on

A few years ago, a team from Canada learned about the declines in loon populations that have been found by researchers in Ontario and Quebec and by us in Wisconsin and decided that it was time for a documentary. It took the company a few years to make the film available in the U.S., but now it is streaming on Peacock. The title is “Loons: A Cry from the Mist”.

One never knows how these pieces will turn out. The producer tells you that they want to interview you on such and such a date against this background and have you talk about this, that, and the other thing. Of course, you try to steer the interview towards topics that you deem most important. In the end, the producer and editor (I think) stitch together some of your comments and some comments of others to create the best possible story. You can only sigh to learn that your best quips ended up on the cutting room floor.

I cringed at a few aspects of the film. Like many others before them, these filmmakers could not resist the patently false idea that loons are ancient. Mercury, which has been studied for decades yet still has not been shown to have more than weak negative impacts on loons, is portrayed as a likely cause of the decline. The age at which loon chicks reach independence is stated incorrectly. And, of course, I wish I had worn a nicer shirt!

On the other hand, I was proud of how well the 2022 Wisconsin Team handled loon capture. Because of scheduling, filming could only occur on our very first night of capture. Yet Molly, Chris, Sarah, and Claudia shrugged off my nervousness and looked like seasoned professionals. The crew got some dazzling footage from Canada and our Wisconsin Study Area. Their profile of Linda Grenzer and her loon pair, Clune and Honey, is sweet and uplifting. I did not sound like a complete idiot during my bits. Most important, I was able to highlight the high rate of young adult mortality that we are seeing in Wisconsin and the need to understand that recent pattern.*

In short, Yap Films produced colorful, entertaining, and largely accurate loon documentary describing the concerns that conservation scientists have about the species. If you have 50 minutes free, it is worth a look!

*Of course, we now know that the decline results in large part because of poor feeding conditions early in life, which ruin a loon’s chances at a long, fruitful life. Too bad the film was not made a few years later!

on

If you have been following my blog, you are aware of a worrisome set of circumstances. Survival of Wisconsin adults is as high now as ever, but breeding success has fallen sharply. And the negative silver spoon effect I detected this fall compounds the reproductive downturn. Underfed chicks are unlikely to survive to adulthood. Those that do survive are unlikely to claim a territory and raise chicks themselves. In other words, Wisconsin breeders produce fewer and poorer quality young than before, which contributes to population decline.

And matters are worse in Minnesota. Our data from northcentral Minnesota show: 1) consistently lower adult survival than in Wisconsin, 2) breeding success on a par with Wisconsin, and 3) a more severe silver spoon effect. That’s right, adult loons in Crow Wing and Cass counties experience lower overwinter survival than their Wisconsin counterparts and have been rearing young of poorer quality in recent years. Here is a figure showing the latter pattern.

As you can see, Wisconsin breeders have actually bounced back to raise healthier young in the past few seasons! This is excellent news, and we hope the pattern persists. But Minnesota breeders have gone the opposite direction. Why is this a concern? As the figure below shows, the probability that a loon reaches adulthood depends upon its mass as a chick.

Thirty two years’ of data in Wisconsin have shown that loon chicks with a mass/age value above 80 have about a 50/50 chance of returning to the study area as adults. Roughly 42% of those with mass/age values of 70 to 80 come back as adults. Chicks in mass/age classes of 60 to 70, 50 to 60, 40 to 50, and below 40 return at rates of 36%, 28%, 18%, and 14%, respectively. Now look at the mass/age data from Minnesota for the past two years:

The future looks bright for the Big Trout-West chick we banded in 2023, the larger Cross-South of Happy Bay chick from 2023, and the Fawn-E chick from this past summer. Things look fairly rosy for both Island-Channel chicks from last year, the Goodrich-SE chick from 2023, the Kimball-West chick from 2023, last year’s Little Star/Star chick, two of three Lower Hay chicks from 2024, the alpha Margaret-North chick from 2024, the chick on North Roosevelt, the Lower Cullen-SW chick from 2024, the larger of two 2024 chicks from Cross-Arrowhead, this year’s Roy-South chick, the alpha chick from Ossie-Island, and the Little Pelican-South chick from 2023. The remaining 51 Minnesota chicks were below average size (56 grams/day). Hence, 75% of 2023 and 2024 chicks from Crow Wing and Cass counties stand very little chance of reaching adulthood. Even if they beat the odds and do so, they are unlikely to produce a single chick.

In light of these patterns, I am getting a sinking feeling about Minnesota loons. Of course, the worrisome data come from only the past two years and one part of the state. Perhaps these years were atypical, and Minnesota loons will bounce back this summer. I hope so!

The featured photo shows the female from Rush Lake-Channel in 2024 as she alertly approaches an intruder. Photo by Isaac Pavalon.

on

The Silver Spoon Effect occurs when individual animals that experience favorable circumstances early in life — like abundant food — enjoy long lives and produce many offspring when they reach adulthood. In essence, growing up well-fed places a young animal on a track to become successful as an adult.

The Silver Spoon Effect is strong in loons of the Upper Midwest. How do I know this? I have just done a massive analysis of factors associated with return to the breeding grounds among loons banded as chicks. I learned that chick mass (adjusted for age) is the single strongest predictor of both survival to breeding age and breeding success. That’s right: a loon’s mass as a chick accurately predicts how long it will live and how many young it will raise.

This does not mean that a loon chick that grows up without adequate food is guaranteed to die young and raise no chicks. Nor does it mean that a fat, healthy chick is certain to survive to adulthood and have many offspring. After all, it is a statistical pattern. But body mass in chicks is a very strong predictor of lifelong success. The graph below shows the effect.

Loons that did not survive to breeding age tended to be those with low mass as chicks (top row). Loons that survived to return to the breeding ground but never raised young (middle row) tended to be of intermediate mass as chicks. Loons that became successful breeders were mainly those that had been heavy as chicks.

It is hard to know how to feel about the Silver Spoon Effect. On the one hand, it seems cruel. One would love to think that a loon chick could overcome a rough start and turn its life around. But such a turnabout rarely happens. A juvenile that struggles to get enough food in its first month might make its first migratory flight to Florida. However our data show that such a loon has very low odds of surviving beyond its first few years.

On the other hand, loons reared with a silver spoon become the reproductive pillars on which the population’s persistence depends. Take the Pickerel-West male pictured in Hayden Walkush’s photo above. This male — “yellow over white-blue, auric red over silver” (Y/Wb,S/Ar in the table below) — was 8% heavier than average when we captured him on Tom Doyle Lake on August 3rd, 2013 with his parents and younger sister. He was then five weeks old. The momentum that his parents built for him gave him good odds of surviving to adulthood, settling on a productive territory, and rearing young himself. Indeed, he has already fledged six chicks on Pickerel with two different females despite being only eleven years old.

“Yellow over white-blue” is not exceptional. In the table below, you can see the list of all of our recent Wisconsin breeders that were marked as chicks. (Most are males because of the much shorter range of natal dispersal by males.) Pay particular attention to the right-hand column (“% above avg”). A “0” in this column indicates that this loon was of average mass for its age as a chick. If this were a random set of loons, the red numbers would all fall around zero; some a bit negative, some a bit positive. In fact, the table looks like something from Lake Wobegon: almost all territorial breeders in our study area were well above average mass at the chick stage. Sixty-five percent were absolute whoppers — 20% or more above average mass. This is a good illustration of the strength of the Silver Spoon Effect. (The pink-shaded cells show the few current breeders that were of below-average mass as chicks.)

Breeding lake, natal lake, band combination, sex, Chick Mass Index, and % difference from population average for current breeders in the Wisconsin Study Area.

The table shows something clearly. Territory settlers are the cream of the crop. Yes, there are a few overachievers — Harrison Flowage, Manson, Nose, Sherry, Silverbass and Soo. But their small number speaks to the strength of the pattern.

Leaving aside the fascinating and often brutal nature of silver spoons, let’s look at the implications of the pattern for loon conservation in the Upper Midwest. If you recall, the young adult “die-off” that we have found there is the most troubling aspect of the current population decline. Put simply, we are losing the vast majority of all young adults between the time they leave the breeding grounds as juveniles and return to it as adults 2 to 4 years later. This mortality must occur at some stage(s) of the life history of young loons — like migration or winter — that we have not studied well.

Average +/- standard deviation for Chick Mass Index from 1998 to 2020.

Here is the critical point. I have been suggesting that a decline in habitat quality along the migration route or on the wintering ground in Florida might be responsible for the die-off of young adults. But look at the graph above. Chick Mass Index has slid downwards steadily during the past quarter century. This means that the number of loons “fit” enough to survive to adulthood, claim territories, and rear chicks has also declined steadily. So loons are likely not dying because of environmental degradation on the migratory path or in Florida. Rather, loons themselves are of poorer quality than they were 15-20 years ago owing to limited food they received as chicks and can no longer survive the same challenges as well they used to.

Thus, the Silver Spoon Effect forces us to confront an uncomfortable reality: factors on the breeding grounds — during the chick-rearing period — are almost certainly contributing strongly to population decline. We cannot blame Florida.

But the silver spoon has a silver lining. Why? If we can improve lake conditions in Wisconsin and Minnesota so that loon parents can feed their chicks amply each July and August, we can help them raise fit chicks. And those fit chicks will grow up to become robust, successful breeders and strengthen the population.

So the answer, after all, lies in the lakes of the Upper Midwest. And my current push to discover the exact cause of water clarity decline in Minnesota and Wisconsin lakes suddenly takes on even greater importance.

$20,000 Match from a Wisconsin Foundation

If you have already donated to support our work, thank you! If have not yet done so recently, this would be a great time. Earlier this week we learned that a northern Wisconsin foundation will match every dollar raised from other sources up to $20,000. So every dollar that folks are able to donate will add $2 to our 2025 research fund.

DONATE HERE

We would dearly love to take advantage of this opportunity and field a strong research team next year. Thanks in advance, if you can help!

on

This seems a dark time for loons in the Upper Midwest.

Wisconsin breeding pairs fledge 26% fewer chicks now than they did 25 years ago. Our more limited data from Minnesota indicate low breeding success there as well. (A long-term study by Minnesota DNR confirms that chick production is decreasing in the state.) The decline in breeding success across the Upper Midwest concerns me. Do enough chicks still reach adulthood so that they can sustain the population of breeders?

But, as I have discussed in previous posts, loss of chicks while under their parents’ care is less of an issue than the escalating die-off of young adult loons after they leave the breeding grounds. Survival in this later stage of the life history is down over 80%. Of 99 chicks that we banded in 1998, 1999, and 2000, we had resighted 38 (38%) as adults by 2004. In contrast, we have reobserved as adults only 9 of 155 chicks (6%) banded between 2018 and 2020.*

Of course, these young adult returnees are troublemakers. They loaf on undefended parts of large lakes or on vacant small lakes. They intrude into breeding territories. Their visits force pair members to confront them physically and steer them clear of chicks. If the pair’s hints are not sufficient to drive the youngsters off, they are attacked. Naturally, the more of these 2- to 6-year-olds there are in the study area, the greater the chance that one of them evicts a member of the pair.

But these young loons are also the future. From their ranks come replacements for breeders that die each year. So young adults — warts and all — are essential to population stability.

The huge drop in the young adult population has turned our annual spring census into a stressful experience. In early May our Wisconsin and Minnesota teams race from territory to territory to see which of our marked breeders have returned and which territories from previous years are still occupied. Each year I fear that breeding lakes will be lost because the dwindling young adult population will be unable to fill breeding vacancies.

In truth, we have lost several of our traditional territories in Wisconsin during the past few years. We did not find breeding pairs on Bridge, East Horsehead, Hildebrand, Miller, Oneida-East, Pickerel-North, Tom Doyle, Swamp, or Muskellunge (Lincoln Co.) in 2024. We seem to have lost one of our breeding pairs on Bertha Lake and another on Butterfield Lake in the Minnesota Study Area as well, although our data do not extend as far back there. Still, there has not been a wholesale loss of territorial pairs in the Upper Midwest, which one might have expected from the high mortality of young adults. So while we have far fewer young nonbreeders milling around, the decline in the territorial loon population is, as yet, small.

Thus, the loon population might be more resilient than we had feared. We have long known that the majority of young loons that return to the breeding grounds never settle on a territory. Perhaps the die-off of young adults merely reduces their number to those few that would normally claim territories anyway. It is a hopeful thought!

Meanwhile, my work continues in both states. I am connecting with water quality specialists in Wisconsin and Minnesota in hopes of learning why we are losing water clarity in July, which harms loon chicks. And I am searching feverishly — both on the breeding grounds and in Florida, where most of our birds winter — for the cause of the high mortality in young adults. These are not quixotic quests. I feel that people who love loons in the Upper Midwest will step up and help them if we can pinpoint the factors that endanger their population.

If you would like to support my efforts to conserve loons in Wisconsin and Minnesota, please consider a donation to our 2025 field effort. We squeeze all we can out of every dollar we receive.

* People sometimes ask me, ”Could these missing loons have simply gone somewhere else? Have they gone to Canada?” It is a reasonable question. Ecologists have marked and tracked movements of thousands of bird species as well as many other vertebrates. With the exception of nomadic species, though, territorial animals like loons stick to a rigid set of guidelines with respect to settlement. If it is still alive, a loon will return to the near vicinity of its natal lake as a young adult to look for a breeding spot. (This is especially true of males.)

The featured photo is by Hayden Walkush of the territorial female on Two Sisters-East. This photo is among the 1906 taken by the team this year as part of our study of whether or not loons can be distinguished using artificial intelligence.

on

Almost four years ago, I wrote a blog post about the importance of Florida’s Gulf Coast as a wintering area for loons breeding in the Upper Midwest. I pointed out that 75% of loons breeding in Wisconsin and Minnesota winter along the Gulf Coast of Florida from Pensacola to Fort Myers. And I suggested that conditions in Florida were likely to have substantial impact on the loons we see on our lakes in the north.

My thoughts have returned to Florida of late. Why? Because recent findings suggest that the answer to our greatest riddle might be found there.

Followers of the blog may recall that the single most worrisome pattern related to the Upper Midwest loon decline is the mysterious disappearance of juvenile loons before they reach adulthood. In Wisconsin, the survival rate of juveniles to adulthood plummeted from above 50% to less than 20% between 1993 and 2016, as the graph from our statistical test shows.

The problem has gotten worse since 2016. Only 13 of 209 chicks (6.2%) banded in Wisconsin between 2017 and 2020 have returned as adults. That is a ghastly statistic.

What might be the cause of this massive die-off of young loons? We have good data from the breeding grounds. If juvenile mortality were high during this interval, we would have detected it. Death during migration is another possibility, of course. We do not have good data from that period. But it seems implausible that the varied array of aquatic habitats used by young loons along the migration route have suddenly become a death trap for them.

So it was with increased urgency that I turned my gaze to Florida two weeks ago with our juvenile return data in hand. My hope was to take a second, more thorough look at the likelihood of spotting loons two to four years after we marked them as chicks. I had taken a preliminary glance at this pattern 12 years ago. This time I had: 1) twice as much data, and 2) measurements of physical and biological patterns from ocean water along the Florida Gulf Coast that might help explain the decline. Among physical and biological ocean attributes that I could examine this time were water clarity, temperature, pH, salinity, and concentrations of Chlorophyll A, dissolved oxygen, nitrogen, and phosphorous.

What do the data show? After accounting for observation intensity 2-4 years after banding (which has varied during the study) and location of lake where the chick was banded (because juveniles from central lakes are spotted more often), three variables strongly predict the probability of resighting of a color-marked juvenile loon. In order of decreasing importance, they are:

  • Year — The likelihood of spotting a banded chick as an adult has decreased by an average of 8% from one year’s “crop” to the next. This is the alarming pattern that I seek to understand.
  • Body condition at banding — Chicks that are heavy for their age when banded are much more likely to be resighted as adults.
  • Chlorophyll A level in Tampa Bay in December of the first year — Chicks are much less likely to return if Chlorophyll A levels in Tampa Bay were high in December of their first year (see graph below).

Wait! Does this last finding make sense? First, it is vital to understand that Chlorophyll A is a measure of aquatic phytoplankton — the microscopic algae that can make water appear green to us. A very high concentration of Chlorophyll A can indicate an “algal bloom”, which reduces water clarity and can lead to loss of oxygen and release of toxins. Second, it is important to understand that the negative impact of Chlorophyll A on loons occurs only in December of a loon’s first winter. Return rate of juveniles is not associated with Chlorophyll A levels the month before (November) nor the month after (January). Third, we must be familiar the the migration schedule of juveniles. Juveniles reared in Wisconsin and Minnesota typically reach their Florida winter quarters in late November. Stitching all of this together, the negative impact of Chlorophyll A in December on return rate to Wisconsin suggests that many young loons perish in their very first month on the wintering grounds in Florida if algal levels are high at that time. We would expect these neophytes to be at risk during this period, because they must suddenly find new aquatic prey in wholly unfamiliar habitat. High algal levels add another layer of difficulty to foraging, likely reducing the abundance of prey as well as a loon’s ability to find them.

Of course, this is a hugely important finding. This is the first evidence — to my knowledge — where an occurrence in winter affects a demographic pattern detected on the breeding ground. The effect, moreover, is strong. And the pattern is evident despite the fact that Chlorophyll A data represent only one small part of the winter range (Tampa) that is as far as 350 miles from where some Wisconsin loons spend the winter. We can reasonably surmise that the pattern would be far stronger if we had complete data from all along Florida’s Gulf Coast and could match locations of wintering loons up with Chlorophyll A data from their exact location.

Unfortunately, this striking finding cannot explain the steep decline in juvenile survival rate over the past quarter century. Why not? First, Chlorophyll A levels have remained roughly stable in Florida — maybe even falling slightly — across the two decades or so when juvenile survival has been getting steadily worse. Second, the statistical decline in annual return rate among young adults remains strong even after we have accounted for the effect of Chlorophyll A.

In short, many of our first-year loons do appear to die in Florida, shortly after arriving there. But we are still utterly in the dark with regard to the continuing yearly decline in young adult survival. Young adult loons are future breeders — essential to the stability of the Upper Midwest loon population. It is urgent to learn what is killing them. I will keep looking.

The featured map is from Google Earth. It shows lines drawn between where a loon was banded in summer and where it was recovered or spotted during winter months. Green end points indicate Wisconsin breeders and red indicate Minnesota birds.

on

I thrive on routine and familiarity. When others gush about peculiar foods they ate as they slept in uncomfortable beds of strange hotels in foreign lands, I cringe. Yes, I laughed at Macon Leary’s decision, in “Accidental Tourist”, to eat at Burger King in Paris so that he would not shock his taste buds with new flavors. I knew his behavior was absurd. But my amusement was tempered by a harsh reality. I am Macon Leary.

Despite my disinclination to travel, I have to admit that visiting a new place can be curiously stimulating. In a new location, one’s brain is attuned to every novel detail — from the peculiar vegetation, scents, weather, road signs, and dwellings to the attire and speech patterns of the local humans and how they treat you. So it was two weeks ago when I visited lakes along the Gunflint Trail in Minnesota’s Arrowhead region.

The glacial lakes in this eastern gateway to the Boundary Waters are unusual. Most are long, slender, rather clear, and lie in an east-to-west orientation. The loons along the Gunflint Trail encounter many canoes and few motorboats. Observing this pristine habitat set me thinking about Upper Midwest loons in general. Could the factors that cause harm to loons in northern Wisconsin and north-central Minnesota — most of them related to humans — possibly reach them in this remote region?

Newly attuned to the contrast between lakes in regions of high and low human impacts, I sat down to take another look at loons and water clarity. I first looked to see whether masses of loon chicks from my Minnesota Study area (Crow Wing and Cass counties)* depend strongly upon water clarity, as we have recently found in Wisconsin. Regular readers of the blog will recall that the strong dependence of loon chick mass on water clarity is the hallmark of the recent population decline in Wisconsin.

Just as in Wisconsin, chick mass is dependent upon water clarity in north-central Minnesota.**

In Crow Wing County, Minnesota, chick mass increases with increasing water clarity. (Clarity calculated from satellite data and direct measurements available via the Minnesota LakeBrowser.)

Next, I examined climatic factors that affect water clarity. Is recent rainfall a strong determinant of water clarity in north-central Minnesota, as we have shown in Wisconsin? Yes it is.** As I have said many times before, rainfall appears to wash something into lakes that harms clarity.

Rainfall in loon lakes in Crow Wing County, Minnesota during the past 60 days causes water clarity to decline. (Clarity calculated from satellite data available via the Minnesota LakeBrowser.)

So loon chick survival is highly dependent upon water clarity across the Upper Midwest. And water clarity declines after rainfall across this region as well. These findings hold for two study areas 200 miles apart comprising lakes with extensive shoreline development and human recreational activity.

What about remote regions like the Gunflint Trail? We have no loon data from this region, so we can only infer loon chick condition on the basis of water clarity. Fortunately satellites pass over these lakes just as they do the lakes of northern Wisconsin and north-central Minnesota. Therefore we have just as crisp and complete a picture of water clarity along the Gunflint Trail as we do anywhere else.

First, a hypothesis. I have said countless times that fertilizer linked to lakeside lawns is a prime suspect for the “rainfall effect”. That is, water clarity probably declines after rainfall because of fertilizer and other matter from lawns that washes into lakes and triggers phytoplankton growth. This is just a hypothesis. I could be wrong. But the comparison of Crow Wing County lakes to Gunflint lakes permits a test of the hypothesis. A lack of a rainfall effect along the Gunflint Trail — that is, no negative impact of recent rainfall on water clarity — would support the hypothesis.

Rainfall in the Minnesota Study Area (Crow Wing County) is associated with a decrease in water clarity. In contrast, recent rainfall is linked to an increase in clarity among lakes along the Gunflint Trail.

As the above graph clearly shows, rainfall does not negatively affect water clarity among lakes along the Gunflint Trail. In fact, recent rainfall in the region is associated with a slight increase in water clarity. This finding is crucial. It strongly suggests that human development and/or activity is causing the rainfall-associated decline in water clarity in Upper Midwest lakes.*** This means that we can begin to narrow the scope of our investigation into clarity as a cause of chick mortality.

Every scientific investigation exposes at least one puzzle. Here it is. If water clarity in the Gunflint region is not negatively impacted by humans, we would expect high loon breeding success there. Yet long-term data from nearby portions of Cook and Lake counties (monitored by the Minnesota Loon Monitoring Program) show a steady decline in both adult and juvenile populations. ****

I have said, “It is such a relief to be home” so many times after returning from my summer field work that my wife now only smiles faintly to hear it. I love the lakes and loons of the Upper Midwest but remain the same unadventurous homebody now as before. Still, it is gratifying that my recent plunge into unfamiliar terrain led to new insights about loon conservation. Maybe I should stray from the beaten path more often.

* Thanks to Sheila Johnston for the featured photo. Sheila snapped a picture three days ago of the grown-up chick and it heavily-molting male parent on Bass Lake near Nisswa, Minnesota.

** These are “statistically significant” patterns. That is, they exceed the threshold for results to show a clear non-random effect.

*** Obviously, there are other possibilities, which we must examine.

**** We are getting into the weeds here. But — as Phyllis Sherman has reminded me — the Cook/Lake index area surveyed for the MLMP is not as remote as the Gunflint Trail area. Inspired by Phyllis’ comment, I took a look at water clarity within the Cook/Lake Index area lake specifically. They show a very weak rainfall effect on water clarity. So the puzzle persists. Loons are struggling to reproduce on remote lakes whose clarity is largely unaffected by human activity. Black flies, I understand, are a severe problem in the area. It is possible that black flies alone — or black flies together with other ecological factors yet unknown — account for the local population decline.

on

Life is a roller coaster when you pin your hopes to the breeding efforts of a single loon pair. If the male arrives in late April and the female does not show until early May, you fret. If the pair places their nest on the mainland rather than an island, you grit your teeth and prepare for four long uneasy weeks. If black flies hound the male and female on the nest, you curse the flies. And if two chicks hatch after the long ordeal of incubation, you weep sweet tears of joy.

During the decades she has spent pulling for the loons on Deer Lake in Wisconsin, Shirley Lamer has experienced plenty of ups and downs. Deer Lake had three straight years of chicks from 2003 to 2005*, but historically chicks have been more the exception than the rule. In fact, chicks have only fledged from Deer in three years since 2005.

Nesting habitat is part of the problem. It is not abundant on the 150-acre lake. Small marshy coves at the north end are tempting for a nest, but they offer no opportunity for an off-shore site. A permanent island halfway down the west side is, in fact, the most obvious spot. But even there danger lurks. The water between the island and the shore is shallow. Predators apparently reach the island easily when the lake level falls.

This year, all of Deer Lake’s past breeding woes are forgotten. On about June 9th, Sharon and Lonn** (named for Shirley’s parents-in-law) hatched two healthy loon chicks. Week after week Shirley followed the chicks’ development from fuzz ball to adult size. She giddily posted photos and videos of the loon family on Facebook when she encountered them in her kayak or they foraged near her dock. One of her chicks, which we banded in early July, stayed on the lake until the first week of September. The other remained on Deer until mid-September before flying off to feed elsewhere.***

But Deer’s two chicks were not the only cause for excitement on the lake this year. Two juveniles from nearby lakes landed in Deer. Knowing that we marked most of the chicks in the neighborhood, Shirley leapt into her kayak when she spotted these young visitors. Her efforts have paid off.

On September 11, Shirley found that one of two juvies banded on Crystal Lake had landed in Deer to feed. The Crystal juvie foraged loosely with the remaining Deer juvenile and Lonn, the Deer male. Four days later, Shirley identified the Jersey City Flowage chick as a second visitor. While the JCF juvie has gotten no food from Lonn — despite efforts at calling and following him — the juvie apparently found the fishing productive. He remained on Deer on September 16th also.

You might have noticed that I called the JCF juvie “he”. The JCF juvie is clearly a male. How do we know this? Because — as you can see from Shirley’s video below — he

Jersey City Flowage juvenile emits a truncated yodel while visiting on Deer Lake, Wisconsin on September 15. Video by Shirley Lamer.


yodeled during his visit. This is not the first time we have seen a juvenile loon give the introductory note of the male territorial call. In fact, Paul Strong just e-mailed me that the fledged chick on Long Lake in our study area did so as he watched from his canoe a few days ago. And we have observed chicks as young as six weeks of age emit truncated yodels after being released following banding. So we can see that young males — at least some young males — begin to yodel during the first three months.

Between fretting over the nest location, worrying about black flies, rejoicing over the successful hatch, and tracking the growth of chicks over weeks and months, it has been a busy summer for Shirley. She might have been forgiven if she had wrinkled her brow and left it at that when foreign juvies started arriving on the lake for snacks. Thank goodness she kept at it. Her tireless and meticulous loon observations have shed light on both pre-migration feeding patterns of young loons and a truly unknown pattern — behavioral development of the territorial call.

* “Clune”, Linda Grenzer’s and my favorite male loon, first settled on Deer in 2003. He was then only 5 years old. He and his mate reared chicks there in 2003, 2004, and 2005. But after a run of failure from 2006 to 2008, Clune evicted the male on neighboring Muskellunge and settled there.

** It is Lonn (Sharon in the background) who is pictured in Linda Grenzer’s beautiful featured photo.

*** We have learned quite a lot about the movements and feeding patterns of juveniles in the fall months.

on

If aliens landed on Earth’s surface to investigate its life forms, they would be puzzled by the coexistence of common loons and humans. True, loons spend almost their entire lives on the water, where they are relatively free of dangers from humans and other terrestrial vertebrates. But loons require solid ground for nesting, safe “nurseries” for rearing their chicks, and abundant food to keep themselves and their chicks alive. How, then, can loon populations persist along the southern periphery of the species range, where humans and human recreation threaten all three basic requirements?

The ability of loons to thrive in regions of intense human building and recreation vexed me for several years in the 1990s, when I first began my long-term loon research. I could see that most people venerated loons and took pains to protect them. But the sheer abundance of humans surrounding, approaching, and fishing near adults and chicks during the spring and summer made the tasks of hatching young and rearing them to adulthood seem daunting. How did loons manage to raise any young in the northern U.S. and southern Canada?

I cannot answer this question completely. I am still amazed at the abilities of adults and chicks on busy lakes to dodge motorboats and jetskis as well as they do. And it continues to surprise me when adults fledge chicks from small lakes where food seems limited. However, detailed study of loons’ nesting patterns allowed me to solve one riddle: how loons enjoy high nesting success despite intensive shoreline development.

One would think that shorelines are essential to nesting loons. Loons have to nest along shorelines, right? And humans build summer homes along shorelines too. So loons and humans would seem to be direct competitors for shoreline habitat. But it is not so. Why not?

The answer is deceptively simple. Well-drained “upland” shorelines provide the best sites for building lakeside homes. Upland sites are free of boggy or marshy vegetation. At the same time, upland shorelines provide poor nesting habitat for loons. Most loon eggs placed on upland shorelines end up in bellies of raccoons that take advantage of the comfortable footing they provide to look for easy meals. Experienced male loons learn to avoid placing nests on dry, upland shorelines.* Instead, they usually locate nests on islands, marshes**, or bogs hard for terrestrial predators to reach.*** So one key to loons’ ability to coexist with humans is merely loons’ preference to nest where humans cannot build.

Hodstradt Lake in the Wisconsin Study Area illustrates the complementary use of shorelines by loons and humans. Hodstradt is a 119-acre lake that has beautiful clear water with a slightly greenish hue. The lake is full of fish but completely encircled by lake homes. There is no island, marsh or bog in Hodstradt — only a peninsula in the southeastern corner (see screen grab below from Google Earth). Almost all nesting attempts by loons on Hodstradt have been on the end of that peninsula. High water caused by heavy rainfall in the past decade submerged the narrow spit connecting the end of the peninsula to the mainland, making it a small island. Whether an island or a peninsula, though, the land is low lying and impossible to build on. Hence it provides permanent nesting habitat for loons that is off limits to humans.

A similar situation exists for many loon pairs in the Minnesota Study Area. The seven pairs that nested this year on massive Cross Lake provide a good example. Three of these pairs nested on small uninhabitable islands; three nested among dense cattail patches in marshy coves; and one used an artificial nesting platform. (Five of these pairs hatched chicks.) Thus, the “Jack Sprat” nature of loon and human shoreline use can be seen in both Wisconsin and Minnesota. With rare exceptions, sites safe for loon nests are sites where humans cannot or will not build.

So adult loons are able to put chicks in the water despite extensive shoreline development. This would seem to be cause for celebration. In a cruel twist, though, shorelines altered to support suburban-style homes, lawns, and driveways have increased runoff. Although we are still working out the details, it appears that higher runoff has, in turn, produced a decline in water clarity and decreased chick mass, probably because adults cannot see fish well enough to provision their chicks adequately. In short, shoreline development negatively impacts loons during the second critical breeding phase: chick-rearing. Indeed, the sharp increase in mortality of chicks and young adults in the past two decades has become our number one concern with respect to the Upper Midwest loon population.

If there is a silver lining, it is this. Loons are resilient. They have been able to find nesting sites and sustain a high hatching rate despite everything humans have thrown at them. Perhaps we can help loons reverse the decline in chick survival, if we can learn precisely what is driving the drop in water clarity. This will be a massive challenge. But I have to believe that loons can come back from this setback. It keeps me going.

* We learned 16 years ago through marking of loons and systematic tracking of nest placement that male loons choose the nest site. For those not interested in looking at the science, we know this from two facts. First, loon pairs learn where to nest by trial and error. That is, they tend to reuse a site where they hatched chicks the previous year but move to a new nest location after egg predation. This logical nesting strategy is called the “win-stay, lose-switch” rule. Second, loon pairs in which the female pair member returns from the previous year but the male pair member does not usually do not reuse a successful site from the past year. In contrast, pairs consisting of the male from the previous year and a new female tend to reuse successful sites. In short, pairs with new male members do not use the win-stay, lose switch rule. They act as if they have forgotten where the best nesting site is.

** The featured photo is of Clune, Linda Grenzer’s favorite male loon, who bred for many years in her lake in Wisconsin. He is incubating eggs in a marshy corner of the lake that, predictably, is devoid of homes.

*** Of course, humans often accomodate loons’ nesting preferences by placing artificial nesting platforms along lake shores. Platforms provide very attractive nest sites for loons.

on

Loon pairs experience many setbacks during the course of a breeding season. Black flies drive them off of nests in May. Eagles take chicks. Intruders force them to expend energy in territory defense or even evict them. Rainfall clouds the water, making it difficult to find food for chicks. It is largely a pair’s ability to bounce back from such adversity that determines how successful they are at fledging young.

The loons at Big Trout-Far West, part of the Whitefish Chain, faced more than their share of challenges this summer. All seemed good in May, as the pair shared incubation duties on their two eggs (see photos above by Karl Olufs*). When they hatched two healthy chicks on June 9th, the veteran male and female breeders seemed poised for a fruitful year. But their luck turned. On June 12 a freak storm dropped golf-ball-sized hail to across much of the Minnesota Study Area. One three-day-old chick took refuge under a camp’s pier, while the second remained out in the chop. Following the storm, the exposed chick was found dead on shore, and only its sibling remained. In a poignant moment, one of the parents left the water and sat on shore beside the deceased chick, before returning to tend its surviving sibling.

Three-and-a-half uneventful weeks passed, and the surviving chick grew. On July 6th, though, the male, who had been healthy the day before, died suddenly and violently, a likely victim of a boat or jetski collision. For a few days, the female cared for the chick alone. But a new unmarked male soon noticed the lack of a male defending the territory and joined the female. Unwilling to rear a chick not his own, the new male grabbed the chick, shook it violently — as a horrified lake resident looked on — and killed it. In a month’s time, the original family of four had been reduced to one.

When Richard Rammer and I visited the Far West pair on July 26th, they were resting quietly in their marshy cove, as if in recovery. The female cooed repeatedly to her new mate, trying to coax him to search for a nest site. He sat quietly a few meters away, unmoved. There was something touching in the female’s stubborn unwillingness to accept defeat. Battered as she was by misfortune, she was looking forward — seemingly determined to lay the groundwork for a successful 2025 breeding season.

As horrid a year as the Far West pair had, they are only one pair. Elsewhere on the Whitefish Chain, the news was better. The pair at Island-Channel, which adopted a doomed chick in June, still had both their biological chick and the fostered one. Despite the apparent vigor of both chicks, I had nagging concerns. Was the biological chick getting more food? Were the chicks still bickering? The scale told the story: both chicks weighed in at a strapping 2.42 kilograms on the night of July 20th, when we caught the entire family.** Their future looks bright. Good news emerged too from a second pair on Island Lake, which abuts the Island-Channel territory. There an unmarked pair have raised a chick to five weeks of age and are likely to fledge it.

Even on Big Trout, where boat traffic is constant and rapid, a glimmer of hope emerged. Big Trout-Central, a few miles east of the ill-fated Far West pair, has raised a chick that recently turned five weeks of age. If it can dodge boats, jetskiers, and eagles for the rest of the summer, it will be the first fledgling from that territory since 2020.

Cross and Rush Lakes each contain three breeding pairs with chicks. The total of eight chicks between the two lakes is mediocre, considering the dozen territories they support. Still, among the chicks is a singleton produced by an all-new Rush-Boyd pair that bounced back from a chickless year in 2023.

Daggett Lake had an off year. Neither the Northeast nor Southwest pair hatched eggs, while the Channel pair hatched two healthy young from an island but lost them in the first two weeks. On the other hand, the Little Pine-Dream Island pair is enjoying their fourth consecutive productive season, raising two enormous independent chicks just north of the channel from Daggett. The news is also good from Pig Lake, where a new pair is raising two huge chicks after an off-year in 2023. The pair on Bertha, chickless for the past three years or more, also has two gigantic eight-week-old chicks. Sadly, the Upper Whitefish-Steamboat pair lost two small chicks in the same freak storm that cost one of the Far West chicks its life. But two of four pairs on Lower Hay (Northeast and Southeast) have chicks that are fit and strong. By raising a chick this year, the Northeast pair broke a slump of at least three years without young.

Loons in the Outing/Fifty Lakes section of the Minnesota Study Area, like those on Cross and Rush lakes, were only moderately productive. Roosevelt and North Roosevelt, between them, yielded only two fledged chicks this year. West Fox and East Fox pairs looked good early in the year. But the disappearance of the East Fox-South male resulted in loss of two chicks, in spite of the heroic efforts of the female to rear them alone. Furthermore, late loss of a large chick on West Fox-Stone Man whittled down the productivity to three chicks between the two lakes. Eagle Lake, similarly, yielded only one fledged chick. A mere two chicks emerged from Eagle, Kego, Butterfield, and Mitchell lakes combined this year, in contrast to the six produced in 2023.

There was a pleasant smattering of chicks on small lakes in the Crosslake region. Goodrich-West and -Southeast pairs both raised chicks successfully, and two new breeders on O’Brien beat all odds by hatching a late chick there. Kimble-East was a washout, but Kimble-West, Clear-North and -South, Star, Big Pine, and Grass lakes together raised eight chicks.

Lakes in the southwestern portion of the study area had an especially impressive breeding year. Ossie pairs raised five chicks in all. Pairs on Upper Hay, Nelson, Sibley-North and -South, Fawn, West Twin and the Cullens produced chicks at above-average rates, as did those on Roy-North and Roy-South and Nisswa. Pairs in the Upper Gull area did particularly well, including Mayo Creek, Boathouse, Bass Lake and Margaret-North pairs.

In short, the cruel summer at Big Trout-Far West did not typify the breeding season overall for the Whitefish Chain or the Minnesota Study Area as a whole. Stepping back to view the season from space, it was a decent breeding year. Low and short-lived populations of black flies early in the year helped get the season off to a solid start. Alas, the abundant rainfall we have had this spring and summer means that we cannot count on the continued paucity of these pests in 2025. For the moment, though, let’s shrug off the disappointment at Big Trout-Far West and enjoy the rather productive breeding year for loons in central Minnesota!

* Thanks to Karl Olufs and his sister, Janet, who paddled her kayak out to meet us on July 26th to relate the saga of the Big Trout-Far West pair.

** The male of the Island-Channel pair is an interesting loon in his own right. Hatched in 2016, he is among the handful of loon chicks marked with silver numbered bands by Kevin Kenow of USGS. Upon his capture, we read the number etched into his band and discovered that he was raised on the Big Island territory on Upper Whitefish in 2016. Thus, he is a whippersnapper at 8 years of age. He is the first known-age loon to settle in the Minnesota Study Area.