I should have known all along. I should have known last May, when the ancient outboard motor we had just bought to cover the Whitefish Chain spewed a foul rainbow sheen onto the water’s surface and belched a caustic purple cloud that momentarily blinded us. I should have known as I filled huge tanks of gasoline at the Holiday convenience store in Crosslake, hefted them down to the dock, and hooked them up to the belching motor. I should have balked at the absurdity of using a filthy, fossil-fuel-guzzling outboard to study an animal that requires clean air and water.

Instead, I shrugged. “This is how people get around in the Northwoods”, I thought. “This is inevitable. This is the environmental cost of studying loons on big lakes.”

In my own defense, my understanding of proper boating practices became ingrained during my childhood. Back then, when we needed to provision our cottage on an island on 40-mile-long Lake Temagami in central Ontario, we took our little 2-stroke outboard over to the Ojibway Store on Devil’s Island. I still recall taking in the pleasing aroma of balsam fir mingled with mixed gasoline as we listened to the soft lapping of waves against the store’s dock. At the time, my major concern was whether Mom would treat us to Burnt Almond bars when she had finished ordering our groceries. Gasoline was just an innocuous part of the landscape we inhabited.

Indeed, to folks of my generation and generations adjacent, the angry whine of an outboard motor, the slap of a stiff wind in our faces, and the sight of parting, churning waters behind us seem inextricably linked to the pungent smell of gasoline.

But it need not be so. There is a growing market for electric outboards (and inboards) that can replace gasoline motors smoothly and are far cleaner (of course), quieter, and — according to what experts say — very reliable and low-maintenance. I have been researching this.

Why have I experienced this sudden desire to go electric on the water? Two reasons. First, the last two Wisconsin field teams and I faced an absolute nightmare every time we tried to start up our vintage 9-horsepower Evinrude. I did not collect data on our efforts, but I believe we averaged 43 almost-shoulder-dislocating tugs of the starter cord per lake to get that dirty old 2-stroke started. I have had it! (I believe Sarah ’22, Molly, Claudia, Chris, Tia, Bailee, and Sarah ’21 will applaud this move.)

Second, I can no longer deny the obvious. The relentless march of climate change has begun to hurt loons in the Upper Midwest. We can see it in the increase in the May black fly population, which forces loon pairs to suffer horribly as they to incubate their eggs, often to the point of abandonment. And it is even more evident in the sharp decline in July water clarity during the past quarter century (see below) — a decline that impairs loon parents’ ability to find food to feed their chicks. Both increased black flies and decreased water clarity, we now know, come about in large part because today’s warmer, rainier summers produce more flowing water that: 1) supports increased black fly reproduction and 2) washes more matter into lakes that reduces clarity.

So I have finally figured something out that I should have guessed before. Climate change is hurting loon populations in the Upper Midwest in multiple, measurable ways. Cutting back on fossil fuel usage where I can will help slow this damaging pattern. And that is a step in the right direction.

One often hears that clear water is a benefit to loons — if not an outright requirement. The entry for the “Common Loon Habitat” section in Birds of the World, for example, opens with “[Loons] prefer clear lakes….”. The Cornell Laboratory of Ornithology’s page dedicated to the common loon begins with: “The eerie calls of Common Loons echo across clear lakes of the northern wilderness”.

An association between loons and water clarity seems reasonable. After all, loons are visual predators. Why would they spend time in water through which they cannot see?

Yet I learned in Wisconsin in the mid 1990s that loons do not strongly favor clear water. While many of my study lakes, like Alva and Two Sisters, are quite clear and produce chicks regularly, many others, such as Hancock and Oneida, are both turbid and productive. In short, loons in the Upper Midwest thrive and fledge chicks on lakes that vary between 3 and 20 feet of visibility. Indeed a scientific analysis showed that water clarity is not among the factors that dictates use of a lake by loons.

If you think about it, you can understand why a migratory species like the common loon does not overspecialize on water of a certain clarity. As we know from Kevin Kenow’s work, loons fly hundreds of miles across largely unknown terrain and then must land on a waterbody somewhere. If they are in desperate need of a meal at such times — as we might presume — they had better not be too finicky about the menu and the eating conditions. Flexibility must be especially important among juveniles migrating south for the first time, who are crossing terrain that is entirely unfamiliar to them and must find food nevertheless. And, of course, migration begins or ends in the Gulf of Mexico or Atlantic, where both diet and water clarity are entirely different from that during the summer months.

Wait. I posted a blog in the spring detailing the importance of water clarity to loon foraging success and explaining how rainfall was washing material into lakes and reducing clarity to loons’ detriment. Am I now taking that back? No indeed! Water clarity IS important to loon families in July. At that time of year, loon chicks gain mass much faster if the water is clear, and their adult parents maintain body mass better when water is clear. But further analysis has revealed an additional factor that is not so straightforward. I learned just a few weeks ago that loon chicks and their parents actually show lower mass in July in lakes that have high long-term clarity. That’s right; loons have higher masses when short-term water clarity is high but lower masses when they are in normally-clear lakes!

Just to be very plain here, I am saying that short-term water clarity (during the month of capture) increases loon masses because they probably see their food more easily, but some factor related to long-term clarity (how clear the water is on average, over many years) actually makes it harder for loons to put on mass. How do we make sense of this brain-twister?

We can only speculate about the long-term water-clarity-related factor that hinders loons’ foraging. However, there is a prime suspect. Human recreation is strongly correlated with lake water clarity. In other words, people like to spend time boating, fishing, and swimming in clear lakes. During the time when loon parents are trying to stuff their chicks with food, we humans are out there complicating the process by frolicking about in their vicinity. It seems quite plausible that this burst of human activity causes loons to lose precious foraging time and perhaps also access to their favorite foraging spot, if humans are using it. So we can easily see how human activity might cost loons some food and thus reduce mass.

If I am correct that humans impair loon foraging in clear lakes, then we can count breeding on a clear lake as a mixed blessing for loons. Clear water makes food easy to see and catch, but it brings hordes of humans that loons and their young must avoid — which cancels out a good deal of this advantage. Now, if a loon pair were to breed on a lake that had clear water and was inaccessible to humans, they would have it made! Sadly, this seldom happens in our neck of the woods.

In addition to this cool but somewhat distressing news about loon biology, I have distressing and not at all cool news about the Loon Project. We have just lost our primary funding source and are therefore going to be a bit tight for 2023 and perhaps beyond. I am hoping to use a “rainy day fund” to make it through 2023 in Wisconsin. Continuation of the work in Minnesota, which we began only two years ago, is now very much in doubt. If you can consider a donation to help us fight through this lean period — so that we can continue to learn about loon biology in ways that might help preserve the Upper Midwest loon population — we would really appreciate it.

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Photo: The male of the Little Pine-Dream Island breeding pair spent a good deal of time off of the nest in late May of this year, because of black flies. He and his mate fought off the flies, incubated their eggs and fledged two chicks this year. Little Pine Lake, on the Whitefish Chain, is relatively clear, and the male’s purple and white bands are easy to make out.

We all love loons. So naturally we should take any step we can to help them. Right? In that light, artificial nesting platforms (ANPs), or loon rafts, would seem to be a no-brainer. Platforms make it easier for loon pairs to produce chicks.

ANPs fit neatly within the framework of loon conservation. Accepted enthusiastically by most loon pairs, they would seem to provide a perfect, low-cost solution to increase loon populations. They are easy to construct; a person with a modicum of carpentry experience can find plans online and build a platform in a day or less. So platforms provide a simple method by which a single loon enthusiast can improve the breeding success of a pair of loons for many years. Across the loon breeding range, platforms have become a panacea for bolstering reproductive success.

But are nesting platforms all that we need them to be? Now that loon populations appear to be in trouble in Wisconsin and perhaps even in Ontario — and now that some of the causes of declines are beginning to come into focus — maybe it is time for us to step back for a moment. Maybe we should ask whether platforms address the actual problems that loon populations face. To state it technically, can platforms mitigate the specific negative factors hurting loon populations and make populations viable in the long term?

We first need to recognize that platforms address a single, very narrow problem faced by loons. Loon pairs must sit on their eggs — in an exposed location — for 28 days. If a mammalian predator wanders by during that month, the nest is lost. Platforms solve this problem beautifully. They increase the rate of hatching by about 70%. But increasing of hatching success is all platforms do. Platforms put more small chicks in the water — a pleasing outcome for folks that deploy them — but they do nothing to help those chicks reach fledging age. They do not feed chicks; they do not protect chicks from predators. They do not boost adult loon survival. They have no effect on the rate of boat strikes or angling casualties or lead poisonings of adults and chicks. In short, if loon populations suffer declines owing to reduced hatching success, then nesting platforms are just what the doctor ordered. If declines are caused by anything else, then platforms would appear ill-suited to the task.

What do we know at this point about the status of loon breeding populations and factors that might threaten them? Precious little, I am afraid, especially if we are speaking of the entire species range. But we have begun to identify specific threats to loon populations in the Upper Midwest.

At present, the four most significant hazards to loons in northern Wisconsin appear to be: 1) larger populations of Simulium annulus, a black fly that targets incubating loons and causes massive abandonments of loon nests in May and early June, 2) decreased water clarity during the chick-rearing period, which increases chick mortality, 3) increased deaths of adult loons and chicks from ingestion of lead sinkers and jigs, and 4) a mysterious die-off of young adults in recent years that has caused the population of future breeders to plummet. Black fly numbers are highly dependent upon rainfall during the previous year, we have recently learned. More rain means more flies. Increased June and July rainfall also reduces water clarity during the month of July. Both increased black flies and decreased water clarity have become much more severe in the past few decades, probably as a consequence of increased rainfall from climate change. Lead poisoning is known to be a big problem for loons in New England; animal rehabbers in the Upper Midwest feel that lead poisoning has increased in frequency there in recent years. The severity of lead poisoning, of course, should depend upon how much angling occurs and the extent to which anglers switch out their lead tackle for alternatives that are not deadly to wildlife. Finally, we have measured a clear and sharp increase in young adult mortality in our study population in northern Wisconsin. We have no idea, at present, what its cause might be.

How well does the use of nesting platforms to boost hatching success of loons map onto the quadruple threat of increased black flies, decreased water clarity, lead poisoning, and spiking mortality of young adults? With respect to black flies, platforms might mitigate the problem somewhat. Platform-nesting loons suffer abandonments just as severely as do loons nesting at natural sites, but the increased hatching success of second nests on platforms offsets the hit to hatching success caused by black fly-induced abandonments of first nests. Platforms, of course, have no impact on the decreased growth rate and increased mortality of loon chicks owing to declining water clarity and the resultant difficulty of feeding chicks. Likewise, platforms cannot affect the incidence of lead poisoning in an area. And platforms cannot possibly save young adult loons from whatever has caused them to die at such an alarming rate in recent years.

On the whole, then, floating nest platforms do not appear to address effectively the threats faced by loon breeding populations (to the extent that Wisconsin represents loon populations generally).

While that quick analysis might seem reasonable, I have ignored one crucial fact about loon nesting habitat and platforms. Platforms often provide loons with an opportunity to breed in lakes or parts of lakes where they otherwise could not because of the absence or poor quality of nesting habitat. In other words, platforms actually create new nesting habitat. If the new nesting habitat that platforms make available contains enough food that parents can fledge the chicks they hatch there, platforms might provide “bonus chicks” that give the loon population a boost. *

Of course, platforms are so enticing to loons that they must be deployed thoughtfully. A platform placed on a very small lake might lure a pair of loons to use it but result in starvation of the chick(s) because of food limitation. Since a pair lured into such a tragic situation might otherwise have nested and reared chicks successfully elsewhere, such misuse of nesting platforms exacts a cost on the breeding success of the population. (Loon conservationists recognize the pitfalls of using nesting platforms thoughtlessly and only deploy them where they are likely to do more harm than good.)

While loon platforms seem effective at boosting loon populations in some respects but appear ineffective or even harmful in other respects, what conclusion can we reach? Lacking hard data, we can only speculate. However, it is probably safe to conclude that judicious use of nesting platforms in lakes or parts of lakes that lack good nesting habitat adds enough “bonus fledglings” to the population to make platforms an effective conservation tool. Indeed, with the list of threats to loon populations growing, we might soon face a situation where we are casting about for new loon habitats with plenty of food but nowhere to nest — so that we can rely upon platforms to place a good many more chicks in the water.


* Population ecologists will recognize a potential flaw in my reasoning. Even if platforms result in a huge increase in fledged chicks in a population, density-dependent mortality during winter or migration (e.g. owing to food shortage) might wipe out all of these extra individuals. In that case, platforms would not be an effective conservation tool. In fact, increased adult mortality from a variety of causes could produce population decline even in the event of huge “bonus” chick production via platforms.

I am never prepared for chick loss. As a scientist, I know that the first several weeks of life are fraught with danger for loon chicks. Have they developed normally? Can they thermoregulate properly? Are they able to dodge eagles, muskies, and snapping turtles that can devour them when small? Are their parents aggressive and vigilant enough to keep intruders at bay, which might otherwise kill them with a few well-placed jabs? Is there sufficient food in their natal lake to sustain them and support their rapid growth? And these are merely the natural threats to chick survival.

As hazardous to chicks as natural dangers, or perhaps more so, are threats that humans pose. Sometimes these are direct impacts; humans drive their boats rapidly and often strike chicks, which cannot elude them as deftly as adults. Anglers’ lures and baits, recognized as unnatural and avoided by most adult loons, are sometimes gobbled up uncritically by chicks, which are just learning what they can and cannot eat and must gorge themselves in order to grow. The hooks — and especially lead jigs and sinkers that they ingest at such times — pose a grave risk to the youngsters. A more insidious and dire threat that we have seen recently is the decline in water clarity in northern Wisconsin in the past decade, which makes it difficult for chicks and parents to find food and likely explains much of the reproductive decline we have seen there. (We will soon determine whether water clarity is declining in loon lakes in Minnesota as well.)

Although I am acutely aware of the increasing dangers that loon chicks face, I struggle to adjust to the steady drip drip of chick mortality in Wisconsin and Minnesota. When the Rush-USA Point pair lost their chick, I reasoned, “Well, that territory gets high boat traffic; it is hard to keep a chick alive there.” I justified the loss of the Cross-National Loon Center chick and the two chicks hatched by the Rush-Hen pair in the same way. I was a bit numbed by the time I considered the loss of the two young chicks of the Eagle-East pair.

I find it easier to stomach brood reduction. When broods decrease from two chicks to one, I take solace in the survival of the remaining chick. So it went at Upper Whitefish-Steamboat, Ossie-Island, and Sand this year. Very often brood reduction of this kind comes about because food is limiting; the death of the smaller chick actually gives the larger chick a fighting chance to make it.

What stings the most is loss of chicks that have reached four weeks of age. In the past few days, two chicks that had attained this milestone perished in the Minnesota Study Area. (The NLC is awaiting necropsies on both individuals.) Quick inspection of the Lower Hay-Southeast chick that lost its life and washed ashore earlier this week showed what appeared to be traumatic injury on the back, suggestive of a propeller strike. When you consider that the Lower Hay-SE territory is right next to a major public boat landing, this likely cause makes sense. The second deceased chick, from Clear Lake, was 32% lower in mass than its sibling; thus it was falling far behind in acquiring food from its parents. So this looks like classic brood reduction. Indeed, Kate Marthens, one of our Minnesota field team, reported that this chick was not keeping up with its family on the day that it was found dead, an indication that brood reduction was imminent.

The significant increase in mortality of loon chicks of all ages (i.e. both younger and older than five weeks of age) is a hallmark of the current population decline in Wisconsin. I should be learning to cope with it — preparing myself to face it in Minnesota too, if our growing sample there reveals the same trend. But that is more easily said than done. It still hurts like the devil to lose a chick.


Featured photo — One of our largest chicks in Wisconsin is that on Little Bearskin Lake. It was alive and kicking as of this writing! (Molly Bustos, a Wisconsin intern, holds the bird.)

Yesterday, I heard the cheerful, buzzy calls of Japanese White-eyes* flitting about in the trees in my backyard. They are handsome and engaging little birds, but they don’t belong in southern California. They never lived here before humans did. As recently as ten years ago, white-eyes were quite difficult to find in the area.

A few weeks ago my wife, son, daughter, and I visited my ailing mother in Houston. On our first morning there, we were awakened by the incessant cooing of White-winged Doves*. They too are a striking species. The flashy white stripes on their wings and tails set them apart from the more familiar and homely Mourning Doves. Even the ceaseless calling of White-wings is rather pleasant. Don’t trust me on this; the abundant murmurings of this species inspired Stevie Nicks to write an entire song about them. But White-winged Doves have not always lived in the Houston area. I remember scouring trees around the Galveston County Courthouse in vain for this species with my mentor, Fred Collins, on a Christmas bird count a half century ago.**

Of course, while new species colonize new regions; well-established residents also vanish. In the Upper Midwest, the Piping Plover, a cute little shorebird, has recently become severely threatened. Though I have never seen a Piping Plover in all my years in Wisconsin and Minnesota, I do have experience with a second threatened species, the Black Tern. These agile fliers flit about marshy areas, plucking insect larvae and small vertebrates from the water and vegetation. They are appealing birds — with jet-black bodies that contrast tastefully with greyish wings and tail. But it is a longshot to find them in the Upper Midwest nowadays. What seemed a healthy breeding colony fifteen years ago on Wind Pudding Lake in northern Wisconsin — where we have always had a breeding loon pair — has disappeared altogether. It has been so many years since I last saw Black Terns on Wind Pudding that I have stopped looking for them there.

In short, my years as a bird-watcher have taught me that populations of birds change dramatically over time. Some species magically appear in new places, and other species disappear. I suppose it is my first-hand experience with the dynamics of avian populations that infuses my current research on loon populations in Wisconsin and Minnesota with such urgency. This is why I sweat the black fly season in May and June, worry about boat strikes and lead poisoning, and am in a bit of a panic over the recent loss of water clarity in the region. I have now seen — as I had not in 1993 when my loon work began — that birds can disappear.


* Photos by Natthaphat Chotjuckdikul and Ted Bradford from eBird.

** In fact, the picture is a bit complicated in the case of this species. White-winged doves occurred commonly in the southwestern U.S. 100 years ago, but the population was devastated by the expansion of the citrus industry. However, in the past three decades, the species has begun to nest in citrus trees and has come roaring back.

The beginning of the tale is heart-rending. A gosling is orphaned before hatching. A loon pair fails to hatch chicks of their own and, seeking to fill the void, sits on eggs they find near their nest. When these two desperate parties converge into a single — if nontraditional — family, they produce a heart-warming story*.

To see two species coexist despite 90 million years of evolutionary time spent apart is surprising. To see them not merely tolerate each other but become thoroughly interdependent, as parent and offspring, is truly striking. Such an improbable scenario makes one hopeful. This story suggests that differences between groups — even vast ones such as between geese and loons — can be overcome.

On the other hand, the sight of a gosling nestled comfortably on a loon’s back is also strange. It is a reminder — like exploding black fly populations, loss of water clarity, devastating storms, and the sudden abundance of wake boats — that the loon’s world has changed.

*Thanks to photographer Brad Thompson, who shared his beautiful photo.

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I love the painting because it is not about loons. John Seerey-Lester’s artwork*, pictured above, is about rain. The painting recalls those moments when you were out on a lake — taking in the vast expanse of its surface; gazing at an eagle circling high above; or watching a loon pair drift by with their four-day-old chick — and a rogue cloud emptied upon you. Most of us who have ventured out onto lakes can recall such an experience. In the moment, there is panic: a hastily zipped jacket, a vain attempt to find some form of shelter to thwart the impending deluge. But there is wonder and beauty in the storm itself. As Seerey-Lester’s painting shows, raindrops transform a lake’s monotonous surface into an astonishing palette of dancing splashes. Accompanied by a soothing whisper, the spectacle of a rainstorm on a north-country lake is one of nature’s wonders.

Loons cope well with rain, of course. What harm is more water, after all, when you live in water? Like most birds, loons assiduously preen their feathers, coating them with oil from a gland at the base of their tail, so water beads up on their heads and backs, but ultimately rolls harmlessly off them — like water off a loon’s back. A downpour might necessitate a few shakes of the head, inspire a few extra wing flaps, and prevent foraging for a time, owing to reduced visibility. But loons greet rainstorms with little more than a shrug.

Considering the grace with which rain appears in loons’ lakes — and, of course, its fundamental importance in supporting all life — I was unpleasantly surprised to learn this week that rainfall has likely contributed to the reproductive decline of loons in northern Wisconsin. You see, rain does not merely stimulate plant growth, raise water levels, and rinse car windows. Rainfall also washes all sorts of matter into lakes. This includes visible organic matter such as sticks, leaves, and soil but also invisible nutrients and chemicals. Many substances that reach lakes via rainstorms reside naturally in soils or on the forest floor. Others, like fertilizers and sewage, have been added by humans to the environment. Human-added materials that contribute nitrogen and phosphorous to lakes can cause populations of phytoplankton to surge, which reduces water clarity.

And this brings us back to loons. Loons rely strongly upon their vision to catch fish and other prey underwater. As our recent investigations have shown, reduced water clarity hinders loon foraging. We now know that reduced water clarity leads to poorer body condition both in breeding males with chicks and in chicks themselves. The decline in chick body condition and accompanying rise in chick mortality are essential components of the breeding decline now underway in northern Wisconsin.

Water clarity in loon breeding lakes in July declines with increased rainfall in June and July.

Why am I so determined to blame it on the rain? Because a few days ago I examined water clarity estimates from my collaborators — Kevin Rose and Max Glines of Rensselaer Polytechnic Institute — and found that water clarity in July, the best predictor of adult male and chick mass, is, in turn, strongly dependent the amount of rainfall in June and July. Just as April showers bring May flowers, June and July showers bring July algal blooms in Wisconsin lakes that make it more difficult for loons to find their prey.

Of course, rain itself is not the true villain. Rather it seems to be fertilizers, leaky septic tanks, and maybe even pet waste that human lake residents have added to the ecosystem that are contributing to the loss in lake clarity.

You might wonder if there is truly a sustained, irreversible downward trend in water clarity or whether water clarity fluctuates according to natural cycles and is merely on a downward trend at the moment. If we are simply on a temporary downward trend, then it is a decade-long trend, according to Max and Kevin’s measures of water clarity (see graph just below).

Moreover, as I reported recently (see graph below), loon males have been losing body mass for the past 30 years. So the data we currently have indicates that we are on a prolonged downward slide with respect to both water clarity and loon mass.

Male loons have been gradually losing body mass for the past 30 years; female loons do not show such a decline.

So what do we do? All hope is not lost, I think. But if our data and interpretation are correct, then we must immediately begin to monitor — and curb — chemical runoff from shorelines into lakes from sources such as fertilizers and septic systems. In the long-term, we need to understand that summer rainfall will only increase as the Earth continues to warm and cloud formation accelerates. In short, it is a bit harsh to blame the rain for loons’ current reproductive woes, but increasing rainfall in coming decades will probably push us more rapidly in the wrong direction.

*”Sudden Rain”, copyrighted by Sir John Seerey-Lester