Focus on the present adapts animals well to a stable environment, but leaves them poorly adapted to an environment that changes rapidly. Over evolutionary time, environmental change has generally occurred slowly enough to cause little problem for animals that live only for the present.

But humans have hastened environmental change. Anthropogenic changes have taken many forms, including introduction of invasive species, environmental degradation, and wholesale alteration of landscapes and vegetation. Perhaps surprisingly, many non-human animals have been able to keep pace with human impacts. In fact, some — crows, gulls and raccoons come to mind — have benefitted enormously from human activity. Others, of course, have become extinct, endangered or have seen their geographic ranges contract because of humans. We could quantify human impacts of each and every non-human species, if we cared to, and place each on a chart from least- to most-impacted.

Where on the chart would the common loon fall? Considering that loons are often viewed as the “voice of the wilderness”, one might suppose that they would suffer greatly from human encroachment. In fact, loons are hanging in there better than many other vertebrate animals. Knocked back in the middle of the 20th century, the common loon population has rebounded. Breeding populations are now generally stable or even increasing across most of the northern tier of United States. So loon populations appear to be hanging in there despite extensive shoreline development, entanglements with hooks and fishing line, and increases in methylmercury levels, among many other challenges.

A new anthropogenic threat now looms that is more extensive and unrelenting than others that loons have faced. Climate change has already caused many geographic ranges of North American animals to recede northwards. A recent study showed that bird species differed greatly in their northward shifts, but that, on average, breeding ranges are marching northwards by over 2 km per year. We have a bit of an apples and oranges problem here; the bird species included in the study varied greatly in their diets and habitats. Some, no doubt, are highly dependent upon temperatures (and related factors like vegetation) for their survival; others are not. So it is difficult to project precisely how the geographic range of the common loon might be affected. But do this: take a look at Audubon’s animated depiction showing the contraction of the loon’s breeding range.

Two patterns are immediately clear from the animation. First, the northern Wisconsin loon population (and abutting populations in Minnesota and Michigan’s Upper Peninsula) exist on an isolated “finger” that projects southwards from the heart of the range, which lies in Canada. Second, the model paints a very bleak picture of the future loon population in northern Wisconsin. According to the model, loons are projected to be much less abundant in northern Wisconsin by 2050 and gone altogether by 2080.

Now, a word of caution. Audubon scientists have attempted to distill the climate down to two main factors: temperature and precipitation. On the basis of these two climatic factors, the current distribution of the species relative to these factors, and the projected future climate based on the report of the Intergovernmental Panel on Climate Change (IPCC), they have produced the  animated graph that loon enthusiasts like us find so disturbing. Their projection is likely to provide a crude estimate of the impact of climate change on loons, not a precise one. That is, loons are likely to cope with climate change better than most other birds — as they have other environmental threats. Then again, loons might be especially sensitive to climate change and retreat northward more rapidly than the study predicts.

Like many other humans, I am obsessed with the day to day. I have studied loons as if they would be around forever. I have battled to obtain grants to keep my study afloat, to publish my papers in high-impact journals, to hire diligent field technicians who would collect reliable data. Now, forced by changing environmental conditions to glance towards the future, I can scarcely believe that the animals that I have learned so much about and grown so fond of might be well on their way to vanishing from Wisconsin in my lifetime.