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?

As many of you know, I am a worry-wart. Normally I get so stressed-out about my kids, my teaching, my research, my health — and many other matters that are going well — that I hardly have time to obsess about loons in the study area. But Linda Grenzer’s bleak photo of conditions on her lake today gave me a jolt. Could the late ice-out that we are facing in 2018 delay the season so much that it damages the breeding prospects of our loon population?

One might think that the later the ice comes off of the lakes, the later the loons nest, and the less time parents have to fatten up their chicks and prepare them for their first southward migration. Thus, a late ice-out might well lead to reduced breeding success for the population. Although there are many “if”s in this string of logic (and a preliminary analysis did not bear out the pattern), I felt concern  gnaw at me.

So I did what scientists often do to stave off despair: I looked at the data. First, I looked to see if loons nest later when the ice goes out later, which almost has to

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be true. It is true, but there is a lot of noise in the data. That is, loons are constrained to nest somewhat later in years when the ice goes out later, but the picture is not simple. The reason for the noise becomes clear when you look at the lag time between when loons settle on their territories and when they hatch their

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young. There is a very strong pattern here. When the ice goes out early (left side of graph), loons dawdle and wait weeks before nesting. But when the ice goes out late, as it will this year, pairs get down to business quickly, nesting within a week or so of territory return. So loon pairs are somehow able to catch up in years of late ice-out so that their breeding schedule does not differ greatly from other years. (Notice also that the orange line in the top graph is flatter than the blue line.)

What accounts for this pleasing pattern? We can make a pretty good guess based on findings in other migrant birds. Spring migration is an energetically costly process. In an early year, the ice is gone so quickly that loons settle on their lakes as soon as they return from the wintering grounds. In such cases, their fat levels are very low from migration when they first occupy their territories, and it takes a good deal of foraging before they return to good condition. In a late year, loons cannot settle on their territories right away but must wait on nearby rivers that have open water. There, they are able to forage and restore their bodies to good condition. As a result, loons hit their territories in prime body condition and fully recovered from the migratory flight in years of late ice-out. Thus, they can get down to breeding quickly.

Although I was heartened by the data I saw above, I had a look at the numbers that most directly addressed my concern about late ice-out and population breeding success. There is a no statistical tendency for the population to produce more loon chicks in years of early ice-out, despite the many years of data we have to look for such a pattern. Indeed, some of our best years for loon breeding (2013, for example) have occurred when the ice goes out late. So those many of you shivering in northern Wisconsin and other frigid regions can relax about one thing; the loons are no worse off in years when spring comes late than when it arrives early.

In a sense, our ability to identify loons as individuals hangs by a thread. As most of you know, we rely upon a unique combination of three colored leg bands — together with the mandatory numbered USGS metal band — to ID our study animals. The Upper Kaubashine female, for example, is “silver over yellow on right leg, red over green on left leg”, while the Lee Lake male is “blue with white stripe over taupe with white stripe on right, red with white stripe over silver on left”. (He is nicknamed “Stripe Hell” by my staff.)

The system seems simple enough on its face. Together with the DNR, however, we have banded over four thousand adults and chicks in northern Wisconsin since 1991. Thus, we have used a lot of color combinations over that span. Inevitably, certain individuals differ only slightly from other individuals in their band combination. While we make every effort to use contrasting band combos on mated pairs, loons move around between lakes because of natal dispersal (movement from natal lake to breeding lake) and eviction. Sometimes birds with similar band combos end up close together. For instance, the male on the southeastern end of Squash Lake, which we caught last night, is “yellow over taupe stripe, green over silver”, while the female at the northwest end of the same lake is “red over taupe stripe, green over silver”. A single band is crucial to distinguishing one bird from the other on Squash.

I describe our identification system as fragile, because the loss of only one of its four bands by a loon can throw its identity into question. In several cases, a loon with one or more missing bands could only be ID’d when it was captured and we read the number on its USGS metal band. In most years, there is at least one such “mystery loon” in our study area.

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Our mystery loon of late has been the female on Bear Lake (pictured above in Linda’s photo). She has lost one band and is now “orange over mint burgundy, silver only”. A check of our banding records finds four birds that could match that combo, if they lost a single band. All are “ABJs”: adults banded as juveniles. In other words, all were marked as chicks: one in 2004, one in 2005, and two in 2007. I was excited to see that Bear Lake had a chick this year, because this gave us a reasonable chance of being able to capture Mystery Female and learning her age and natal origin from her metal band. But she is a skittish bird, and we failed to catch her.

So we left it to Linda. Linda is a great photographer and a very patient naturalist. Many times she has taken photos so crisp that one can read the numbers stamped into the metal band on birds legs. Below is an example of a photo by Linda in which one can make out several numbers on the metal band on the right leg, above the “auric with red stripe” band. I thought that Linda might pull off the same magic with

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the Mystery Female, which would permit us to discover her age and natal lake. Thus far, she has been able to make out three separate digits on the bird’s metal band. That information has allowed us to eliminate two of four possibilities; we now know that the Mystery Female was hatched on either North Nokomis Lake in 2005 or on Buck Lake in the same year. The tendency of young adults to settle on breeding lakes similar in size to their natal lakes makes us favor North Nokomis as the more likely natal lake. If we are lucky, Linda might get a chance to nail the numbers well enough for a certain ID.

Now you might wonder why we are so obsessed with the identity of a single loon. After all, we have identified scores of other lake settlers who held onto all four of their bands. We have come to feel that each data point is precious, because each one allows us to refine our population models and survival estimates. Females are particularly valuable to us, because most of them disperse so far from their natal lake that we cannot relocate them as breeders. (Males, in contrast, often settle within a few kilometers of their natal lake, so we have far more data on male settlement.) So please send positive vibes Linda’s way, as she hunts the skittish Mystery Female of Bear Lake.