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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.

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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 goose shot visible in the x-ray.

I cannot think what else to say.

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

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If you feel as though you haven’t heard from me in awhile, it is because I’ve been in the weeds. But my time in the weeds has been fruitful.

I have been analyzing loon reproductive patterns. Specifically, I am investigating what about adult loons themselves and their surroundings leads to success in hatching their eggs. The trove of detailed breeding data we have — 100+ territories followed closely for almost 30 years — gives us a unique window onto predictors of hatching success. I gave a hint of this analysis some months ago. But more data and a refinement of earlier statistics have clarified our understanding and led to new findings.

HATCHING SUCCESS OF MALE LOONS VERSUS NUMBER OF YEARS ON THE SAME TERRITORY. BARS SHOW ACTUAL DATA. CURVE SHOWS RELATIONSHIP BASED ON STATISTICAL ANALYSIS.

One of these findings might be familiar. Males, which choose the nest location, improve in hatching success as their familiarity with a territory grows. This is easy to understand. They use trial and error to find a good nest location. During the first few years on a new territory, they blunder about and lose many nests to predators. Over time, they improve their hatching success by avoiding sites where predators took the eggs. As the predictive curve shows, males make rapid progress in their first year or two on a new territory. Once three to four years have passed, their year-to-year improvement is small.

However, males continue to show incremental — but statistically significant — improvement in hatching success from year to year, even after 15 years on the same territory. Although the annual improvement is slight, it adds up. For example, a male with 20 years on a territory has a 27% better chance of hatching his eggs than a male in his second year. It’s a little hard to imagine the reason for this sustained improvement. Does a male only notice certain biological aspects of his breeding territory through prolonged exposure to them? For example, might a male observe over the course of many years that mammalian shoreline activity is higher at the south end of the lake than the north end and avoid placing a nest at the south end if — say, in his 17th year — circumstances should force him to relocate it? Maybe. In any event, the finding is exciting for the study of animals generally. It suggests that, for an intelligent animal inhabiting a spatially complex territory, adaptive learning — that is, learning that increases reproductive fitness — never really ends.

What about females? Like males, females improve in hatching success over time, but the pattern is completely different. Females have low hatching success in their first year on a territory but improve markedly in their second year. However, they do not continue to improve. Hatching success for females “tops out” after their second year on a territory. The female improvement pattern seems less difficult to explain than the male pattern. Since females do not control nest placement, they do not have any obvious means to get better at hatching eggs as males do. But they must learn something vital about the territory in that first year in order to enjoy greater hatching success in all other years. Perhaps they quickly learn where to forage in that first crucial year and retain that knowledge from the second year on. If so, that important knowledge might allow them to nest more often or better sustain the incubation effort.

HATCHING SUCCESS OF FEMALE LOONS ACCORDING TO NUMBER OF YEARS ON THE SAME TERRITORY. FEMALES HATCH EGGS LESS THAN HALF OF THE TIME IN THEIR FIRST YEAR ON A NEW TERRITORY BUT ENJOY MUCH BETTER SUCCESS IN THEIR SECOND YEAR AND ALL YEARS THEREAFTER.

Comparison of the two figures shows the contrast between males’ steady improvement in hatching success over their entire residency on a territory and females’ one-time jump up to higher hatching success after their initial year.

How can we be sure that the effects I have described are attributable to females’ and males’ experience on a territory instead of merely age? It seems reasonable to hypothesize that adult loons might get better at hatching eggs simply as they gain experience with nesting, regardless of the territory they are on. But this is not the case. I included age as a variable in the statistical analysis, and age turned out to be a poor predictor of hatching success. Thus, a 29-year-old male who loses his territory and settles with a new female on a new territory is right back to square one. He must learn again by trial and error on the new territory where to nest and where not to nest. He is no better off than a five-year-old male that has just settled on his first territory.

What about duration of the pair bond? Since males and females both incubate the eggs equally, they must coordinate their incubation schedules in order to hatch the eggs. So one might have expected that many years of breeding together would translate into greater hatching success for a male and female. But I included duration of the pair bond as a variable in the statistical analysis. Like age, pair bond duration is inconsequential. Yes, males and females that have been together for many years tend to hatch their eggs more successfully than new pairs, but they do so because: 1) the female is past her first difficult year of low hatching success, and 2) the male continues to improve his nest placement over many years on a familiar territory.

Why do I spend so much time making what must seem like fine distinctions? Does it really matter whether old males and females hatch a lot of chicks because they are old or because of experience on a territory? Who cares that old males and females hatch more young not because of more time spent together but because each of them has gained experience with a territory as individuals? We should all care. Since territory familiarity, not age or pair-bond duration, confers reproductive ability upon adult males and females, we should redouble our efforts to ensure not merely that loons themselves live long lives, but that we minimize disturbance to the familiar nesting areas on which their breeding success depends.

Beautiful photo of Clune sitting on his nest by Linda Grenzer.

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The pattern is stark. As you can see from the graph below, loon pairs using artificial nesting platforms have produced a much higher rate of fledged chicks in the Wisconsin Study Area than in the Minnesota Study Area. The pattern was especially dramatic in 2021, when Wisconsin platform pairs reared twice as many chicks per platform as Minnesota pairs. But to compare study areas on the basis of a single year is unwise. Moreover, 2021 was a dreadful year for black flies in north-central Minnesota; most Minnesota nests started in May of last year were abandoned because of the blood-sucking pests. The current year provides a better comparison because flies were not severe in either state. Yet even when we carry out this “apples to apples” comparison by looking only at 2022 data, Wisconsin platforms look far more productive than their Minnesota counterparts. How can this be?

Let’s be very clear on one point. Lake residents in both Minnesota and Wisconsin are moving heaven and earth to help loons. Indeed, folks in both states who float platforms for loons commonly shift them from a first spot to a second and even a third, if doing so keeps nests safe from mammalian egg predators, eagles, waves, and curious humans. It makes no sense to suppose that Wisconsinites are better or more committed platform monitors than Minnesotans.

How then might we explain this curious cross-state disparity in platform success? Perhaps the difference can be attributed to lake size. Since more of the platforms that we study in Minnesota are found on large lakes, the lower rate of fledged chick production from platforms in Minnesota might simply result from higher wind and boat exposure on large lakes, not any state-to-state difference. Lake size, however, cannot explain better platform outcomes in Wisconsin. As the graph below illustrates, the proportion of hatched chicks that actually survives to fledging age is higher in Wisconsin both on large and small lakes. Furthermore, survival of hatchlings is, in general, a bit higher on large than small lakes. So having more large lakes in a sample should increase fledging success, not decrease it.

The new graph does shed some light on the platform pattern. Chicks seem to fledge better in Wisconsin at least in part because more hatched chicks make it to adult size. That is, part of the reason for greater fledging success at Wisconsin platform nests is high chick survival, not necessarily high nest survival.

Could it be that platforms are somewhat overused in Minnesota? In the past two years, 67 of 141 Minnesota nests (48%) but only 43 of 195 Wisconsin nests (22%) have been placed on platforms. Maybe in their zeal to support the state bird, some Minnesotans have lured loons to nest on lakes or parts of lakes that are unsuitable for rearing chicks. At present, this is only one speculative hypothesis to explain the rather low fledged chick production of Minnesota platforms. But it is certainly worthy of investigation. *

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Featured photo by Woody Hagge

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*I must quickly note that most platforms in Minnesota seem well-placed. Some clearly provide loons an opportunity to nest in locations that lack nesting habitat but where food is plentiful. Such locations are perfect for platforms and must help the loon population produce more chicks than it would otherwise.

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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.

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I awaken bleary-eyed after two hours of deep sleep and three hours of tossing and turning. It is time to get up, grab a banana and coffee, choke down my usual peanut butter sandwich, and face the day. I wrap a flannel shirt around my waist — smiling as I recall how my daughter would tsk-tsk at the sight of me — and walk unsteadily down from my fleabag motel in Breezy Point to the convenience store/gas station at the highway intersection where I eat my meals. My whole body aches from lifting and carrying two motorboats in and out of small lakes. My knees are skinned and bruised from squatting for hours on metal boat seats. My hands bear dozens of small nicks and cuts — this one from the Nelson Lake female, this one from the Pelican-Breezy Point chick, this one from nipping myself with needle-nose pliers when closing a steel band on the Star Lake male. My nails are thickly encrusted with the plastic glue we use to seal the bands.

Exhausted and beaten up as I am, I become obsessed with not making a mistake on my trip home. “Don’t forget the blood drops and feather samples. Don’t forget to return the motel room key. Don’t run into a curb and damage the rental car. Don’t leave your laptop in the trunk at the Brainerd Airport. Don’t lose your boarding pass. Don’t forget to text Linda and ask if she can help Molly stow the Loonmobile in Wisconsin.”

I make it to the Brainerd Airport. The Delta ticket agent kindly and somewhat inexplicably checks both of my bulky suitcases for free (!). My Pre-Check status does not show on the boarding passes he prints out for me, though, so I am forced to wait in the security line as passenger after passenger is guided through ahead of me. But at last I am in my seat on the plane. The hardest part of this travel day is over.

At brief moments, I reflect on the past three weeks of loon capture. While most teams have fixed roles for each team member — e.g. Martha runs the motorboat, Steve spotlights the loons, Kevin handles the netting, Emma prepares the bands and data sheet on shore — we use a “musical chairs” model, so that each intern gets a chance to play each role. (The exception is netting, which is tricky to learn and which would cost us many captures during the learning process.) Because of our quirky approach, I as netter am working with a different spot-lighter and different motorboat operator on each lake. This means that I am constantly coaching, constantly adjusting to different spotlighting and boating styles, and all the while just hoping to catch the birds. “Keep the light right in his eyes!”, I whisper. “Lean way forward so that you don’t spotlight the bow!” “Angle the light higher on the water so we can see the loon if it surfaces at a distance!” “Quickly and broadly”, I bleat, after a loon dives right next to the boat, because such a bird could resurface in any direction but will likely be close at hand and easy to see when it does so. “Stay on him!” I cry, helpfully, when a chick dives and swims away but remains within a foot of the surface so that we can track it and pounce when it comes up. Our odds of capture seem long for each loon we spot. Yet somehow, despite our inefficient and high-stress rotation of roles, we manage to catch most of the loons we find. The interns, I learn again this year, pick up each role quickly. They and I are pleased by their rapid improvement. I hope they forgive my occasional impatience during the hunt for each loon. I tell them, “Great work, everybody!” and give an occasional fist bump, when we net a particularly evasive individual. Considering the steep learning curve, they do an amazing job.

In fact, capture went well in both Wisconsin and Minnesota. In large part because of the generous help of Kevin Kenow and his USGS banding crew that spent six nights out, we caught and banded more loons in 2022 than we have in any other year: 94 individuals in Wisconsin and 95 in Minnesota. (Kudos and thanks also to Mike of the National Loon Center and Terri and Richard, NLC volunteers.) We collected crucial mass data from our loons in both states. Comparison of these masses with past years — and with water clarity data from Landsat satellites — might be enough to tell us if Minnesota loons, like Wisconsin loons, have suffered weight losses over the past quarter century owing to declines in lake clarity related to increased rainfall.

We have now caught enough loons in north-central Minnesota that our Minnesota Study Area has taken shape. It includes Nisswa and Pequot Lakes to the southwest, the Whitefish Chain to the north, extends in a northeasterly direction to Outing and Emily, and ends at about the hamlet of Mission to the southeast. In all, the new Minnesota study area comprises some 110 territories. These territories will be those we use to gauge the status of the loon population in north-central Minnesota. These territories will tell us whether Minnesota loons face the same dangers that loons in northern Wisconsin do. I have seen enough similarities between my two study areas that I am concerned. But we must wait to see what the data show.

So as I scrape glue off my nails, rub my sore knees, inspect the healing lacerations on my hands and forearms, and take deep breaths to try to clear my fuzzy brain, I smile. We did well this year. We are well on the road towards assessing the status of loons across the Upper Midwest. And I love my job.

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I have often trumpeted the high survival rate and steadfastness of adult females. Female breeders are masters at perceiving when the tide of battle is turning against them, fleeing from their stronger opponents, and living to breed another day on another territory. Females are survivors.

Male loons, it seems, are not so clever. Perhaps because males control nest placement and, therefore, gain critical familiarity with territories that females do not, males value their knowledge and ownership of a territory highly and seem to fight too hard to hold familiar territories. They often lose their lives as a result.

Against this backdrop of pragmatic, long-lived females and reckless, short-lived males, our capture of a certain male a few nights ago was particularly striking. “Silver over White, Blue over Blue-stripe” first settled on clear, 221-acre South Two Lake in 2002 — when my current field interns were infants or toddlers. The next year, however, Silver over White was booted off of South Two. He settled ultimately on the the Lake Tomahawk-Thoroughfare territory. Thus began one of the most productive runs of chick production we have seen in the history of the Loon Project. Silver over White and two different females reared at least 12 chicks over seventeen years. Moreover, we could hardly help loving this affable male, who year after year nested in plain view and within a stone’s throw of the busy channel that connects Lakes Tomahawk and Minocqua. Dodging indifferent motor-boaters, the Tomahawk-Thoroughfare pair each year led their tiny chicks out of this dangerous channel to the relative safety of the big water of northwestern Lake Tomahawk.

This spring, Silver over White’s second mate apparently did not return. Not missing a beat, he paired with the former female breeder on tiny Schlect Lake — whose mate was also missing — and again nested in his favorite spot along the thoroughfare. Fortune did not smile upon the pair this year, and they did not hatch chicks. When it became too late to nest, both Silver over White and his new mate seemed destined to ride out the year loafing and foraging on Lake Tomahawk.

But Silver over White, who at 25 years of age was well past the time in life that most males look to take a territory by force from another male, was not satisfied with that laidback plan. Instead, he returned to South Two Lake — where we had not seen him since 2003 — and apparently evicted its young owner. (We caught Silver over White a few nights ago, as the featured photo shows.) Silver over White’s feat was especially impressive, because his territorial opponent had two three-week-old chicks and no doubt fought viciously to protect his territory and young.

I returned to South Two today, in daylight, to confirm the territorial situation there. (Marge and Gerry Perner were kind enough to take me out in their pontoon boat.) The scene was chaotic: seven loons socialized distractedly, coming together, splitting apart, and converging again. One fact seemed clear though; Silver over White and a new female — a seven-year-old hatched on Silver Lake, near Minocqua — are the new territorial pair. The freshly-evicted male was nowhere to be seen; we hope he is still alive somewhere. The old female, who was rearing two healthy chicks with the evicted male a few days ago, appears also to have lost her breeding position. As she did two years ago, when she settled on South Two after losing her mate on Little Carr Lake, this female will have to bounce back and find a new place to breed.

Silver over White’s remarkable ability to win a battle against another territorial male at 25 raises two exciting questions. First, how can this male defy the odds and make an aggressive, risky play for a new territory, when most males his age are merely hoping to hang onto their territory for another year or two? Second, it is astonishing and unprecedented to have an adult breeder return to a lake that s/he had been away from for more nineteen years. (The longest stretch of time that a loon had been a breeder on a territory and then had returned to it after eviction had previously been six years.) Did Silver over White try to take over South Two because he still remembers safe nesting sites there and thus knows that he can quickly resume a successful breeding career on the lake? If so, his seizing of his old territory suggests that loons have impressive long-term spatial memory.

I wonder why I have been rooting so hard for Silver over White. I suppose it is because — at a time when I have turned rather silver over white myself — I find it quite inspiring to see his dogged determination to be productive despite the passage of years.

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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.)

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Sometimes on our research project, we observe a rapid series of nasty events that defy explanation and really shake us up.

This happened to my field interns in Wisconsin. They were “roving” outside our normal study lakes, visiting lakes that are either on the fringes of our 110-lake study area or with little past history of supporting loons. On July 8th, Sarah and Claudia found an adult with a fishhook hanging out of its head on the left side, behind and below the ear. Sarah, Claudia, and Chris covered Little Bass Lake on the following day — and found what appeared to be a second loon with the exact same problem.

We have seen dozens of angling casualties at this point, but we had never seen two weird and very similar hookings in rapid succession. Our puzzlement increased one day later, when Claudia was alone on Dorothy and saw a third loon hooked in this peculiar and painful way. (The featured photos at the top are hers.)

When Claudia contacted me and Linda Grenzer and described what she had seen, we had brief paranoid thoughts, “Oh my god; someone is systematically casting at loon’s heads and hooking them!” (Linda tells me this has actually happened before.) Or, on a deeper rung of paranoia: “Someone is capturing loons, sticking hooks in their heads, and releasing them.”

Repeated visits to the three lakes by our team shed more light. When Linda and her husband, Kevin, attempted to capture the hooked Buffalo bird, they did not find it on the lake on one night. Linda and Kevin also observed what they are confident are two different loons with very similar hookings on Little Bass Lake on two separate nights.

Here is what I conclude. First, these are young birds — probably floaters — but clearly not territorial birds with strong ties to these lakes. They are doing what loons do between ages 2 and 7: they are drifting about but staying in the same general area. If you scrutinize the photos above, it seems apparent that the 1st (Buffalo) and 3rd loons (Dorothy) are the same. Each shows a hook embedded in the loon’s head in the vicinity of the left ear, a fishing snap and swivel hanging off of the hook, and no fishing line attached to the swivel. But the feathers obscure the wound itself. On the other hand, the middle photo from Little Bass shows what appears to be open, inflamed tissue, again with a naked snap and swivel dangling from a hook or lure. Linda and Kevin think that the middle loon is certainly a different bird. I think it might be the same bird, even though the wound looks different. Either way, the loon(s) are dealing well with what appears to be a severe injury, because they are flying from lake to lake and intruding into breeding territories (Dorothy), as they should be.

Speaking of coping well with injury, we had another unpleasant angling event in northern Wisconsin during the past week. A male marked by the DNR eleven years ago on a territory near Three Lakes became incapacitated and was taken for treatment by Wild Instincts in Rhinelander. Their X-ray photo reveals the problem — this bird has a treble hook lodged in its gizzard. The bird has bounced back and been released at this point, but the nasty treble hook and attached line is still inside him. (Removal, of course, would have involved extensive surgery likely to harm the bird further.) We can only hope that the male’s digestive system will grind down and pass these hooks eventually, as we have seen in other loons.

In short, loons have taken some hard punches recently, as we have come to expect at this peak fishing time. If they are lucky enough to avoid the death sentence of a swallowed lead sinker or jig, they can be remarkably resilient.