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.

I have just finished a rough draft of a manuscript describing the population decline of loons in my study area. That effort forced me to count and calculate, estimate and project. I like math, so the work was not unpleasant. I thought that I would pause and share some of the numbers I produced. First, let me share a complex graph!

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This graph shows two sets of values over an 18-year period. The blue line shows the proportion of all adults in the population that are floaters — that is, adults that lack a territory. This group includes both adults too young to have settled and old adults that have been evicted from a territory. The grey bars show the number of chicks banded in the study area three to four years before, adjusted for the number of territories covered those years. In short, the bars show how good the breeding years were in the study area three to four years before. I plotted things this way because three- and four-year-old loons make up the bulk of the new floaters each year, so by comparing the grey bar to the blue line, you can see what impact the breeding success three to four years ago had on the floating population. We expect that lots of chicks produced three to four years before will produce a surge in floater numbers. So the blue line should track the grey bars.

Okay, now let’s see what we can learn from the graph. Notice, first, that the blue line descends overall. This means that the proportion of the adult population made up of floaters declined during the past 18 years. Notice, next, that the grey bars are roughly the same height throughout the graph, which means that chick production was relatively stable over this interval. Already you should be thinking that something odd is going on. The blue line is NOT tracking the grey bars as closely as we expected. The bars and line DO track each other pretty closely at many points, however. For example, the stable chick production from 2002 to 2006 is paralleled by the stable floater population. 2008 went as we expected: good chick production 3-4 years before meant a positive bounce in the floater population. 2013 saw a loss of floaters, as we expected from low chick numbers 3-4 years before.

Now, focus on the last four years. Floater number had fallen to less than 40% of the adult population by 2015. Huge chick production from 2012 and 2013 should have “rescued” floater numbers in 2016 (caused them to spike upwards), but we only see a small bump up in floater numbers that year. And 2017 is worse as, despite big crops of 3- and 4-year-olds, there is a sharp downward turn in floater numbers! Likewise,  2019 should have seen an uptick, but floater numbers actually declined to an all-time low.

I know it is messy to look at this plot. If you find my fine-scaled analysis too picky, forget about the trees I have been discussing and look at the forest. Chick production during the past 18 years has been okay, yet consistently we see fewer floaters than we expect. This is the main puzzling finding of the paper I have written.

It is the mysterious loss of floaters, in fact, that seems to imperil the population of Oneida County loons. We estimate that there are about half as many floaters now as in the late 1990s and that the entire adult population has fallen by 22%. We do not know what is happening to the missing floaters — whether they are dying in their first fall, on migration, or perhaps during winter. But those floaters, which are  future breeders, will have to stage a comeback to get the population back on track.

 

 

Having read that northern Wisconsin loons are reproducing poorly and returning to the breeding grounds in very low numbers, many of you are probably wondering, “How widespread is the problem?”. Alas, most efforts to mark and monitor loon populations in other parts of the Upper Midwest have been fragmentary, short-term, and limited in scope. Lacking longitudinal data from other studies of marked individuals — the only kind of data that will permit a reliable assessment —  we cannot say whether other populations in the Upper Midwest have experienced the same downturn as our study population.

Two points are worth making here. First, the loons that we study in Oneida County do not exist in an isolated pocket. Rather, they are part of a continuous swath of loons that stretches from central Wisconsin to the Great Lakes, and northwards across most of Canada. Moreover, loons exhibit the sex-specific natal dispersal pattern characteristic of birds generally: males settle to breed close to where they were hatched and reared; females disperse much greater distances. So the female breeder on your lake is likely to be tens or even hundreds of miles from where she grew up, like the current female from Two Sisters Lake, who was reared on Crab Lake in Vilas County, or the female on Manson, who grew up on Rock Lake, also in Vilas County — or the female that dispersed over 200 miles east and wound up in Antrim County, Michigan. Hence, the loons in northern Wisconsin are part of a vast interdependent network that stretches to adjacent counties, states, and provinces. Females raised in Oneida County breed in Price County, Wisconsin, Michigan, and even Minnesota, while females from those distant places provide breeding females back to Oneida County. The whole system relies upon a dynamic exchange of females across great distances. In short, the downturn in chick production in northern Wisconsin does not spell trouble merely for local loons, it means fewer females are available to breed in outlying counties and adjacent states.

The second point to make is that the reproductive downturn we are seeing is not a short-term pattern that seems likely to reverse course. The inexorable nature of the decline — the fact that the numbers have been slipping downwards steadily for the past two decades — implies that some relentless, slowly-worsening environmental factor has been at work that reduces the abundance of small fishes in northern lakes and will continue to do so in the coming decades.

I am sorry for all of my gloomy forecasts of late. I know: I have only made it worse here by stating that I think loons might be in trouble throughout the entire Upper Midwest. In truth, I am deeply worried. But I am also thinking of strategies that we might use to learn what is hurting the loons and even possibly turn things around. First, of course, we must understand the problem. If it is food, that is not entirely bad news, because humans have been altering fish populations in myriad ways for hundreds of years. By targeted manipulations of small fish populations in certain lakes that we observe closely, we might be able to pinpoint the cause of loons’ reproductive decline, design a strategy for reversing it, and put loons on the comeback trail.

 

 

 

By now, most of you are aware that the loon population in northern Wisconsin is falling. Since my last report on this topic, we have made two separate formal calculations of λ (“lambda”), which estimates the number of adults in the population in year 2 divided by the number in year 1. Lambda is convenient and intuitive; if λ equals one, there are as many loons in the population this year as there were last year, and we are okay. λ greater than one tells us that the population is growing; λ less than one tells us that it is in decline. Our two separate calculations generated λ values of 0.96 and 0.94, which indicate that the loon population in Oneida County is currently falling at a rate of 4% to 6% per year. The picture is somewhat worse, it seems, than we had thought a few months ago.

This rate of decline — if it is correct, and if it persists — is grave news for humans who love loons. If these numbers are accurate, we will notice the effects of the decline within the next several years. Territory vacancies will go unfilled. Pair members that lose their mates will struggle to re-pair with new ones. Still fewer surviving young will fledge than do now. And our loons will have entered the dizzying downward vortex of a dwindling population.

In the short term, though, one cohort of the loon population benefits from falling floater numbers. The sharp downturn in floater abundance has territorial pairs breathing a sigh of relief. For breeding males and females, you see, fewer intruders — fewer scenes like that depicted in Linda Grenzer’s photo above — means fewer young upstarts seeking to evict them from their territories and a higher rate of territory tenure. How much better off are breeders? As the plot below shows, they are a good deal better off.

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The threat of being evicted from a territory in a given year is now only 1/4 to 1/5 what it was only two decades ago. Small and/or old loons that were lucky to hold a good territory for a year or two in 1998 can kick back and relax nowadays, because the eviction rate is trivial. The decreasing floater population is making the prospect of lifelong breeding on a single territory look like a reasonable expectation for both sexes. People who have become familiar with the breeding pair on their lake might feel better off in the short term. They can be much more confident now that the birds they greet each April are the same two from the previous year.

Though I feel that I know several dozen of my study animals reasonably well and look forward to seeing them each spring, I cannot celebrate the fact that I now stand an even better chance than before of doing so. To me, the dynamism of the system — the likelihood that a breeding female or male might have to accept eviction, lick its wounds, and find a new territory with a new mate nearby — was part of its beauty. Knowing what I do now, each reunion with a familiar breeder for me will be a reminder of the new normal: unnaturally long breeding tenure made possible by the drastic decrease in territorial challengers.

It is only a glimmer — the kind of glimmer one often gets when eyeballing new data. But the implications of this small discovery are enticing.

You see, I have been looking at our data on tameness, Since 2014, our team (mainly Kristin, Seth, Mina, and Nelson) has measured tameness of loons by creeping up to birds resting on the surface. We do this by first measuring our distance to the loon with a rangefinder and then paddling slowly in its direction, taking distance readings every few strokes. The final distance reading — just before the loon dives to avoid us — is our measure of tameness. Determined in this way, tameness varies from well above 50 meters to less than 2 meters. (In fact, some of our marked birds, like the male in Linda Grenzer’s photo above, find our approach so unremarkable that they simply veer slowly out of our path, instead of diving.)

We can examine the origins of tameness in far greater depth than most other studies, because we have tameness readings on many sets of close relatives in the study area. In fact, owing to the duration of our study, the limited natal dispersal of many individuals (especially males), and our efforts to find adults that we banded as chicks, we now have tameness measured for 60 sets of relatives. These include Linda’s male (“Clune”) and his son, who breeds on tiny Virgin Lake; the notoriously skittish male on Oneida-East and his full brother on Hughitt; and the Bear female and her full brothers on Cunard and Gilmore (all three banded 13-15 years ago on North Nokomis Lake).

As the figure below shows, we have noted a strongly and statistically significant relationship in tameness between parents and offspring. This pattern implies that either: 1) offspring inherit their tameness from parents, or 2) parents teach their offspring to be tame or skittish during the chick-rearing phase (or both). Either way, similarity in tameness between adults and their young means that despite being measured on different lakes, many years apart, and at very different ages, tameness is stable within individuals and is largely fixed early in life. A loon’s degree of tameness is, in effect, part of its personality.

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Parent/offspring similarity in tameness is more than a hollow novelty. Since tame parents produce tame young (either via genetics or rearing environment), those young should respond to the habitat in much the same way as their parents. I am in the process of writing a proposal to the National Science Foundation to study, among other topics, the possible impact of loon tameness on habitat selection. Specifically, I wish to test the hypothesis that tame loons might be suited to lakes with lots of human recreational activity (generally large lakes) and skittish loons to lakes with limited human activity (generally small ones). If this logical hypothesis holds up, then pity skittish individuals. Since human activity is increasing, and even many small lakes now see frequent human usage, skittish loons appear to have a small — and shrinking — set of lakes on which they can breed. Moreover, the reduced chick production of small lakes might also doom skittish loons to poor breeding success, so that fewer skittish individuals are produced each year.

The long-term consequences of parents passing skittishness to their young and fewer offspring produced by skittish loons are easy to guess. Tame loons will produce a large proportion of all offspring in the northern Wisconsin population, and tameness should increase in frequency in coming decades to the point where skittish loons are hard to find at all. This vast behavioral shift might go unnoticed by most observers, since there will still be loons on the lakes. But to an ecologist, it is exciting to think that we might be on the brink of learning the precise mechanism by which a population of an important animal can become tame.

 

 

In the dream, I am swimming in a tiny lake – a lake so small that two residents on opposite ends of it could converse without raised voices. The lake is completely encircled by cottages. Docks overhang almost every inch of shoreline, looming menacingly over the water and rendering the lake smaller still. The lake, in fact, looks more like a pond hastily dredged by developers for a suburban apartment complex than a pristine aquatic habitat where loons might live. But in the dream a pair of loons swims about the lake with me, investigating future nest sites after having lost their first nest of the year to a predator.

I awoke yesterday with this dystopian scene vividly in mind. The dream reflects, I suppose, my growing unease over the future of loons along the southern fringe of the species’ breeding range. My concern is fueled by an ongoing analysis of the decline in chick survival since 1993.

That analysis has progressed since I first mentioned it. The investigation started as just a hunch — an uneasy feeling that singleton broods were becoming more common. Now, having looked at the data formally in a controlled analysis, I have brought the decrease in brood size more sharply into focus and verified that it is real. There has been a systematic, highly non-random decline in brood size over the past quarter century in Oneida County.

My worst fear took shape in the dream. I fear that growing recreational pressure, shoreline development, and perhaps environmental degradation have conspired to rob breeding pairs of a chick here, a chick there — to the point where the population might be affected. My recent analysis provided a hint about the cause: the decline is far greater on large lakes than small ones. Large lakes, of course, are those most affected by increased human recreation.

It is early still. I have much investigation yet to do, especially testing specific measures of human activity (like fishing or boating licenses issued in Oneida County) to see if they are tightly correlated with chick losses. But for a worrywart – and a vivid dreamer – these are unsettling times.

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.

 

 

 

Since snow and ice lingered far too long this spring, loons were late to nest in northern Wisconsin. The lateness of the season has also reduced opportunities to renest after early nest failures. There was simply limited time for pairs to weather four weeks of incubation and still rear the chicks to a point where they could learn to fend for themselves and make their way to Florida. Add to the narrow window this year the mishaps that cost us young chicks on several territories….and I was beginning to sweat.

But my fears of another off-year for nesting success in the Upper Midwest loon population have not been realized. A relatively short period of black fly abundance has helped immensely. As our recent paper showed, abandonments from black fly harassment are a good predictor of nesting success; that pattern has continued in 2018. So it seems likely that this year will break our four-year breeding slump.

Here are the numbers. As of July 4th, we had an estimated 48 breeding pairs in our study area with a chick or chicks. Eighteen (give or take a few) were still on nests, of which over half will produce chicks also. That leaves us with roughly 60 loon pairs with chicks. A handful of the 60 pairs will lose their chicks before 8 weeks; in addition, though, we will make roving visits to non-study lakes within and just outside the study area and find about 6-8 more pairs with chicks. When the dust has settled, we should end up with a number of pairs with chicks that is very close to the 65 successful breeding pairs we were able to band in 2013. That fact is worthy of note, because 2013 was both a year in which our procedures and lake coverage were similar to this year, and the last solid year of breeding. So we can all breathe a great sigh of relief — and enjoy Linda’s cool photo of the freshly-hatched chick on Muskellunge Lake and the female, with moist eggshell fragments still adhering to her breast.

Breeding prospects for loons in northern Wisconsin seemed dim only three weeks ago. Not only had a frigid April delayed the start of nesting, but Simulium annulus was doing its best to keep loons from warming the eggs that had taken so long to appear. A statistical correlation between cold spring temperatures and black fly harassment had me fearing that the long-awaited nests would be abandoned in short order – delaying the season still further. My hopes for a bounce-back year of breeding, after 2017’s disappointment, seemed distant.

As I keep learning in life, unfathomably horrid situations often improve. So it was this spring. To be sure, loons were forced to abandon a few early nests – those at Langley, Fox, and Wind Pudding-East, for example – owing to fly harassment. But loon pairs that had been reluctant incubators in mid-May suddenly bent to the task late in the month. Even after accounting for the inevitable wolfing down of eggs in exposed nests – such as those at Two Sisters-Far East, Long, and Little Bearskin — by raccoons and their ilk, the vast majority of our breeders are sitting on eggs (like the male on Linda’s lake; see photo). At last count, 79 of 123 pairs we cover are on nests that have survived the crucial first ten days. Two weeks or more of incubation remain for most of these territories. But barring some unforeseen disaster, 2018 might be one of the most productive years for northern Wisconsin loons in the last quarter century. Who would have guessed that a breeding season that started so inauspiciously would gain such momentum?