Ensconced as I am in the endless summer of southern California, it is easy for me to forget what loons are facing. As we know from Kevin Kenow’s excellent work, about half of all adults have now left their breeding lakes in Minnesota and Wisconsin and are on their way southwards. Many of these birds are hanging out in the Great Lakes before making the long overland journey to Florida. Some adults remain faithfully with their chicks, hoping to stuff a few extra fish into them before abandoning them to their own devices.

Adults’ departure leaves only chicks on the breeding grounds. Thanks to the the work of our fall observation teams and Brian Hoover, who pulled the data together and wrote it up, we know that most juveniles leave their natal lakes in the fall but hang out nearby. They search diligently for large, food-rich lakes, especially favoring those that resemble their natal one in pH. Their strategy is clear. First, stuff your face with fish where they are abundant and similar to the ones you first learned to hunt. Next, wait until the last possible minute to build up your energy stores. Finally, bolt for Florida before the ice makes it impossible to take off.

The juveniles’ plan has a touching pragmatism to it. There is no subtlety. Birds of the year are not burdened with territorial responsibilities or pangs of parental guilt. They just wish to survive long enough to reach the wintering grounds. And, generally speaking, they do.

But a few get left behind. Thus it happened with the Lake Thompson juvenile this fall. A great strapping youngster when we caught him in late July at five weeks of age, he continued to grow and thrive in the 12 weeks since we last saw him. Ultimately, he had no more need of his parents and moved five miles west to Boom Lake in Rhinelander to fatten up for migration. There, however, he ran afoul of a reckless hunter. Linda and Kevin Grenzer caught him last night and quickly saw that his left wing was fractured. X-rays at REGI confirmed the break — caused by lead goose shot visible in the x-ray.

I cannot think what else to say.


Top photo by Linda Grenzer. X-ray by REGI staff.

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.

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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What if we had an early warning system in loons that could alert us to population decline, like the proverbial canary in a coalmine?

Male loons might serve as such an early warning system. That is, careful monitoring of the health of male loons might provide a good indication of the health of the loon population as a whole. How is this possible? Because the more we study the breeding ecology of loons, the more stark differences we find between the sexes. And — more to the point — male loons have some chinks in their armor that females do not.

Most fundamentally, males are 25% larger than females. Greater size places greater energetic demands on males. Males are living “closer to the edge” than females and might often fail to acquire enough food during the season to maintain good body condition. Thus, a decrease in the quality or quantity of food — which could set in motion a population decline — should strike males first and hardest. Indeed, as the graph below shows, the average mass of male loons has declined in northern Wisconsin over the past 30 years in a way that suggests they are having more time finding food now than they used to. (Note that females have not declined in mass during the same period.) The obvious conclusion: something in Wisconsin lakes has changed in the past three decades that has impaired males’ ability to feed themselves.

Average masses of male and female loons in northern Wisconsin, 1991 to 2021. Male mass has declined significantly during this period, while female mass is unchanged.

Long before I discovered that male masses were in decline, I had begun to worry about male loons. You see, male loons live shorter lives than females. This means that there are simply fewer adult males around. In fact, the majority of non-territorial adults (“floaters”) in the loon population are females. Since males are in short supply, the loss of an adult male breeder on a lake or territory sometimes leads to that territory becoming vacant. In fact, in 23 of 24 well-documented instances where an adult breeder’s death was associated with a territory vacancy, the dead breeder was a male. Vacant territories are, of course, a harbinger of overall population decline.

Sadly, recreational fishing does not help the situation. Possibly because males’ greater size makes them a bit more desperate to feed themselves, male loons are twice as likely as females to be hooked by anglers or become entangled in fishing line. This pattern is well-documented in New England loons, but the same scenario plays out in the Upper Midwest. Specifically, of 47 known fishing entanglements among our study animals, 33 involved males, and only 14 involved females. Angling mortality, then, exacerbates what is already a female-skewed sex ratio owing to early male senescence.

It is difficult to predict the future, but I think you can see why I am concerned. Male loons appear to be in trouble. We cannot say for certain whether mass loss by male loons will cease or continue. Furthermore, we have no evidence to date that the 4% net loss in mass by males since 1991 has negatively affected their survival. So it is too early to panic about these patterns. But it is also hard not to feel like a miner glancing anxiously at his lethargic canary.

He was the biggest, healthiest juvenile we caught in Minnesota last year. The Rush Lake-Northeast chick was so independent on July 16th, when we first attempted to catch the family, that we could not relocate him after capturing and banding his parents. We shrugged, returned the following night, and had better luck. At 2900 grams, “Copper-White”, as he became after banding, was 300 grams heavier than the second-heaviest chick we caught last summer and almost certainly a male.

Considering the risky environment inhabited by juvenile loons, it is a mistake, I have found, to become attached to them. So, with the exception of the “Miracle Chick” — a juvenile on Squash Lake in 2012 that lost his father at three weeks, watched his mother quickly re-pair with a new male, but still got enough food and attention to fledge — we have tried to avoid this practice. Still, Copper-White became lodged in my mind. I had great hopes for him. If any juvenile had a chance to fledge, migrate, and come back in a few years as an adult, it was Copper-White.

Large size and good body condition, it seems, are not enough to protect a loon in his first few months of life. Last Friday, the National Loon Center got a report of a loon hemmed in by ice on on Cross Lake. They raced out to check the bird, and Mike Pluimer snapped the photo above.

It was alarming enough to hear of a loon still on the breeding grounds in mid-December. By this time, loons from the Minnesota population should have arrived in Florida and begun adjusting to a saltwater diet. Our hearts sank a bit further to see the bird’s plight. Resting in a tiny pool of open water surrounded by encroaching ice, this juvenile was clearly in dire straits. Why had he failed to migrate south with others of his species? Something must have gone horribly wrong.

Following heroic efforts on the part of the Crosslake Fire Department, Copper-White was caught and transported to Wild and Free Rehab Center in Garrison. Terri and Richard, who live on Rush Lake and watched the chick grow from its earliest days, reported that the captured bird was strangely docile — another worrisome sign.

Arrow points out where Copper-White’s right wing was sheared off at the metacarpal bone by a boat propeller. (Photo courtesy of Wild and Free Rehab, Garrison, MN.)

It took little time for Katie, the vet at Wild and Free, to diagnose Copper-White’s problem. The end of the loon’s right wing had been sliced off some time ago by a boat propeller, rendering him incapable of flight. Unlike many hawks and owls, loons’ size and need for open water make them impossible to keep alive in captivity. The only option was to euthanize this bird.

Alas, I have no cheerful anecdote to cushion the blow. We are disheartened to lose a healthy, strapping juvenile loon to a boat strike. But boat strikes that injure loons are a fact of life in the Upper Midwest. We lost a healthy adult male even more tragically two years ago in Wisconsin. The only comfort here is that boat strikes occur infrequently enough in the Upper Midwest that they do not contribute meaningfully to loon mortality. At the moment, that is cold comfort.

Although most of our research team is long gone by September, Linda and Kevin Grenzer remain in Wisconsin. At a time of life when most folks widen the dimples in their BarcaLoungers, these two are devoting their time to rescuing injured birds. (Linda, of course, is also one of our field team members and a gifted photographer to boot!)

Linda and Kevin have gotten more proficient at rescue in recent years. Four years ago, they often found themselves hours from home on some false alarm — an eagle that was heat-stressed but recovered; a loon that seemed wounded but was merely preening. These days they insist on seeing photos or getting vivid descriptions of injured birds from experienced observers before setting out to save them.

After Ken and Joanne Lubich sent us the photo at the top of the page, it was clear that a bird was in trouble. The Lubiches keep a close eye on the two loon pairs on eyeglass-shaped Two Sisters Lake. On a routine patrol around the lake on September 13th, they were horrified to see that one of the two strapping chicks on the east lake had a huge muskie lure attached to its left leg and was swimming erratically.

It might seem difficult to find the positive here, but, in fact, this chick was fortunate. The Lubiches keep a close eye on the loons on Two Sisters and have a network of contacts who live on the lake. Thus, the distressed chick was found only a day or so after being hooked. Furthermore, Joanne and Ken know Linda and Kevin and immediately reported the hooked bird to folks who could help it.

Once they made it to Two Sisters yesterday, Linda and Kevin were able to capture the distressed chick, when it ventured close to shore. A quick inspection told them that at least two of the hooks on the lure had punctured the chick’s foot tissue and become infected. They decided to transport the bird to REGI for treatment.

As is evident from the photo below, we had captured and banded this chick. On the night of capture, July 13th, the bird weighed 2460 grams. Yesterday, the chick weighed 2470 grams, which means that it was only 10 grams heavier yesterday than it had been two months before. This tells us that the bird has lost a great deal of weight — perhaps 500 to 600 g — owing to the hooking. Needless to say, loons go downhill quickly when they are prevented from feeding themselves. This bird probably fed little or not at all for six days.

The world is looking brighter for this chick. Multiple hooks were removed from its foot. One hook was too close to a bone to remove and had to be left in the bird. (REGI staff hope that swelling in the foot will push the hook out in time.) If its injured left leg recovers, and it becomes fully mobile again, the bird will be released in a few days back on Two Sisters. Meanwhile, this loon is taking full advantage of the favorable fishing conditions provided in its temporary home!

In a recent post, I described how the popularity of loons and the willingness of many folks to pontificate about them without solid data or thoughtful scientific analysis makes loons unique. I tried to point out that this practice can be harmful, if we make misleading statements about loon conservation at a time when some loon populations are declining.

Now, let me give an example. Millions of state and federal dollars have been spent in recent decades in attempting to measure the effect of methylmercury (the toxic form of mercury) on wild animals, especially birds. Without a doubt, more funds have been spent analyzing mercury impacts on loons than on any other aspect of loon biology. What have we learned from this body of work? The major take-homes are that: 1) mercury certainly can affect behavior and survival of adult loons and chicks if it occurs in a high enough concentration in their tissues, 2) high mercury levels tend to occur mainly in loons living on small, acidic lakes, which have negative effects on loons that have nothing to do with mercury, and 3) harmful concentrations of mercury do not occur in most geographic areas within the breeding range. In short, despite an abundance of research and the expenditure of millions of research dollars across three decades, we have no direct evidence that mercury negatively impacts loon populations. In fact, the consensus among loon scientists is that mercury probably has little or no negative impact on most populations.

The situation is dramatically different with lead. Careful analysis of loon carcasses in New England has shown us that lead is quite deadly and affects a great many loons. (The featured photo above shows a deadly lead sinker in the stomach of a loon that died a few days ago in Wisconsin. Photo by Wild Instincts.) In a 2017 study, Grade et al. determined that a whopping 48.6% of the loons they examined had been killed by lead sinkers and lures. The authors estimated that this mortality rate had reduced the New Hampshire loon population by 43%.

The contrast between mercury and lead is stark. Mercury might affect loon survival and breeding success slightly in a few isolated populations. Lead has been shown to cause half of all loon deaths in one state and to make an enormous dent in the loon population of that state.

The contrast between these two toxins goes further. Mercury exposure is pushed to high levels mainly through burning of fossil fuels like coal and oil, which contain mercury. So reducing loons’ exposure to mercury requires a long-term effort to reduce burning of fossil fuels over a large geographic area. In contrast, loons are exposed to lead through our use of lead sinkers and fishing lures. The remedy for lead-related loon deaths is simply to implement use of lead-free fishing tackle in lakes where loons breed. (Steel, tin, and tungsten are common alternatives). Indeed, lead bans are now in place across New England.

Here is the problem. Despite the lack of evidence that mercury affects loons in nature, mercury has become the “go-to” environmental toxin mentioned by many loon researchers. Mercury has become such a prevalent scapegoat in grants, reports, and even published papers that many of us are not keeping its limited impact on loons in proper perspective. A clear-headed, candid, objective review by a loon researcher with a strong background in mercury toxicity would do wonders for loon conservation. At a time when studies have just reported long-term declines in two loon populations, those of us trying to conserve loons would do well to focus our attention on the real enemy.

We have been out all night for the past week capturing and marking adult loons and chicks. It is tiring work. Last night, for example, we had to carry our 14 foot motorboat off of a highway shoulder and into Sunday Lake. Next, we hefted it down a long flight of steep stairs, out a long narrow dock and into a marsh to reach the Minocqua-Huber Bay territory. My back still aches! But these visits were productive. In both cases, we captured a male hatched in the study area, his unmarked mate, and their two chicks. So our strenuous efforts were rewarded. (The Sunday male is a fifteen-year-old who was hatched on Seventeen Lake; the Minocqua male is only six and was reared on Brandy Lake.)

Our third lake of the night has a public landing. It was a breeze to back the trailer up and slide the boat into the weedy, pike-rich waters of Little Bearskin Lake. For a change, we were not sweating profusely and breathing hard as we began our improbable search for the pair and their young. However, we were not prepared for what we discovered.

The visit began routinely. We motored slowly to the middle of the lake to listen for the birds, as we often do. Within a minute, a bird wailed in the southeast corner. We were thrilled, because we seemed to have found the family quickly. The loon that had called was, in fact, only the female from the pair, who had wandered off separately from the male and chicks. Nevertheless, she responded strongly to our chick calls and was easy to scoop out of the water. As we removed her from the capture net, we were alarmed to find that she had a fishing lure and monofilament line wrapped tightly around her left leg.

Fishing line is unkind to wildlife. The very properties that make it attractive to anglers — its strength and thinness — give fishing line the ability to cut deeply and mercilessly into the flesh of animals unfortunate enough to become entangled in it. As the photo above shows, the female’s left leg was tightly wrapped, and a lure and hook had become attached to her leg.

Linda was able to cut away the line that had pierced the scaly, keratinized outer layer of the female’s left leg (see video below) and remove the attached lure. We are concerned about the raw tissue that was exposed by this piercing, but Linda applied antibacterial ointment, and we are hopeful that she will recover.

An injury to any loon is painful, but this one was doubly so. This mother of two chicks is the second oldest loon in our study area. She is at least 31 years old! First marked in 1996 on West Horsehead, she raised 19 chicks with three different males on that lake but was evicted in 2018 and fell off of our radar. We were delighted to see that she had resettled on the very productive Little Bearskin territory this spring with the 18 year-old male there. The two healthy chicks she has raised with him provide further evidence that females retain the ability to produce young during their later years.

But we worry. At 3500 grams, she is 250 grams or so lighter than when we captured her several years ago. This, the fact that she had left the male to care for the chicks last night, and the odd not-quite-wails that she uttered after we released her might indicate that she has been compromised by this angling injury.

In fact, she and we were extraordinarily lucky. Most “off-chick” adults — those not tending their chicks — are difficult to find at night and capture. Only the fact that we stumbled into her before we found the male and chicks allowed us to catch her, free her from the tightly-wrapped fishing line, and treat her injured leg. Now, at least, she has a fighting chance to resume her parental responsibilities, regain lost weight, return to her Florida winter quarters — and perhaps return again in 2022.