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I did my graduate work at the University of North Carolina-Chapel Hill. My advisor and I spent tooth-chattering mornings from November to April sitting in blinds and watching 300+ color-marked white-throated sparrows compete for seeds at feeding stations. We learned a good deal from this work. We now understand how aggressive behavior affects the survival and local movements of this species.

Many lake residents and outdoorsy types in Wisconsin and Minnesota recognize white-throated sparrows from another time of year. These striking little birds sing distinctive, whistled songs in late May and June along forest edges in the Upper Midwest. Although they are more understated, the calls of white-throats typify northern boreal forests much as loons’ calls symbolize northern lakes.

White-throated sparrows live two very different lives in summer and winter. We witnessed part of the transition between these lives in North Carolina. During early May, the undisciplined hordes of sparrows we had grown accustomed to seeing broke up into smaller flocks. In mid May, they spurned the seeds we offered and fed instead on protein-rich buds they found in treetops. By late May, our sparrows had left for the north country.

The departure of our study animals left us with mixed feelings. On the one hand, it gave us a much-needed break from the daily grind of field work. On the other hand, it left a void and a puzzle. Where had our birds gone? Were they New England breeders that serenaded summer hikers in the White Mountains of New Hampshire with their plaintive calls? Or had they headed inland towards the Upper Great Lakes where they crooned to cottagers on lakes? Perhaps they had ventured to northern Ontario, Manitoba, or even the Northwest Territories. If so, they likely belted out their songs with no human around to enjoy them.

I spent many hours pondering summer destinations of our wintering sparrows. I felt — quite irrationally — that there must be some way to learn where they migrated to breed. Could some distinctive wisp of vegetation or a sticky residue from berry or insect from the breeding quarters become lodged in their feathers or stuck to the bill; survive the journey southwards; and still be detectable in North Carolina in October? Perhaps. But no researcher, to my knowledge, has ever determined the migratory origin of a small songbird by such a means. Eventually I gave up on my fanciful notion of learning where our sparrows spent the six months when they were not in our company.

Other scientists did not give up on the dream of linking breeding and wintering areas. Indeed, for a few decades now scientists have used stable isotope analysis to detect geographic movements of itinerant animals. Stable isotopes are different versions of a chemical element with different masses. For example, most hydrogen atoms (over 99.9%) occur as H-1, which has no neutron in the nucleus. But a few hydrogen atoms take the form of H-2, which possesses one neutron and weighs twice as much. Here is the key point: water droplets in rainfall in each geographic region contain a characteristic tiny percentage of H-2 (.02% in one place, .008% in another). And living things absorb water so that they too contain a ratio of H-2 to H-1 in their bodies that is distinctive to the region they inhabit.

Measurement of stable isotopes is especially useful to bird biologists because of feathers. Feathers are not living tissue. They are keratinized structures that grow from living tissue and, once formed, no longer receive a blood supply. So the stable isotope ratio within feathers does not track the current environment like that in skin, blood, or muscle. Instead, feathers are a time capsule that contains the stable isotope ratio at the time and place of their formation. When a bird grows new feathers in one place and migrates to another, its feathers retain the stable isotope signature of the molting location.

Loons grow fresh wing feathers on the wintering ground prior to migration. This means that wing feathers of breeding loons bear the isotopic signature of their winter quarters. Thus, a small wing feather we clip in July can tell us where a specific breeder spends its winters.

We have some understanding of loon migration and wintering patterns, thanks to the work of Kevin Kenow, Jim Paruk, and their co-workers. Furthermore, recoveries of banded loons have helped us sketch out the wintering range of our Wisconsin and Minnesota breeders (see map below). However, we cannot tell where any particular loon — like the territorial female on Roosevelt-Southwest — winters.

Sources and destinations of loons banded in Wisconsin and Minnesota. Light blue lines are paths of adults; dark blue lines indicate first-winter birds.

Why does it matter where a specific territorial loon spends the winter? Because we have burning questions about conservation of Wisconsin and Minnesota loons that require fine-scale understanding of migratory patterns. For example, does use of certain wintering areas lead to low survival for Upper Midwest breeders? Do poor years for adult returns in Wisconsin and Minnesota correspond to “die-offs” in specific wintering areas? Does the low annual return rate of adults in Minnesota (compared to Wisconsin) indicate unfavorable conditions in their more westerly winter range (see figure above)?

In fact, we have many more questions of this kind. To answer some, we will need ecological data from the Gulf of Mexico and Atlantic Coast. At the moment, however, subtle information locked within the feathers of our study animals and transported by them from wintering to breeding grounds is giving us hope that we will soon have a better understanding of common loon survival throughout the year.

Thanks to Linda Grenzer, who took the cool photo of the male from Halfmoon Lake coming in for a landing some years ago.

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When humans search for answers to complex problems, we often spend a good deal of time casting about in the dark. And our quests for answers commonly conclude with limited success or total failure. At least that is how it goes for me.

I suppose my quests are nerdier than average. In my research, I try to answer questions like: “Why do young loons seek to settle on lakes that resemble their natal one?” or “Why do female loons not yodel like males?” Still, the vexing puzzles I face in my work are not wholly different from the gnarly ones I confront in everyday life. “Why does the cupboard door under the sink never close properly?” “Why do plants keep dying in the southeastern corner of our yard?” Regardless of their origin, life is full of riddles that are challenging to address — and rewarding to solve.

This fall, I have been investigating factors that influence masses of adult loons and chicks. Most predictors of adult male mass* are easy to understand or, at least, lead to highly plausible and testable hypotheses. Males show a long-term decline in average body mass that began thirty years ago and continues today. This result suggests that human encroachment of some kind has made it harder for loons to maintain optimal body condition — and is getting worse. Recently we also found that adult males have lower mass on territories with a high density of docks. Again, we can understand how more docks — and more angling — might hinder adult male foraging and lead to lower mass.

Likewise, most predictors of chick mass are easy to explain. Short-term water clarity affects chick mass strongly. We have known for over a year that lower aquatic visibility hinders loon foraging. And I was not surprised to learn that a chick’s mass is correlated with that of its mother. It stands to reason that body size would be heritable in loons, as it is in other species. Finally, like their parents, chicks show a long-term downturn in mass over three decades that hints at environmental degradation. These three statistical relationships make perfect sense.

In fact, a brain twister did not emerge from this recent analysis until I looked at the relationship of dock density and chick mass. You see, chick mass is positively correlated with dock density. That’s right: the more docks there are on a lake’s shoreline, the fatter the local loon chicks become! The result is astonishing for two reasons. First, it runs counter to logic; second it is opposite to the male pattern. How could more docks — and thus more boaters and anglers — help chicks gain mass, when the same factor is harming their male parents?

I checked and double-checked the statistics. I scanned the data for abnormalities. Many days of fruitless pondering passed. At last I hit upon an idea that was hiding in plain sight: maybe the anomalous pattern had to do with food. Now, the data on fish abundance in our study lakes is of poor resolution and contains many holes. In fact, there are not enough data from any of our 205 Wisconsin study lakes to compare fish abundance with chick mass directly. Still, scientists have collected reams of data on abundance and size of fishes statewide. So we know a good deal about broad patterns.

A recent long-term analysis of fisheries shows that small fishes favored by loons — bluegill, yellow perch, crappies — have been declining in average size across the state for 70 years. The decline in panfish sizes — a consequence of overfishing, according to fisheries biologists — provides a plausible explanation for the long-term loss of mass in adults and chicks. Loons, it seems, must work harder each year to capture enough panfish to sustain themselves. This broad decrease in panfish size in Wisconsin lakes, therefore, might explain why masses of chicks and their male parents have declined in recent decades.

But how do we explain why loon chicks gain mass in busy lakes while males lose mass? Remember, when young, chicks can only swallow very small fish (as Linda Grenzer’s photo shows). Even at five weeks, chicks consume fish smaller than those that adults do. This appears to be the key point. Young chicks ingest small fishes — the very size-class of fishes that thrives when larger fishes are removed from the lake by anglers.**

So I have solved a puzzle related to loon feeding ecology. Well, more accurately, I have generated a highly plausible hypothesis that is consistent with the data but will require further testing. For the moment, I am quite satisfied with this outcome. Because I am a scientist, and that is how we roll.

*We have a large sample of males than females, so our analysis of male mass is more robust.

**While we might celebrate that young loon chicks appear to benefit from human overfishing, this news is not cheering. The first five weeks of a chick’s life, after all, is only one critical phase that it must pass through. This year’s hatchlings are 13 to 18 weeks old now. Their diet is now identical to their parents’. Like their parents, 2023 juveniles are finding fewer large bluegills, perch, and crappies. So they too must spend more time foraging than they did 30 years ago. Could the dearth of large panfish on the breeding grounds help us understand why loon survival from the late juvenile stage to adulthood has declined precipitously in the Upper Midwest?

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Many of my colleagues fear ChatGPT. They fear that students will use this new online tool based on artificial intelligence to generate papers and answer questions on homework assignments that students are meant to tackle themselves. Their fear is legitimate. Why? Because if you read ChatGPT’s answers to a range of questions, you notice something rather quickly. ChatGPT generally produces plausible, thoughtful, coherent responses. Furthermore, ChatGPT writes well — at least compared to what I see from most of my undergraduate students. In short, ChatGPT creates headaches for instructors. It is forcing us to reconsider how we evaluate our students.

On the other hand, I was excited to learn what this new AI tool would produce when asked about loon biology. I asked ChatGPT: “Do loons mate for life?”. It responded:

While common loons often return to the same breeding territories and may reunite with the same mate from the previous year, these pair bonds are not necessarily permanent. After the breeding season, loons typically migrate to coastal or open water areas for the winter, and their social behavior can be more flexible during this time. When they return to their breeding territories in the following spring, they may or may not reunite with the same mate.

Now, this is not a terrible answer. ChatGPT is correct when it suggests that loons do not mate for life. But its mention of migration is off-topic. Its point regarding “social behavior” during winter is irrelevant. Its statement that loons “may or may not reunite with the same mate [in the spring]” is grossly misleading. And ChatGPT has entirely failed to mention the chief reason why loons do not mate for life: territorial eviction.

ChatGPT’s responses to loon-related questions are similar to its answers on other topics. The program searches the web for information from which to build its responses. But because these responses draw information from countless online sources, they include the good, the bad, and the ugly. In short, ChatGPT gives you a blur of “conventional wisdom” about any topic, not rigorous and precise scientific truth. Its answers are, for the most part, uncontroversial, vague, and riddled with caveats.

I turned my attention to loon conservation. When I asked, “Are any common loon populations in trouble?”, ChatGPT came back with:

As of my last knowledge update in September 2021, the status of loon populations, particularly the Common Loon (Gavia immer) in North America, varied by region and was a subject of concern in some areas. Common Loons were classified as a species of “Least Concern” by the International Union for Conservation of Nature (IUCN) due to their relatively stable population at the global level.

However, it’s important to note that local and regional populations can face significant challenges, including habitat loss, water pollution, lead poisoning from ingesting fishing tackle, disturbance from boating and recreational activities, and climate change impacts on their breeding and wintering grounds. These factors could affect specific loon populations and lead to localized declines.

ChatGPT is spot on in some respects. Loons are in no trouble globally. And the status of populations varies from one region to another. But the program uncritically lists many anthropogenic factors that might harm loon populations and provides no specific information. One might infer from ChatGPT’s statement that we must solve all of the problems listed in order to preserve loons. Or perhaps loon populations face many obstacles but none is severe enough to cause serious harm. In truth, we do not know which, if any, of the listed factors might endanger loons. Furthermore, ChatGPT has failed to mention two factors — exploding black fly populations and decreased water clarity — known to harm loon populations in the Upper Midwest. If this had been a class assignment, ChatGPT would have earned a “C-“.

ChatGPT’s take on factors threatening loons sounds eerily familiar to what we loon conservationists often say. (I include myself in this group.) That is, we often settle for a ChatGPT-caliber pronouncement about loon conservation. We say or imply that if we: 1) enact a lead ban, 2) reduce human settlement on northern lakes, 3) eliminate water pollution, 4) keep boaters away from adults and chicks, and 5) halt climate change, then we can save loons. These goals, of course, range from difficult to impossible to achieve.

A ChatGPT-like approach will not save loons. We simply cannot eliminate all threats. In fact, many factors that loon conservationists perceive as threats pose little or no hazard. The best example is human recreation. While lead sinkers are a danger to loon populations because of the many breeding adults they kill each year, loons are well-equipped to handle boaters. Loons tremolo, wail, or yodel when boats are too close to them or their chicks. They penguin dance, charge, and dive noisily at boats that creep close to their nests. Humans usually interpret these warnings correctly and back away in short order. Moreover, the low rates of mortality and nest abandonment attributable to boating activity indicate that loons tolerate human interactions well.**

How do we distinguish between relatively benign environmental factors, like boating, and those that truly endanger loon populations, like black flies, lead sinkers, and water clarity? Science. Only science will save loons. If the Minnesota loon population is declining and 50% of loon deaths result from lead poisoning, the folks in Saint Paul will take notice. If Wisconsin loons fledge 40% fewer offspring nowadays than in 1995 because of lower water clarity, that will make headlines in Milwaukee. And if the fledging rate across the Upper Midwest is 30% lower owing to black fly-induced nest abandonments, that might turn apathy concerning climate change into action.***

So if you are an unprincipled student being taught by an inattentive instructor, ChatGPT might earn you a “B” on your history paper. And if you cannot get the wording right in a letter to a client or colleague, ChatGPT might provide suggestions. But we loon conservationists should resist the uncritical, shotgun approach that ChatGPT takes to addressing questions. If we are going to preserve loon populations that we treasure, we must first collect data. And then, in our communications with the public, politicians, and the media, we must highlight the specific environmental hazards that science has shown to be dangerous to loons.

* The featured photo was taken a week ago by Linda Grenzer of an adult male from Lake Winter, Wisconsin that swallowed a lead sinker. Though the sinker was surgically removed by Raptor Education Group in Antigo, the male died two days later from the lead it had already absorbed.

** I might be biased by my work in Wisconsin and Minnesota in my conclusion about loons coping with boating activity. It is conceivable that boats do cause enough nesting failure and/or chick mortality in some regions to threaten loon populations. We do not have data to show such a pattern, however. If you know of such data, please let me know.

*** I made up these three numbers. We are still collecting data on loon mortality caused by lead sinkers. Only recently have we learned about the threats of black flies and loss of water clarity. We and our partners are recording many lead-poisoned loons these days. We will publish an estimate of lead’s impact within five years. Robust estimates of the impacts of black flies and water clarity on loon populations in Wisconsin (and possibly Minnesota) should be available by sometime in 2025.

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There is a certain sameness to each of our lake visits. At the boat landing, I don my PFD, slide my solo canoe gently into the water, place my circuit box in front of the seat, step gingerly into the center of the boat while grasping both gunwales, and urge my canoe away from the dock. Once clear of the landing, I scan the lake with binoculars to find the breeding pair. We maintain contact with the loons for exactly an hour, a period of time that — we have found — allows us to assess the birds’ breeding stage, find any nest or chicks, and get a snapshot of their daily lives.

And yet each visit is unique.

I had cause to reflect upon the uniqueness of lake visits this year. Since we had a strong and experienced field team in Wisconsin, I was free to focus on Minnesota in 2023. In late May, when I joined Eric Andrews to help covering our Minnesota lakes, I had a vivid recollection of Roosevelt, Sibley, Big Pine, and the Whitefish Chain from two previous years. But I could not recall whether I had been to Perry or Adney or both. I kept confusing Shaffer with Lynch, Buchite with Square and Sand. And I had not even visited scores of our Minnesota study lakes during daylight hours. This year, that changed.

Among my most vivid recollections from 2023 in Minnesota is Kego Lake, a shallow 120-hectare water body in the Fifty Lakes region. Kego is beautiful and quiet. Vast stretches of its shoreline are undeveloped. During my two visits there, I often caught myself thinking I was on a remote northern lake.

Kego appears a promising lake for loons. The lake contains two permanent islands. Each is far enough from the mainland that only a very reckless raccoon would dare to swim out to it in hopes of plundering a loons’ nest. While its depth limits the variety of fishes found in Kego, perch, crappie, and bluegill are present in good numbers.

When I first launched a canoe onto Kego on June 6th, I spotted a loon pair preening off of the eastern island. On a hunch, I paddled between the duo and the island. The male abruptly stopped preening and approached my canoe. Heeding this dead giveaway, I quickly located a nest with one egg on the adjacent shore of the island, took a hasty GPS point, and skedaddled so that the loons could incubate the egg if they wished.

I returned to Kego on July 17th. I tried to rein in my expectations for a hatch. After all, the pair had a poor track record. In 2021 and 2022 they had nested in this promising habitat and failed to raise a chick. Yet somehow, quite irrationally, I had hope for this year based on the male’s determination to protect his nest the month before. Initially, the pair was nowhere in sight. But when I paddled out to the nest island and brushed aside numerous leaves, sticks and other debris that had fallen onto the nest, I found the telltale scattering of small, angular eggshell fragments that signifies a successful hatch.

An innate worrier, I scanned the lake anxiously. “Where are they?” I muttered to myself. Moments later, my fear subsided. The pair and four-week-old chick were foraging intensively in the northeastern corner. So not only had a chick hatched; the chick had grown into a vigorous and enthusiastic diver.

I paddled cheerfully towards the loons to confirm that all three were healthy and estimate chick size for our records. As I drew near, the family began to linger on the surface between dives and eye me suspiciously. I backed off and smiled to see the male and female bracket their offspring between them protectively as they slowly led it off to the southeast and out of my path. Recalling the male’s assertive nest defense six weeks before, I concluded that this year’s pair was determined to leave their past failures behind. This year, it seemed, they would exploit the propitious breeding conditions on this lovely and distinctive lake and fledge a chick without fail.

Crude video of the Kego pair leading their chick slowly away from me after a foraging bout.

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Perched on the bow of a small motorboat in the middle of the night, I sweep a spotlight back and forth across the lake’s surface. My goal is simple. Find any small item resting on the dark water that catches the light. “Buoy”, Claudia proclaims in my ear as I freeze the spotlight on one such object that, at first blush, appears to be a loon. “No”, she barks a moment later, when I find a floating clump of vegetation. But shortly afterwards, the light falls upon something small, fuzzy, and brownish that becomes more and more loonlike as we approach it. I hand the spotlight backwards over my head to her, scooch as far forward as possible on my knees, and glance at the net to confirm it is untangled. Richard slows the boat and turns towards the loon family. “Adult!”, I whisper to Claudia — needlessly, because we had already agreed that we would first attempt to catch the parents. She trains the light on the larger of two adults whose physical features become dimly visible as we pull within fifty meters. On this occasion, luck is on our side; the male and female become alert as we draw near, but neither dives. We net the male without difficulty and, shortly afterwards, the female. The chick dives once after we fix him in the light. Seconds later, attracted by my loon calls, he wheels, swims towards the boat, and dives smoothly into the net that I place in his path. We quickly text Terri so that she can prepare the bands and datasheets on shore. Twenty two minutes later we have marked and weighed all three loons, transported them back to the capture site, and released them. Then it is on to the next lake.

One’s world narrows during loon capture. In the moment, all that matters is whether we netted this or that adult or chick we wished to band. Now that the sleep deprivation and tunnel vision of the capture period has subsided — and our nips and scrapes from loon bills have mostly healed — we can look back at our achievements over the season as a whole.

Between West Fox Lake in Minnesota, where our efforts began, and Oneida Lake in Wisconsin, where we wrapped up our season, we captured and banded 134 loons this year. Terri and Richard saved us in Minnesota with their expert boat-handling and organizational skills. Emily and Danny from the Wisconsin team were essential to our capture there. A huge thank you to all team members, who made 2023 a great year.

The research landscape differs starkly between the two study areas. In Minnesota, breeding pairs on Kego, Mitchell-East, Mitchell-West, Goodrich-Southeast, O’Brien, Clamshell, Kimble-West, Margaret, Big Trout-Far West — and dozens of other territories — got bands for the first time. The return or non-return of these adults in future years will allow us to refine our estimate of adult survival in the region and build the first-ever quantitative population model for the state. Thanks to our growing list of Minnesota partners and friends, who greased the skids for our work there with donations of funds, lodging, field work, lake access, advice, information about loons on their lakes — and moral support!

Having marked almost all adults in the Wisconsin Study Area decades ago, we now focus on marking chicks. Chick mass, we now know, provides a convenient assay of water clarity during the chick-rearing period. While we have already shown that increased black fly populations and falling water clarity have dealt the Wisconsin loon population a devastating one-two punch, there is more work to be done in the state. If we can pinpoint the exact environmental factor that reduces water clarity — our current research target — we might learn how to stem the population decline.

All of our research findings require loon capture. Although it is not foremost in my mind at those moments when I am kneeling in the bow of a small motorboat and inspecting fuzzy brown spots on the water, our work — our ability to learn about loon populations and what ails them — depends critically upon catching loons, weighing loons, and knowing who they are.

Thanks to Barbara Krimmer of South Two Lake in Wisconsin, who took this nice photo of the female (left), male (right) and two big chicks there.

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Something feels different in northern Wisconsin this summer. Loon chicks are doing far better than in years past — and there are far more of them. Historically, chicks weighing over 3000 grams comprise only 1.4% of all chicks we capture. And we had not captured a chick of this size since 2017. Yet during the past five nights, we caught four such monsters on three different lakes. Gone too are the emaciated chicks from small lakes whose prominent skeletons cast doubt on their survival prospects. Last night, for example, we caught two fat, healthy chicks on tiny East Twin Lake. Their high and similar masses told us that their parents had not been forced into the usual Sophie’s Choice of favoring the older chick over the younger in feedings. Finally, there are more two-chick broods this year. At last count, 26 of 53 pairs with chicks in the Wisconsin Study Area still had two chicks, not just one. The robustness and abundance of loon chicks this year makes 2023 look like 1995.*

Two years ago, I would have scratched my head to see a sudden bounty of healthy chicks on lakes in Oneida, Vilas, and Lincoln counties. I have grown used to the demoralizing downward trajectory of loon reproduction in the area: 80% singleton broods, striking size asymmetry of two-chick broods on small lakes, and high chick mortality. Two years ago, I would have offered a few hypotheses to explain loons’ strange reversal of fortune in 2023. But I would not have understood it. However, we have been able to pinpoint specific environmental factors that affect body condition and survival of loon chicks.

How can we explain the abundance of fat, sassy chicks that we see in Wisconsin in 2023? In a word, drought. We now understand that the ability of loon parents to feed their chicks depends critically upon short-term water clarity. That is, water that is clear during the period of chick-feeding allows parents to find food for their chicks; murky water hinders chick provisioning. Furthermore, we have recently learned that heavy rainfall reduces water clarity — probably because rain washes lawn fertilizer, pet waste, and other human-related matter into lakes that supports phytoplankton growth. The low rainfall in northern Wisconsin during June and July 2023 exposed the region to a greater hazard of fires, but it kept lakes clear. That was great news for loon chicks and their parents.**

I am thrilled about the throwback year loon chicks are having in 2023. Each night I am dazzled by the size and vigor of the chicks we are marking. But since it has taken a substantial drought to produce chicks as healthy as those we saw routinely in the 1990s, the thriving chicks of 2023 also remind me how far we have fallen.

*The featured photo shows the 2023 field techs in Wisconsin holding the three strapping chicks from Kawaguesaga-North.

**Folks in Minnesota must be thinking, “Hey, we are in a drought too! What about our water clarity….what about our loon chicks?”. Our capture effort in the Minnesota Study Area occurred in mid-July. We marked dozens of new adults, but most chicks were small at that time. So we were not able to get good enough measures of older chicks in Minnesota to learn whether the drought gave loon parents a boost there, as in Wisconsin, by keeping lake water clear. However, we strongly suspect that the positive “drought effect” for chick feeding spanned the two states.

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The two-year olds have done it again. At an age when most loons are loafing, feeding, staying out of trouble, and just trying to survive, a second two-year-old has shown territorial pretensions. This time, the loon is a female. This time, the territory is in our Minnesota Study Area.

The discovery occurred three days ago on Pig Lake. Although I always smile at its undignified name, I was a bit sad to visit Pig, because neither pair member from 2022 had returned this spring. This fact reminded me of the generally poor return rate in Crow Wing County and my growing concern for loons in Minnesota. So as I gazed through binoculars at the whitecaps on Pig, I braced myself for what more bad news the lake might have to offer.

But among the four loon heads bobbing about in the surf, I was thrilled to spot a banded loon. This bird was one of a pair that dived in close synchrony off of Black Pine Resort. “One of the missing pair members is back!”, I whispered to myself, hopefully. Further observation dispelled that notion. The loon’s right leg showed two colored leg bands. Since all loons banded as adults get a metal band on the right leg, two plastic bands on the right leg meant that I was not watching one of the missing pair members, but instead observing an “ABJ” (adult banded as juvenile). That is, we had banded this loon as a chick.

Two possibilities leapt to mind. This bird might have been a one-in-a-million, 200-mile disperser of undetermined age from the Wisconsin Study Area, where we have been banding adult loons and chicks since time immemorial. Almost equally unlikely, the ABJ might have been one of our first crop of Minnesota chicks banded in 2021. The plot thickened as I compared the size of the ABJ and its mate. The banded bird was clearly smaller. I was looking at a rare female ABJ!*

My efforts to nail the ABJ’s color bands from my solo canoe were not immediately rewarded. I loosely followed the foraging pair, bobbing and spinning about comically amidst the churning waves and boat wakes. Eventually a moment came — forty minutes into my chaotic paddle — when the ABJ and I were carried to the crests of adjacent waves and the bird raised its legs clear of the water. I confirmed that the bird was blue over auric red on the right and red over silver on the left. “B/Ar,R/S”, my notes revealed, was marked as a chick on Ossawinnamakee – Muskie Bay territory on 18 July 2021. So this was indeed a two-year-old female hatched a short distance from Pig.

Like the two-year-old male who is trying to settle on his natal lake in Wisconsin (pictured above in Linda Grenzer’s photo), B/Ar,R/S is special in two ways. She is not only the first chick we banded in Minnesota and have now reobserved as an adult. She is also less than half the age of the previous youngest female ever observed to settle (even for a day) on a territory. (That female was a Wisconsin five-year-old.) Since females settle at older ages than males, her pairing up is even more surprising than settlement of the two-year-old male in Wisconsin in the photo.

What are we to make of this astonishingly early territorial behavior by separate individuals in Wisconsin and Minnesota this year? Nothing at the moment, I think. Two rare events do not constitute a pattern. But those who follow the blog closely might recall that a decline in the population of floaters — mostly young adults not yet settled on territories — is one of the hallmarks of the current downward turn in the Wisconsin population. If we continue to see two- and three-year olds compete for territories in ways they did not 15 years ago, we will have to regard it as another indication of a limited pool of nonbreeders in Minnesota and Wisconsin** — and, hence, further evidence of a broad decline in the Upper Midwest loon population.

*most loons banded as chicks return at three or four years of age. Among those few that return at age two, very few are female. Indeed, about 3/4 of all ABJs we see are males, because males do not disperse far from their natal lakes to breed.

**The logic is simple here. If there are few young adult floaters (usually 4-, 5- and 6-year olds) in a population competing for territories, then even very young floaters (2- and 3-year olds) might be able to acquire one, despite their generally lower competitive ability and aggressiveness.

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On the Loon Project, we are all out to band loons in Minnesota. This effort borders on obsession. Since adult loons must produce chicks to be easily catchable, our marking initiative depends upon finding pairs with chicks. “Have you seen any loon nests on your lake?” is a refrain Eric Andrews and I uttered to many residents of lakes in Crow Wing and Cass Counties back in May and June. “Have you seen any chicks?”, I have begun to ask in recent days, now that I am on my second tour through the Minnesota Study Area. This question is on my lips so often that I now smile inwardly each time I ask it. I hope that I do not sound desperate.

People have been happy to answer our loon-related questions. Driven by love of the state bird, scores of Minnesotans have shared their observations of loons, nests, and chicks, given us permission to launch canoes from their property, and even permitted us to post their photos of loons to spruce up our blog and Instagram posts. (Sheila Farrell Johnston’s cool photo, above, of a territorial battle on Upper Gull Lake this spring is a case in point.) Minnesotans, it seems, are as concerned about loons as we are and wish to help us enhance the current low-resolution picture of the state loon population with a robust, scientific analysis. The outpouring of support we have received this summer has ended any lingering uncertainty we had about continuing our research in the region. *

A growing demographic disparity lends urgency to our efforts in Minnesota. You see, accumulation of data from the Minnesota Study Population — and comparison with corresponding data from Wisconsin — has revealed that loons are returning to their territories at a lower rate in Minnesota than in Wisconsin. That’s right. In Wisconsin, where we already know the population is in some trouble, adult loons are returning to their territories at a higher rate than in Minnesota.

The numbers speak for themselves. In 2023, 63 of 74 Wisconsin territorial females (85%) returned to their 2022 territories, while 69 of 79 Wisconsin males came back (87%). Those numbers are typical for Wisconsin and for New England loon populations as well. In contrast, only 81% of Minnesota females (34 of 42) and 82% of Minnesota males (37 of 45) returned in May 2023 to the territories they owned in 2022. Now, these are not massive samples. So you might be excused for dismissing these numbers as sampling error from which no conclusion can be drawn. But this is the third independent analysis that has shown a higher rate of return in Wisconsin. We saw the same story in the data from last year and from Kevin Kenow’s marked adults from 2015-2017. So the time for hemming and hawing is over. We can no longer escape the fact that loons in Crow Wing County are returning to their territories less often than loons in Oneida County, Wisconsin.

Before you hurl yourself off of your dock, let me add some perspective. The lower return rate in Minnesota does not necessarily indicate lower survival there. Why not? Because a loon’s ability to return to its previous territory depends not only upon its being alive, but also upon its ability to defend its territory from challengers. Minnesota loons might be surviving just as well as — or even better than — Wisconsin loons. If so, however, they are being evicted from their territories at an astonishingly high rate.

Paradoxically, a high rate of eviction in Minnesota, if it is occurring, could be good news. A high eviction rate might indicate that Crow Wing County is overflowing with young 4-, 5-, and 6-year old adults looking to challenge owners for territories. If so, frequent eviction reflects high breeding success of loons in the County (4 to 6 years ago), because it is Crow Wing County loon pairs (for the most part) that have placed all of these young whippersnappers into circulation.

Ok, I admit it. I am putting lipstick on a pig. I do not truly believe that our Minnesota loons are kicking each other off of territories often enough to account for the low return rate we have found there. I do not know how to account for the pattern. But I am yet not unduly concerned about our Minnesota Study Population. Adult survival, even if lower in Minnesota, is only one piece of the puzzle. Still, the news is pushing me to be even more inquisitive of Minnesota lake residents. Someone listening closely late this afternoon might have heard my favorite question echo across the gently scalloped surface of Duck Lake: “Have you seen any loon chicks this year?”

*Mind you, we are still enthusiastically following our long-term study population in northern Wisconsin. Wisconsin loons continue to yield exciting insights about age-related behavior patterns and impacts of water clarity on the health and survival of loon chicks.

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History is afoot on Muskellunge Lake. A two-year-old male is making a play for a high-quality territory….which is pretty shocking. 

Let me put this into perspective. Only about a quarter of all two-year-old loons even bother to return to the nesting grounds. The vast majority of all loons of this young age from eastern and midwestern breeding populations are cooling their heels in the Atlantic right now. Some are off of the Carolinas; some New Brunswick. The bulk of all two-year-olds play the long game: they retain the drab grey-brown winter plumage throughout their first two years, stay healthy on a saltwater diet, and postpone any thought of breeding until they acquire sufficient body mass to compete for a territory in their fourth or fifth year.

We have never observed a two-year-old adult male or female settle on a territory. Indeed, we have only once observed a loon as young as three claim a territory — and that was very late in the season and in a vacant space without competitors. (His mate, sad to say, was his mother.)

As territorial intruders, two- and three-year-old adults are nervous Nellies. They sit low in the water while circling with territorial pairs and are deathly afraid of underwater attack. They peer (look under water) and panic dive obsessively. When anxiety overwhelms them, they freak out and flee across the water tremoloing. In short, two- and three-year-olds do not appear emotionally equipped for territory ownership.

But “Junior”– as Linda calls the two-year-old that has settled on Muskellunge — threw out the book on reproductive maturation. When the 12-year-old male that took over on Muskellunge this year became injured in early June after a failed nesting attempt, Junior took possession of the lake and began defending it vociferously with territorial yodels (as you can see in Linda’s photo, above).

For a time, it seemed that Junior would ease into lake ownership without a battle. Yet news that Muskellunge Lake was up for grabs spread fast in the neighborhood, and the last two weeks have seen multiple local males vie for control. One of these males, from nearby Deer Lake, has tried to claim Muskellunge before and is renewing his bid. A second male, this a ten-year-old reared on neighboring Clear Lake, seemed settled on Harrison Flowage last year but is apparently looking to upgrade. 

Junior’s age is not all that makes his story unusual. He is also the only young adult (out of 211 observed so far) that we have ever observed to compete for ownership of his own natal territory. In this he is fortunate; the current breeding female on the lake, who will probably pair with the victorious male, is not Junior’s mother, but instead a female that took possession of Muskellunge last year.

According to Linda’s reports, Muskellunge remains in an uproar. One day Junior is in control and paired with the resident female (or the Bridge Lake female, whose mate did not return this spring). The next day the Deer male has taken ownership and patrols the lake, searching for Junior, who evades him. 

Linda and I are trying to celebrate the oddity of a two-year-old territory owner and not overthink it. But it is difficult to sit back and pretend to be neutral. After all, Junior got his name because he is the son of Clune, the beloved male who settled on Muskellunge in 2009, cranked out 14 chicks during 14 years of territory ownership, and never uttered a discouraging word for canoe nor kayak.

And it is hard not to wonder how a loon as young as Junior even got a shot at such a good territory. Is his territorial gambit an anomaly — a one-time peculiarity that you are bound to observe once if you study a loon population for 31 years? Or must we interpret his premature, longshot bid for territory ownership as yet another indication of the depleted ranks of young nonterritorial loons that epitomize population decline in the region?