Walter Piper

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Loon calls seem to demand our attention. And sometimes they affect us emotionally. So it was this spring as I sat in a canoe with Sophia on the Blue Lake-West territory. While mopping up lakes after the pre-breeding census, we found the 16-year-old Blue-West female, W/G,B/S or “White-Green”, alone. Her behavior was ordinary, for the most part; she foraged, rested, and preened. Yet every few minutes, as if guided by an unseen hand, she lifted her head skyward and emitted a loud wail whose declining pitch seemed to convey profound and irredeemable sadness. Clearly her mate from the previous season was gone, and no male had stepped in to fill the vacancy. Indeed, White-Green spent the spring alone and still had found no partner in mid-June, long after the window for nesting with a new mate had closed.

White-Green was not alone in her solitude. On the following day Korben and I found the female on Hilts Lake, “White-blue-Silver”, nervously hanging out in the northwestern corner of that small lake. She foraged cautiously, unable or unwilling to drive off an intruder that foraged at will in her territory. She too found no mate with whom to breed this year. Having observed two openings for male breeders at the beginning of the year, I started to wonder if I was seeing a pattern.

I was chagrined to observe one of my favorite males, Green over Green, White over Silver (i.e. G/G,W/S or “Green-Green”) caught up in the male troubles that seemed to typify 2025. In 2015, when he took over Flannery, he created headaches for the resident female, who was rearing a chick on her own after losing her mate suddenly. But in the decade that followed, Green-Green became the steady, unflappable presence that his father was on Townline1. I smiled each time my schedule called for me to visit Flannery, knowing that I would get to check in on this tame, accepting male. But this spring, a few days after finding males missing on Blue-West and Hilts, I failed to locate Green-Green on Flannery. Instead, I followed his mate as she foraged throughout the lake. Every few minutes, she wailed pitifully — just as the Blue-West female had done. I took her behavior as a sign of Green-Green’s likely disappearance. A week later, however, Anna found Green-Green on Flannery behaving normally but reported that his left eye was cloudy. He remained on Flannery for the next month. But on July 13 he was found incapacitated by lake residents. Linda and Kevin Grenzer captured Green-Green and took him to REGI for treatment. Nine days later he seemed recovered and was released on Boom Lake. That was the last we heard of him until three days ago, when I got a report that his carcass had been recovered on the north shore of Washington Island on Lake Michigan. His presence there showed that he had recovered well enough to make a long flight east in preparation for his southward migration. We cannot be certain how he died, but his neck had a deep wound, which might indicate a prop strike. Life moves on, of course, but I am not looking forward to my next visit to Flannery, as I used to.2

The news was even more disheartening for the North Two male, “Red-Blue” (R/B,Ts/S). This tame 18-year-old loon — a veteran breeder that claimed the lake in 2014 — beached himself in early July. Linda and Kevin netted Red-Blue and took him to REGI also (see photo above, courtesy of REGI). He did not look terrible at capture, except that his right wing drooped. But he slid downhill rapidly and passed away within two days. The sudden appearance of necrotic tissue without other symptoms led REGI to conclude that he might have been electrocuted, perhaps through an ungrounded wire associated with someone’s dock lights. Naturally, his death was another blow. Despite the dearth of good nesting habitat on North Two, Red-Blue had raised four chicks during his eleven years on the lake.

Bad news comes in threes they say. So it was with a sense of inevitability that I learned recently of the third death of an established male during the breeding season in Wisconsin. G/S,Ar/Y (“Auric Red-Yellow”) was a skulker. My memories of Auric Red-Yellow are chiefly from capture nights. His was the ghostly black and white form that would take shape in the distance at night after we had motored slowly down sinuous, weed-choked Jersey City Flowage and spotlighted what seemed like ten thousand mallards lurking in patches of lily pads. But he was a successful parent, having fledged nine chicks with his even-more-skittish mate: Silver over Pink, Green over Green. Auric Red-Yellow was found dead on shore and emaciated, having ingested some form of metal. A vet must confirm this, but it seems that he swallowed someone’s lure, lost the ability to feed himself, and died of starvation.

Preoccupied as I have been with loon capture and marking, wrapping up the field season, and starting a year-long sabbatical, I have had difficulty processing the flurry of male mortality. I hope that the three males lost mid-season will be replaced by youngsters who had been waiting for their chance. After all, that is the way of things. Yet loss of male breeders does not always happen smoothly — or at all. The disappearance of our much-beloved male, Clune, from Linda Grenzer’s home lake in spring 2023 has resulted in three years (and counting) without a breeding pair on Muskellunge Lake.

In fact, I find this recent loss of five established male breeders profoundly unsettling. I have pointed out before that males are the limiting sex in loons. That is, males live shorter lives than females, and this tilts the adult sex ratio towards females. Put simply, males are in short supply, while there are ample females to fill breeding positions. Males have also been impacted by loss of water clarity. They, like chicks (and unlike females) are of substantially lower mass now than 20 years ago. As the “weak link” in the population, males seem most likely to be the cause of further population decline. Does the loss and lack of immediate replacement of these males this past season signal the beginning of that downturn? I hope not. But the pitiful wails of the solitary Blue-West and Flannery females after losing their mates made this year’s loss of males especially poignant and the memory hard to shake.

1Although there are many finalists for the honor, my all-time favorite loon was the old Townline male, Silver over Red, Orange over Green (S/R,O/G). “Orange-Green” was a doting dad who cranked out 20 chicks with five different females during an incredible 24-year run on his tiny lake just west of Rhinelander. Banded as an adult in 1994, Orange-Green seemed uncertain at first about his role on the Loon Project. Each time we launched our canoe and approached to take data he would eye us suspiciously for a moment and then relax, as if recalling that we were just those canoeists that liked to hang around with him and his family during the summertime. I was sad when Orange-Green did not return in 2018.

2The only good news to report regarding this episode is that another local male — this one an eight-year-old who was raised on Emma Lake and who made failed nesting attempts on Sherry and Hook lakes recently — is showing signs of claiming Flannery for his own and settling in with the breeding female. If he does so, the Flannery female — a pleasant, tame individual whom we banded as an adult in 2021 — will have no more reason to wail.

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There are several moments each year when I find myself out on a lake at night during capture season and suddenly think I must be insane. One such moment occurred at about 2 a.m. last night in Minnesota. Richard was driving the motorboat; Owen and I were perched in the bow scanning for loons. We swept the spotlight back and forth, back and forth across the dark surface of East Fox Lake. But we spent very little time in contact with loons. Our spotlight mostly caught dense, swirling tendrils of fog hanging in the air. Occasionally we broke free from this suffocating cloud for short intervals and the spotlight suddenly gave us an unobstructed view of 100 yards in every direction. Fortune was not on our side, however. We saw no loons in parts of the lake that were free of fog.

Loon capture — even loon-spotting — seemed highly improbable under these circumstances. I looked back at Richard behind me and Owen to my left. Their presence somehow reassured me that what we were doing — trying to locate a family of diving birds in total darkness and pea soup fog on a 241-acre lake so that we could lure them close to the boat with imitated calls and scoop them up in a muskie net — qualified as rational behavior. We searched on, fruitlessly. “Kill the motor Richard”, I said finally. “Let’s try playbacks.” Yet the loon pair at East Fox-South and their two 7-week-old chicks did not give away their position by vocalizing in response to our crisp recordings of wails from Maine and yodels from Michigan. Maybe it was regional bias.

We continued stalking the silent loon family. I directed Richard to steer right or left, so as to remain within the loon pair’s favorite part of the territory. Fifteen, twenty minutes passed. As our hopes of finding the family were beginning to fade, we caught sight of two black loon heads ten yards apart, partially obscured by a fog bank. “We need the unbanded male”, I reminded Owen. “Okay”, he whispered good-naturedly. With the two adults separated, we could not determine which was larger, forcing a split-second decision. Owen spotlighted the nearer adult. As we drew close to the bird, however, we realized our mistake. “Banded!” we both shout-whispered simultaneously. Owen swiveled the light quickly to the male we wanted. We crept up to him, while I imitated the scratchy whistled call of chicks in an effort to freeze him on the surface. At first, we were hopeful. The male did not shrink from the spotlight, as many loons do, and he was interested in the chick call. Alas, though, he was an unpredictable diver. He remained near the surface where Owen could track him with the spotlight, yet he swam first at — then underneath — the bow of the boat. I could not get the net in the water to catch him. After a minute or so, he vanished into the mist.

Moments later, the female wailed to our left. “Let’s go for her”, I told him, and soon after I had scooped her into the boat and — with Richard’s help — Owen had tucked her neatly into a padded, ventilated box. “Maybe the male will find the chicks”, I said hopefully. It was a reasonable expectation. We had seen the sole parent seek out the chicks many times before, once we had removed its mate from the water. And an adult swimming with its chicks is usually highly protective of them and less apt to dive. But we did not blunder into the male and chicks after that first encounter, despite 20 more minutes of puttering around in a cloud.

We gave up, motored to shore with the female, took a feather sample and blood drop, weighed her, and released her off shore. It had been a frustrating middle of the night boat ride on East Fox. We had failed to catch the bird we had targeted on the South territory. Yet we had banded four new chicks earlier in the evening — including two on socked-in East Fox Lake — and recaptured three adults. That brought our two-state tally to 40 unmarked adults newly banded, 88 chicks banded, and 27 adults recaptured. Looking back, we had quite a lot to show for our labors this July, considering that we face variable weather conditions, unpredictable study animals — and engage in an enterprise that seems to verge, at times, on outright insanity.

Pictured are Cora from the Minnesota team and Korben from the Wisconsin team.

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Twenty years ago colleagues and I published a paper showing that artificial nesting platforms increase loon’s hatching success by 70%. Others have reported similar patterns. So there is no doubt that, on average, loons that incubate their eggs on artificial nesting platforms (“ANPs”) put more chicks in the lake than do pairs using natural sites. Moreover, our paper showed that greater hatching success produced by ANPs also leads to more fledged loons.

In the last two decades, ANPs have become an enticing tool used by loon conservationists to boost loon populations. This is not surprising. ANPs have proven to be effective, and they are rather easy to make and place in the water. So conservationists can plop a mess of ANPs in the water and feel pretty confident that they have added young loons to the population. And they can make a strong case to funding agencies that their actions might help loons avoid population decline. Indeed, many millions have been/are being spent in the U.S. to float ANPs as a means to mitigate the negative effects that oil spills in the Gulf of Mexico have had on the species.

Are ANPs really just as good as natural sites at producing young loons that reach adulthood? Or are platform-raised chicks not as likely to survive to fledging age as chicks hatched as natural sites? We must remember that loons pick the location of a natural nest, whereas humans choose the site where platforms go. So it seems quite plausible that platform-raised young face hazards that natural-raised young do not.

It is only now that I have large enough samples of nests from platforms and natural sites that I can run a head-to-head comparison. Despite my 32 years of Wisconsin data, only a small proportion of loons in the Wisconsin Study Area (e.g. 15 of 90 focal pairs in 2024; 17%) nested on platforms. In Minnesota, however, almost half of all of our focal pairs use ANPs (38 of 84 territorial pairs in 2024; 45%), so our sample of platform-hatched chicks has swollen markedly since 2021.

As the graph above shows, hatchlings from platforms are lost slightly more often than are natural-hatched chicks in both states. While the pattern shows up in both Minnesota and Wisconsin, the difference is quite small and does not reach statistical significance. In other words, we have no scientific evidence that chicks hatched on platforms suffer lower survival than those hatched at natural sites. The same can be said for chick loss in Wisconsin versus Minnesota, despite what appears to be a slightly higher rate of chick loss in the North Star State.

Frankly, I am relieved! It has become almost de rigueur to place an ANP in your lake to support the loons. If, for some reason, ANPs had been producing chicks likely to perish before reaching adulthood, it would have sent shockwaves through the world of loon conservation.

I am still not a great fan of nesting platforms. Why not? Because we have learned in recent years that nest predation is not the main problem loons are facing in the Upper Midwest. Remember, nesting platforms are a one-trick pony. They increase hatching success enormously and put more chicks in the water. But if chicks cannot get enough food to survive to adulthood or reach prime condition, then all of the platforms in the world will not help them.

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I am a nervous traveller. The day before I am scheduled to leave, I start to worry what could go wrong. Could I miss my flight? What personal items will I forget to pack? Which tasks on my to-do list will I leave unfinished?

So it was two days ago as I drove from the house where I had been staying to meet up with my Minnesota field team before flying home to California. I had spent the morning collecting data on territorial loon pairs — six on Ossawinnamakee, and one each on Fawn and Pig Lake. I relish every moment spent with loons, especially when I am on my own. But anxiety about getting my field work done, entering my data, and tidying up the place before my departure gnawed at me all day.

I tried to work backwards. Arrive at Brainerd Airport at 5:15, so leave from storage box at 4:30. Be at storage box by 4:00 to pack up canoes and check banding supplies for next month. Arrive at tech’s lodging by 2:30 to review field procedures and check in before my trip. Finish entering data in online database by 1:30. Tidy up lodging by 1pm. Leave my last study lake by noon.

When I set off to visit my techs on Ossie, I was still on schedule. As I began to round the hairpin curve on County Road 39 next to the Ossie boat landing, I thought: I just might make my flight. In a brain-staggering moment, though, I spotted an adult loon sitting on the shoulder on the east side of the highway displaying a clear intention to cross. “Oh no!”, I screamed, as I pulled to the side of the road and flicked on my emergency flashers. I ran across the highway and placed myself in the middle of the northbound lane, intending to block any traffic from passing close to the loon. As I crept cautiously toward this adult, I noticed two newly-hatched chicks huddling against it, trying to shield themselves from my view. “Oh no!”, I repeated.

Despite my shock at the loons’ predicament, I understood immediately what was happening. Six hours earlier Keith and Dawn Kellen had given me a tour of the six breeding pairs on Ossie. The Ossie-Muskie Bay pair had stumped us all spring. The Kellens had seen them together early in the year, had seen only one out on the water on multiple occasions thereafter, and yet neither they in their pontoon nor my team in our canoe could find a nest in the far east bay of the lake, adjacent to County 39. The pair had simply vanished. The sudden appearance of an adult and two small chicks told me that they had not nested on Ossie, where we had been looking for them, but on Rat Lake,

Location on County Road 39 where I found the adult male and two small chicks.

across the highway from Ossie’s eastern end. Thus, the Muskie Bay pair was in the awkward situation of seeking to nest on one lake and raise their chicks on another. That ambitious plan set them up for a difficult land crossing.

I had stumbled upon the loon family at the most dangerous point of their overland journey. The adult wailed and tremoloed as I stood in the highway 30 feet away. A southbound car and truck slowed down to rubberneck but continued by despite my frantic waving for help. My mind raced. I could not handle all three loons. If I picked up the adult, its flailing might injure the tiny chicks. Furthermore, the chicks might decide to strike out on their own across the road without their parent to guard them. I was not sure that I could discourage them from putting themselves in harm’s way while holding the adult.

Knowing that the field techs were a few minutes away, I pulled out my phone. “Call Owen”, I demanded of Siri. Owen answered in his calm baritone. But I screeched, “Drop everything and come to the Ossie boat landing. There is a loon here in the road, and I need your help!”. “On my way”, he responded.

While I waited for Owen, more southbound vehicles came by, each carrying a driver wearing a puzzled expression. But no one stopped. As I was debating the odds of getting help from a stranger, the panicked adult abruptly turned, lined himself up with the roadway, and began to run down the highway with wings flapping, leaving his chicks with me. I watched and listened in horror as his feet repeatedly thwacked against the hard pavement during this takeoff attempt and was relieved when he aborted it and skidded to a stop about 40 yards away in the southbound lane.

At that desperate moment, Mitch Carlson arrived in his pickup with his friend, Leo, and stopped in front of the grounded adult. Sensing that the window to save the loon family was closing, I scooped up the tiny chicks and marched hastily in Mitch’s direction (see photo below). He opened his door and looked at me questioningly. “Can you take the chicks?” I asked. “Okay”, he replied quickly, sensing my urgency and smoothly accepting them. He volunteered, “My wife raises chickens!”. I turned my attention to the adult in the road.

After his aborted takeoff attempt, the male loon sits in the southbound lane of County 39 while I approach carrying his chicks. Photo by Mindy Schenck.

Quick, decisive action yields the best results when capturing animals, I have found. When I drew close enough, I lunged at the rearing adult and managed to grasp it. I then folded its wings against its body, held it to my side, and did my best to fend off its bill. Meanwhile, Owen had arrived. I struggled towards the boat landing with him guiding me. Mitch followed with the chicks, while Leo walked alongside, gawking and snapping photos.

The chicks were so small that I was afraid the adult might leave them behind in its haste to put distance between us and himself after release. So I asked Mitch to let the chicks go, waited a moment, and gently

Mitch holds the two newly-hatched chicks moments before we release them at the Ossie boat landing. Photo by Leo Carner.

lowered the adult — which felt like a male based on size and ornery demeanor — into the water at the end of the boat landing. Fortunately, he dove, surfaced quickly, spotted the chicks, and promptly resumed his parenting responsibilities. It was an ample reward for Mitch and me to see them all together so quickly again in the middle of the lake.

The male and chicks reunited quickly after we let them go off of the Ossie boat landing. Photo by Leo Carner.

I will always be a nervous traveler. I do not think one outgrows that. And I need to put a schedule together to convince myself that I can meet a deadline. But perhaps on my next trip I will remember to include 30 minutes of wiggle room for unforeseen events.

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We face many difficulties in studying loons. They are aquatic. They dive and resurface far away when we approach them. They are gone for half the year. We can capture and mark adults only during a brief window when chicks are small. We cannot keep them in captivity, which limits what we can learn about their biology. Finally, loons are long-lived, so it requires decades to understand their life histories fully.

Back in 1993, when I informed her that I was about to begin a loon study, my postdoctoral advisor at Indiana University made a face. “Are you sure?”, she said. She was well aware of the difficulty of studying species like whales, eagles, tigers, and loons. These are beautiful, charismatic animals. But they are challenging to learn about scientifically. Was it wise for me, a young untenured academic, to embark upon a long-term investigation of a notoriously recalcitrant species?

No, it was not wise. But wisdom does not always guide our decisions. I felt drawn to loons. I also believed that the training I had received at Indiana, at Purdue, and especially from Haven Wiley, my PhD advisor at the University of North Carolina, had equipped me to ask rigorous, meaningful questions about the behavior of any animal.

When I first began my work in 1993, I recognized immediately that my greatest obstacle was going to be telling loons apart. This problem is familiar to behavioral ecologists. I had confronted it myself when studying wintering white-throated sparrows in North Carolina in the 1980s. But treadle traps allowed Haven and me to band hundreds of white-throats and recapture them at will. Moreover, we could see the bands on sparrows’ legs at all times.

Not so for loons. In most cases, we cannot identify an individual when it is resting on the water. Even when we have nailed the bands on both members of a breeding pair, we must reidentify each bird when it dives and resurfaces. (Every so often a loon has an oddity in its plumage or on its bill that sets it apart from other adults.)

Loons themselves must be far better at identifying others of their species than humans are. After all, if humans lose track of which loon is which during an observation session, we curse and make a few erasures on our datasheet. But a loon that mistakes an intruder for its mate might pay for the error with its life.

So it was with more than casual interest that Anna Alber and I entered the second phase of our analysis of loon appearance by computer. Could a computer learn to tell a large sample of loons apart visually? If so, then surely loons themselves can tell each other apart. A loon, of course, can base its identification not merely on appearance, but also on behavior and vocalizations.

Anna ran two trials. First, I identified 10 loons from Wisconsin and Minnesota for which we had at least 24 photos from a range of angles. Anna chose a set of “test” images of each loon in the sample and set them aside. She then “trained” the program to identify all 10 loons, using the remaining images. Upon testing, the computer correctly assigned 85% of Anna’s test images to the proper individual. Considering that pure chance would have resulted in a success rate of 10%, 85% seemed pretty good. In the next trial, we used 35 banded loons. This time I picked one test image for each loon, trying hard to select ones that closely resembled no other in the sample. In this go round, the program correctly identified loons at a 68% rate. Since random guesses would have resulted in a 2.8% success rate (1/35), Anna and I have begun to think that the computer knows what it is doing.

We found two additional patterns that shed light on the use of AI to identify loons from photos. First, in the cases wherein the computer correctly ID’d the loon in the test photo, it had 18.7 images to practice on beforehand, whereas the mean number of photos for misidentified loons was 11.5. In other words, when the computer had developed a good sense of what a bird looked like, it was better able to identify that loon later. Second, the computer was good at predicting its errors. In the 24 cases where it had ID’d a loon correctly, the computer’s average certainty of its guess was 81%. In contrast, the mean certainty of the computer for photos where it misfired was only 53%. And if we narrow the sample to instances when the computer had 90% certainty or more, it was right 12 of 12 times.

There is more work to be done in identifying loons from their photos. Phase Two, happening this year, will be to take photos of as many loons photographed last year as we can to see if the computer can use photos of a loon in one year to identify it in another year. This, of course, recreates the problem that male and female breeders across the Upper Midwest faced a few weeks ago when they returned to their territories and encountered an individual of the opposite sex. “Is that you?”

The photo above is by Hayden Walkush and shows the long-time male breeder on North Two Lake, near Lake Tomahawk, Wisconsin. Hatched and reared on Hodstradt Lake in 2007, this male settled on North Two in 2014 and has fledged four chicks on the territory since then. The Wisconsin Team found him back on North Two this past week, so he is back for another go!

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I love southern California. I truly do. Although it is disconcerting to look outside — or even step outside — and never really know what the season is, the weather is always beautiful here. The beauty of the region pales for me a little this time of year though. Why? Because we get curious, muted springs. True, Orange-crowned Warblers, House Wrens, and Bell’s Vireos have exploded into song. But it is only slightly warmer now than it was a month ago — and barely greener. The spring that I read so much about in the paper each day must be going on elsewhere.

Indeed it is. With ice off of our study lakes in Wisconsin and Minnesota, loons have returned to their territories. Most are reacquainting themselves with their mates of the previous year after eight months apart, foraging to recoup energetic losses from migration, and checking out potential nest sites.

But rest and recovery are not the only orders of the day for territory holders. The few weeks after iceout are a time of great peril. Young loons without territories probe those in their neighborhood for vacancies and weakness. These young adults try especially hard to seize territories where they observed chicks the year before. (Chicks on a territory are like a badge signalling its quality.) Breeders intent on holding their territories must invest considerable effort convincing young pretenders that an attempt to evict them would be costly and futile. Providing ocean conditions on the wintering grounds a few months before allowed them to prepare well for the breeding season, most territory holders do ultimately hold off all competitors and turn their attention to breeding.

Loons are not the only ones scrambling. With classes still in session until May 16th, I am stuck in California for two more weeks. While my Wisconsin and Minnesota teams are prepping for fieldwork, I am completing an endless stream of forms, contracts, online trainings, and other paperwork to help bring that about. On weekends, my wife and I ride our bikes toward the ocean and take in the mild greening and hint of warm weather that mark springtime in this part of the world. Yet a big part of me hungers to be on northern lakes, where spring arrives with a vengeance and loons fight tooth and nail for the privilege of rearing young for another year.

Sheila Johnston’s cool photo from this spring shows her favorite loon, Lena. Lena was a victim of an early-season eviction last May and spent weeks recuperating. We are delighted to see her back this year and re-paired on her old territory. With some luck, she and her mate will raise chicks on Upper Gull in 2025, just like the old days.

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In recent blog posts, I made the point that the course of a young loon’s life is more affected by its early experiences in Wisconsin or Minnesota than by conditions during its first winter in Florida. Winter happenings along Florida’s Gulf Coast do affect youngsters, but the amount of food they receive in their first several weeks of life makes an indelible imprint on their well-being.

One might have expected established breeders to show even greater immunity to winter conditions. Once an adult has claimed a territory, reared chicks to fledging, and survived several trips from the Midwest to Florida and back, what challenge is left that can threaten it? Can’t adult loons begin to “coast” a bit after these achievements? And if so, might the four months spent along Florida’s shoreline simply be a period of rest and recovery from the stresses of territoriality?

To some degree, established adults can coast. Having settled on a breeding lake at the age of 6 years or so, they have surmounted life’s greatest obstacle. Since senescence does not take hold until they are in their mid teens or 20s and since annual survival of loons in their prime is 94%, newly-settled breeders stand a good chance of holding their territories for a decade or more. But long-term ownership is never certain. The simple act of raising chicks exposes an adult loon to territorial challenges, because nonbreeders bent on claiming a territory use the presence of chicks there as a badge indicating its quality. So proud parents in one year pay the steep cost of increased territorial defense — and the risk of eviction — the next.

Recently we have learned an incredible thing. Ocean conditions that loons face during winter — whether they are 8, 11, or 15 years old — can reduce their body condition subtly such that they are prone to eviction from their territories several months later, when they return to the breeding grounds. Specifically, loons that have spent the winter in cold, dilute ocean water are much more likely to get booted from their summer territories than those that spent the off-season in warm, salty water. Here is what those patterns look like.

Fig. 1. Territory holders that experienced cold ocean water during the previous winter are more likely to lose their territory in a battle than those that spent the winter in warm water.
Figure 2. Breeders that encountered ocean water of low salinity were more likely to be evicted from their territories than breeders that had wintered in salty water.

An obvious question is this. Why is warm salty water beneficial to loons? Sadly, the answer is not obvious, although loss of salinity can be linked to increased runoff from rivers into the Gulf of Mexico, which reduces water clarity and can spawn phytoplankton blooms. (Both low clarity and increased phytoplankton are harmful to loons.) The negative impact of cold ocean water is also hard to interpret, but cold water forces loons (and other warm-blooded aquatic creatures) to expend energy just to maintain a high and stable body temperature. Perhaps the energetic hit that loons face in keeping warm in a cold ocean puts them at a long-term disadvantage.

We are not the first to discover that environmental factors in one season can impact animals in another. In fact, such “carry-over effects” are now known in several species of songbirds. Understanding carry-over effects is crucial to conservation, because they reveal the interconnectedness of the seasons. If the quality of a bird’s winter habitat limits when it can migrate in the spring, how successful it is at finding a territory on the breeding grounds, and the number of offspring it raises, then clearly we must take a holistic view to understand avian conservation.

From a territorial loon’s standpoint, poor ocean conditions in winter pose yet another challenge. It is bad enough that raising chicks puts a great big target on your back. We now realize that loons that encounter cold, dilute ocean water during a winter after rearing chicks will face a double whammy in holding their territory the following spring.

Our discovery of carry-over effects in loons might help us understand how the species’ odd system of territory eviction evolved in the first place. Perhaps natural and inevitable fluctuations in the quality of the winter habitat guarantee that some adult breeders will be vulnerable to takeover each year. If so, winter-weakening sets the stage for the evolution of territorial eviction as an effective behavioral strategy for claiming a territory.

We eagerly await the 2025 field season and have a very strong team in both states. However, field costs have mushroomed unexpectedly by a whopping $28,000. As it stands, we are $1,800 short of our goal of raising $20,000 to earn an additional $20,000 in matching funds from the Walter Alexander Foundation. If you are able, please consider helping us cross this threshold so that we can defray most of our field costs. Thanks so much to those who have already given!

The beautiful photo of the male is one of Linda Grenzer’s. It shows the Deer Lake male (B/S,P/R) becoming airborne during a takeoff run. Love that pink band!

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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!

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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.