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. My study area in northern Wisconsin is typical; loons have re-colonized many lakes in the past few decades from which they had retreated. So loon populations are thriving 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.

We always celebrate when someone identifies a new banded adult. “You got an exclusive!”, I say to one of my students, if they nail all bands on a loon that we banded as a juvenile in the study area and have not seen since. In fact, Melanie reported an exclusive ABJ (for Adult Banded as Juvenile) just yesterday; this one happened to be a four-year-old male hatched on Samway Lake that she ID’d on Elna. (Linda’s photo shows an exclusive that she nailed bands on, this one from Soo Lake.)

Sightings of young ABJs are valuable. These loons are all “floaters” — nonbreeding individuals that live on small lakes or parts of large lakes that are not used by breeding pairs — so they live a marginal existence. Still, they provide us with data on juvenile rates of survival and return to the study area, which contribute to mathematical models that tell us whether our population is stable, increasing, or decreasing. Young ABJs are also the future, because these green, reticent individuals — they are notably subordinate when interacting with territorial residents, have low fighting ability, and are well below optimum adult body weight — will ultimately replace our established and well-loved territorial breeders.

I spend most of my research time asking behavioral questions about our long-term territorial residents, which is regrettable, because it leaves young ABJs out. In fact, a vexing question concerning young ABJs has been lurking in the back of my brain for some years now: where do they all go? From the countless small celebrations the students and I have had over the years at new ABJ sightings, an expectation has formed that we would see a vast wave of new territory settlements by this youthful cohort. But it has not happened. Each year only a handful of young ABJs claim new territories by evicting a living territorial resident, replacing a resident that has died, or carving out a new territory where there was not one previously.

This morning I got fed up with waiting around for all of the young ABJs to settle — and looked at the numbers. They are pretty shocking. We have been able to celebrate sightings of 348 young ABJ floaters over the years. That is a lot of loons. Of these, though, only 124 settled on breeding territories and paired with a mate for at least 60 days. And an even smaller number — 94 — nested and hatched chicks. Since most of these individuals were last seen years ago, most died long ago. So only slightly over one-fourth of all young ABJs that returned the breeding grounds ever produced young. Even this rather low fraction is too high, because it presumes that we actually ID all young ABJs that come back to the study area. Clearly a typical young ABJ deals with many challenges — lengthy migrations between breeding and wintering grounds, bouncing around in the study area, probing here and there for territory openings, absorbing attacks and chases at the hands of territory owners — only to fall short in that last, most crucial test: territory settlement.

Why? Why would the rate of failure to settle be 75%, when vacant lakes with a successful record of chick production abound in the study area? If I were a loon (I know….but don’t say it!), I would look around for a prime breeding territory, pick a few fights to try and get one, and then settle for a less-than-perfect but adequate territory, if it came to that. Because failure to settle leads to evolutionary oblivion. That is, we expect that natural selection has acted on behavior in such a way as to maximize breeding success, and breeding success would appear to be maximized not by failing to settle but by settling wherever you can and cranking out as many chicks as possible there.

Of course, it is hubris to think that humans know how loons should behave. Loons have been molded by natural selection and other evolutionary processes for countless generations in a way that virtually guarantees that their behavior leads to high evolutionary fitness. However, as my students in Animal Behavior class know well, there are a few caveats to the expectation of sensible, adaptive behavior by animals. The main one is that rapid environmental change can sometimes outpace the capacity of animals to adapt, causing animals to behave in a way that does not maximize their reproductive success. In other words, if the environment that an animal faces — its predators, competitors, physical environment, etc. — changes so rapidly that the species cannot evolve suitable behavioral adaptations, then we might see animals behaving “foolishly”. So we might surmise that ABJs fail to settle on vacant territories because the availability of vacant territories has only recently increased, and loon settlement behavior evolved during a period when vacant territories were scarce. In effect, then, ABJs would be practicing behavior not suited to the territorial situation that now exists.

While we cannot reject the hypothesis that rapid environmental change has made loons look stupid, it is a bit hard to stomach. The hypothesis posits that young floaters are poor settlers because they are not used to territories being readily available. But whether territories are scarce or abundant, young floaters should have evolved to be able to occupy any available one readily. That is, the capacity to snap up a vacant territory is so fundamental that it is a trait that should be possessed by all young loons, regardless of the territorial environment in which they evolved. There must be a better explanation for the failure of so many young ABJs to settle on territories.

The reason for lackadaisical territory settlement by floaters is probably habitat preference. Some of you may recall that young loons show a peculiar but very strong preference for natal-like habitat. Specifically, young floaters from small, acidic lakes strongly prefer to breed on small, acidic lakes, and those from large lakes of neutral pH try to establish themselves as breeders on large, neutral-pH lakes. Strong habitat preference creates a situation where a young floater reared on one kind of lake does not see vacant territories on another kind of lake as a viable breeding option. If young ABJs are being finicky about the territories they choose to settle on, we should expect to see some “perfectly good” territories go unsettled, as we do. More to the point, we should not be surprised that many floaters fail to settle.

Natal habitat preference might help us understand the seemingly inefficient territory settlement of young floaters, but, if so, it merely shines a spotlight on another vexing question: why do loons strongly prefer to breed on lakes that resemble their natal one? I have speculated about this before, but no satisfactory answer has yet emerged. As we collect more and more survival data, we might find that loons have evolved to take into consideration more than just the potential of a breeding lake to produce chicks. Indeed, settling on a territory like your natal one might mean that you were prepared since day one for that kind of environment and might be able to survive well there. If so, natal habitat preference might allow you to offset with longevity any loss you suffer from settling on a territory that is less-than-stellar for producing chicks. The slow but steady approach of rearing a chick here and a chick there but surviving to a ripe old age might be the one that maximizes lifetime breeding success.

I have an almost-annual tradition. Each year at this time, I watch helplessly as black flies harass incubating loons, drive them off of their nests, and force them to dive to gain momentary respite. In years of mild infestation, I breathe a sigh of relief to see that the nest abandonment rate is low. In severe years, I sit down at my computer and try to determine what factors might cause the little demons to hammer loons so hard. Today, I found this. Rate of nest abandonment is strongly correlated with April temperatures. Specifically, cool Aprils seem to cause more nest abandonments. The pattern is strong.

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As usual, I am late to the party. Black flies are of considerable interest because of their negative impacts on humans and domestic animals, so we know a good deal about their biting habits. An hour ago, I excitedly e-mailed one of the world’s experts on black flies to report that cool weather seems to lengthen the period when these pests bother loons. “I am onto something”, I thought. “I must get the word out.” He politely informed me that cool water temperatures slow the emergence of the flies, and cool air temperatures stretch out their lives. He then pointed me to thirteen scientific papers from the past half-century that reached the same conclusion!

The momentary humiliation I experienced was a small price to pay for the knowledge gained. I am now poring over this literature to learn what I can. I have found that most studies of black fly biting patterns are quick-hitters — snapshots from black flies caught in traps over a year or two. Since we possess over two decades-worth of data, our nest abandonment finding expands the information pool considerably. In addition, we have not merely measured how many flies are around or biting, but their apparent impact on the breeding productivity of a well-loved bird. So my excitement about our result is only slightly diminished.

Setting aside the scientific significance of our finding, what does it mean for the Wisconsin loon population? We cannot control outside temperatures, so there seems little hope that the finding will help us mitigate the impact of black flies on loon nests. But if I am correct that cool Aprils are most damaging to loon nesting — and this is a big “if”, as I am still exploring the result — then we might have cause for guarded optimism. A warming climate, while harmful globally in many respects, might provide a slight lift to nesting loons.

 

LMG2693 Loon Between the Ice

I always dread ice-out. While I am excited to know that I am scant weeks away from seeing the loons, ice-out now tends to occur during the high-stress period of the Chapman spring semester — and I am seldom ready for the event. As Linda’s photo from the Wisconsin River shows, loons are coming back, accumulating on the river, waiting for their breeding lake to open up enough to permit landing there. Meanwhile, my Animal Behavior students are sweating their behavioral experiments and write-ups.

Let’s focus on the positive of early ice-out for data collection. Rain and warming temperatures mean that ice-out is only days away. Soon we will begin to log the identities of returning veterans anxious to attempt another year of breeding. Since the lakes will be habitable two or more weeks before the historic mean date of ice-out, while many returning birds are still en route from the wintering grounds, we have an opportunity. In theory, adult loons that are in good physical condition generally should be those that can complete the breeding molt early and also migrate early. So the loons that show up first on breeding lakes should be those in good condition. Recent findings have shown us that this group comprises males and females about 8 to 15 years old — the prime of life for a loon. Thus, we predict that the early arrivals are in this age-class. The laggards should be breeders that are either very young — 5 to 7 years old — or very old — 20 years and older. We might expect the territories of such individuals to remain vacant for a week or more after the ice has come off of them.

If age does turnout to be a good predictor of date of territory occupation, then late return from migration could be another source of trouble for an old established breeder. That is, an old territorial bird whose body condition has begun to decline might not only need to worry about being evicted by a young, fit nonbreeder in the midst of breeding; danger might also come from the tardy return of the old bird to its territory in the spring, which could open the door for a youngster to seize the territory, pair with the old bird’s mate, and hold off the former owner when it returns.

I have painted a dire picture. We will have to use the increasingly early ice-outs like this year’s to measure date of return accurately and see if early ice-outs truly destabilize territory ownership. At the moment, I will tantalize you by reporting that breeding success across the population is higher when ice-out comes late. It is speculative at this point, but this pattern might indicate that early ice-outs lead to ousting of old, experienced breeders from their territories, which in turn suppresses chick production of the entire population. If so, I have one more reason to rue early ice-outs!