Having just posted about our discovery that loons with chicks are in a desperate struggle to protect long-term territory ownership by hiding their own chicks and “spotlighting” neighbors’ chicks, I kept thinking: “That is pretty cool! How can I let others in science know about it?”

In looking for a suitable journal where I could submit our new paper detailing that finding, I came across the high-impact journal Frontiers in Ecology and the Environment. Our entire data paper turns out to be too long and the subject matter not appropriate for a full-length paper in Frontiers. But, while leafing through the journal, I saw that it also publishes 150- to 250-word blurbs accompanied by crisp photos that together describe an “Aha!” moment you had as an ecologist — a moment when you discovered some pattern that answered a burning question or opened up a new field of study.

That piqued my interest. Since I study the most photogenic animal on the planet and work with a talented photographer, I thought I would take a flyer, work up the nasty neighbor story, include a couple of Linda’s photos, and see what the journal said.

The writing was sheer agony. 250 words is a laughable number for explaining a tricky concept like spotlighting of neighbors’ chicks, because you have to introduce the species, explain the territorial system, describe loon chicks and their behavior, and — most challenging of all — explain the complex system of information-gathering by floaters and intrusions by territory owners that underlies the nasty neighbor story. I wore out my “delete” key writing this tiny, unbelievably dense piece.

But it was worth it. Less than 24 hours after I sent the blurb in, the editor accepted it. Linda and I are thrilled. I think my tofurkey will taste a little better this year! Sorry…..I am unable to show you the piece here because we have signed a form preventing that until publication. I promise to post a link as soon as Frontiers publishes it.

I often thank my lucky stars that I am a field biologist. Being outdoors, especially in Wisconsin, is a huge perk of my profession. There is something thrilling about being in a situation where nothing is planned and anything can happen. Yet as glorious as it is to be outdoors, field work is perilous. Although I might tell the National Science Foundation, or Chapman, or the U. S. Geological Survey (who provide leg bands) that I have much of loon behavior figured out — that I have systematically tested all hypotheses and eliminated all plausible alternatives — I never feel confident when I am watching loons. They invariably surprise you by doing something that defies explanation. “What does that adult have to gain from wailing so often and so loudly when there is no other loon nearby to hear it?” or “Why is that loon wasting time alarm calling at the harmless muskrat?”. Rarely does a day in the field go by when I do not scratch my head at least once at inexplicable loon behavior.

Paradoxically, the best place to be when you are trying to figure out why animals behave as they do might be in your office, crunching the numbers, without any animals in sight. Free of distractions and laser-focused on the data, sometimes you discover a pattern that gives you a clear answer to a central question.

That happened to me yesterday. I was puzzling over a weird finding. In the midst of analyzing patterns in territorial intrusion, I was surprised to learn that territorial loons intrude more often into neighboring territories with chicks than do young, non-territorial floaters that are looking to settle on a territory. How on Earth could this be so? Floaters are young adults that are on the prowl. They search widely for territories with chicks, use those chicks as a badge indicating a good territory, and then return to try and evict a pair member in order to seize the territory for themselves. So it is floaters, not territory holders, that should be obsessed with finding, visiting, and competing for territories with chicks. Territory holders should have as their priority simply holding onto the territory they already own.

I must point out here that intrusions into territories with chicks, regardless of which loons make them, are generally a bad idea. As many of you have seen, territorial loons do not appreciate landings or close approach by intruders when they have chicks to protect and are much more apt to attack intruders at such times. This fact only thickens the plot. Now we must try to understand why a territory owner — a loon with something valuable to lose — would take a chance at being injured by visiting a nearby territory with a super-aggressive owner!

Lacking any other obvious path forward, I dove even more deeply into the curious tendency of territorial loons to seek out neighbors with chicks. Late in the breeding season, territory owners can be partitioned into two groups: those with chicks and those without. So I could look to see if, as one might predict, territory owners that had failed to raise chicks — and who therefore might be looking to trade up to a better territory — were those most likely to intrude. But quite the opposite was true. Territory owners rearing chicks of their own were much more likely to intrude at neighboring lakes with chicks than were territory owners that had no chicks.

As it happened, I discovered this last vexing pattern late in the day and could not dwell upon it. At 2:32 a.m. — during that inevitable hourlong period of sleeplessness that comes each night — I figured it out. While successful rearing of chicks is the ultimate goal of an adult loon’s life, chicks pose a great hazard too. To a floater, a territory owner’s chicks signify a high-quality territory, and so chicks raised in one year guarantee the owner will spend the next year fending off eviction attempts from floaters. It follows that owners should take any and all steps they can to keep floaters from learning about their chicks. Simply decamping and leaving your chicks alone during early morning is a good strategy, because floaters learn about chicks chiefly after spotting their conspicuous parents on the water and landing near them. If you are not on your territory, then no floater is likely to find your hidden chicks. But being away from your own territory and also intruding into your neighbor’s territory is doubly beneficial for a loon with chicks, because your presence will draw other adults to the neighbor’s territory (and away from your own territory nearby) and increase the likelihood that your neighbor’s chicks will be the ones that are spotted. That is to say, neighboring pairs with chicks seem to be locked in a desperate, reciprocal effort to expose each other’s chicks to floaters in order to protect their own territory ownership.

As I write this, I am listening to the hideous whine of a circular saw next door. Our own neighbors have contracted with the loudest and most inefficient construction crew west of the Mississippi to renovate their home. I find the noise, the clutter, the truck traffic, and the ceaseless cursing and shouting tiresome, to say the least. But I am fairly confident that our neighbors are not conspiring with outside forces to get us evicted. So I guess we have it pretty good.

Several months have passed since our paper on the population decline in northern Wisconsin was accepted for publication. But the wheels of science turn slowly, and only just now has the online “issue” come out that contains our article. To accompany their published articles, the journal invites authors to publish also a blog post on the journal website, and I jumped at this opportunity to spread the word about the peril that my study population now faces and its particular meaning to me.

Rather than repeating that blog post here and incurring the wrath of the journal, I will include this link. The article itself is freely accessible to the public, according to the website.

Sometimes, as a scientist, I get tunnel vision. I get so locked-in while running statistical tests to verify simple behavioral patterns that I cannot see beyond those patterns.

This past week, I got another illustration of the problem. I was asking a basic question: “Do territorial loons show stronger territory defense when they have chicks than at other times?”. We might expect such a pattern for two reasons: 1) young chicks are sometimes killed by “rogue” intruders, and 2) intruders learn that a territory is of high quality — and possibly worth fighting for later — from seeing a chick or chicks in it; so territorial pairs should hide their chicks from intruders. As stated, this question is binary; I am just asking if the chick-rearing phase is characterized by more intense territorial behavior than other phases of the breeding cycle (like the pre-nesting and and incubation periods). And there is nothing unsound about asking that question. It is just a bit narrow.

I didn’t see the limitations of the question until I plotted the data on territorial defense against stage of the breeding cycle. Here are those data.

At first glance, I suppose, the graph looks a little busy. “Why did he have to plot TWO lines on a single graph?”, you might ask. My goal was to allow the viewer to compare two kinds of territorial behavior towards intruders at once: 1) territorial yodels by males and 2) outright attacks of intruders and other forms of physical aggression — and to look at how those behaviors vary throughout the breeding cycle. The graph allows us to see not merely how territory defense varies when territory owners have chicks or do not have them, but how territory defense changes throughout the breeding season — from 20 days before the eggs hatch to 50 days after.

What do we see? Whereas the statistical analysis I did simply told me that both yodels and aggression are more likely during chick-rearing than at other times, the graph paints a more nuanced picture. First, we see that yodels spike sharply at hatching and are rather infrequent at other times (red line). That is, males yodel with surgical precision during the period when their chicks are less than two weeks old and seldom at any other time. In contrast, aggression (blue line) by male and female parents peaks much later — when chicks are three to six weeks old. In short, territorial pairs seem to employ yodels and aggression for different purposes.

Here is my interpretation. As a grad student of mine showed experimentally, yodels are effective tools for discouraging landing by intruders that have entered the airspace above a territory. By yodelling, a male can cause an intruder bent on making a territorial visit to change its mind and visit elsewhere. Frequent yodels by males with tiny chicks, then, keep intruders away from chicks when they are small and most vulnerable to being killed by territorial intruders. But if intruders are so dangerous to young chicks, shouldn’t territorial aggression also be very frequent at this time? No, it should not. Yodels are so effective at driving intruders away at this time that few intruders approach pairs with young chicks closely enough for aggression to be necessary! Instead, it seems, parents only need to defend their chicks with physical aggression when this critical stage has passed, fathers have stopped yodeling their heads off, and intruders are comfortable enough to land in a defended territory and engage in social behavior with territorial pairs.

As I was strutting about the house and congratulating myself for solving this small puzzle, I presented the idea to my wife. She inspected the graph and asked a very reasonable question: “Why do males stop yodelling?”. After making a mental note never to share my ideas in the future, I puzzled over my wife’s vexing but insightful observation.

Here is my tentative response. We know from Jay Mager’s work that yodels are costly. Why? Because, by yodeling, a male is telling young nonbreeders about its identity, size, and body condition. Such information might allow those young adults to decide whether or not to try to evict the male from his territory immediately, to do so at some point in the future, or never to try. So yodels betray valuable information about the yodeller that might best be hidden. In particular, a small old male that has fallen into poor condition is placing a great big target on its back by yodeling to protect his chicks. Since yodeling males keep intruders at bay — a short-term benefit — but are also giving away valuable information — a long-term cost — males should use this potent vocal weapon only in time of greatest need.

Now……that is just so much arm-waving. I have conveniently tailored my hypothesis about the laser-targeting of yodels to the observations we have made. But at least, by developing a testable hypothesis, I have laid the groundwork for future progress. One day experimental playbacks of yodels at different stages of the breeding phase — not just at the young chick stage, where they normally occur — will determine whether the hypothesis has merit. So it goes with science.

Among the most curious and talked-about aspects of common loon behavior are “social gatherings” — groupings of three to twelve adults that occur in July and August, which feature loons swimming together and interacting socially for an hour or more. During social gatherings, adults exhibit stereotyped social behavior, such as circle-dancing, bill-dipping, excited peering, and splash-diving. Occasionally one loon lunges at a second, which touches off a point-yodel by a male or two and fleeing across the water by a few panicked participants. If the gathering is on a territory with chicks, those chicks hide near shore, while their parents swim with their adult visitors. However, as shown in Linda’s photo (above; the observer is Nelson Gould, who spent two years helping run the Project) and my video (below), the most frequent and obvious behavior seen in social gatherings is what appears to be relaxed, slow, joint swimming by a large raft of adults. Peaceful swimming of this kind could be described as the hallmark of social gatherings.

Of course, it is tempting to offer a simple, unitary explanation for social gatherings. I have been asked a number of times whether the visitors at social gatherings might not be chicks that were hatched on reared on a lake and have returned as adults to re-connect with their parents. Setting aside the fact that young adults looking for a territory would seem to have little to gain from visiting their parents — and might even harm their parents by drawing more attention to the territory (see below) — we have many marked loons of all ages in our study area and can look at the number of times that young adults have revisited their natal lakes. Of 1743 visits to lakes by adults that we marked as chicks that we have recorded so far, only 13 have been visits to the natal lake. We have not yet run statistics on this pattern, but it seems clear already that young loons actually tend to avoid their natal lakes — intruding at many lakes in the neighborhood but seldom visiting their natal one.

A second common speculation is that social gatherings are mere aggregations of birds for foraging purposes. But, as Jim Paruk has noted, foraging rarely occurs at social gatherings. Finally, social gatherings are sometimes described as being groups that form in anticipation of migration; but gatherings occur in late summer, not fall, so they happen far too early to be a prelude to migration.

In fact, a crucial first point to grasp as we seek to understand social gatherings is that participants in these events comprise a hodge-podge of adults with competing interests. In other words, the key to understanding social gatherings will lie in understanding their makeup. Therefore, we will be powerless to solve the riddle of social gatherings without a large population of marked birds, including both territorial adults and young intruders.

The first set of participants in social gatherings are simply territorial pair members defending the lake where the gathering occurs. If this “home pair” has chicks, the intruders within the gathering are unwelcome guests, and the home pair’s chief goal is to steer the intruders away from their chicks and make sure they do not stay too long. Why? Because nonbreeding loons that are part of the gathering try to find chicks, use the presence of chicks as a badge indicating the quality of the territory, and often return to evict owners on lakes that produced chicks the previous year. Home pairs that have failed to produce chicks probably also benefit from limiting the duration of gatherings, so as to protect their territorial position. (However, we have not verified this last hypothesis statistically.)

A second set of participants in social gatherings — the largest segment — are nonbreeders who seek information for future territory settlement. Unlike others who have tried to explain social gatherings, we on the Loon Project are in a unique position to describe this important segment, because we have been marking chicks in our study area for over twenty years and these marked chicks have returned as adult nonbreeders in many cases. Thus, we know that nonbreeders are: 1) adults two to four years old that are too young to settle on a territory, or 2) individuals five to ten years old that are in prime condition and on the brink of territory settlement, or 3) adults of various ages that have been evicted from a previous territory and are looking to resettle on a new one. Again, all nonbreeders have in common that they are learning about a variety of territories in a certain region — chiefly which have chicks; which do not — in order to settle on one of them, usually by evicting a territorial owner. So nonbreeders are a particularly dangerous segment of the loon population, from the standpoint of home pairs.

The third cohort of attendees, and perhaps the most interesting, consists of neighboring territory holders. These adults, which may or may not have chicks on their own territory, at least have a territory and therefore obviously have reasons very different from nonbreeders for joining the gathering. Since they have left their own territory undefended to make the flight to this neighboring lake — and often their chicks, as well — it seems clear that neighbors must gain something from the visit. The most plausible explanation for participation by neighboring pair members is that they are trying to draw nonbreeders in the neighborhood to someone else’s lake instead of their own. Neighbors seem to be exploiting the fact that adult loons of all stripes are strongly attracted to other adults that they see on lakes. In decoying nonbreeders to another lake near their own, neighbors are decreasing the odds that their own chicks hiding back on their lake will be discovered, while increasing the chance that the home pair’s chicks will be seen by nonbreeders. From the home pair’s standpoint, then, neighbors are competitors whose visit is potentially harmful in the long run, but at least they pose no threat to territory ownership.

I will have more to say about social gatherings. Indeed, I am currently analyzing and comparing the behavior of territorial pairs and intruders at social gatherings. So I will have further findings to share in the coming weeks. For now, try to keep in mind the key point of this post: loons in social gatherings constitute a broad swath of individuals that differ in age, territorial status, and current reproductive stage. Although the behavior of all participants might look similar during the gathering, each loon has its own goals in attending the event and its own hopes for the outcome.

In the interest of full disclosure, I will admit that I am grouchy. In the past five days, we have lost three adult loons from our study area. The first of these was the Arrowhead Lake male who, having broken his right wing in early July, finally succumbed to that injury last Friday, leaving his mate and two almost-grown chicks. We all knew that the Arrowhead male was going to die before the end of the season, but it still hurt when his lifeless body finally washed ashore.

The second loon that we lost was an adult male found in the eastern part of Minocqua Lake. He was unbanded, and the only unbanded male we know of from that location is the territorial male from the Minocqua-East territory, who nested unsuccessfully with his mate in the thoroughfare to Lake Tomahawk in May. So we are fairly confident that this male is from Minocqua-East. On Saturday he became incapacitated, beached himself near the Minocqua boat landing, was reported by lake residents, and was picked up in this defenseless condition by Linda and Kevin Grenzer, who took him to Raptor Education Group, Inc. Linda and Kevin could tell from his green droppings and lethargy that he was likely a victim of lead poisoning, and their suspicion was confirmed by a blood test at REGI on Saturday. The folks at REGI started chelation treatment to remove the lead from his blood, but their efforts were too little, too late. A large male weighing about 4.5 kilograms when he was healthy, he had wasted away to 3.1 kg at his death.

Male from Katherine Lake on Lake Michigan. Photo by Christopher Rocke.

The third death of a male loon from the study area occurred just a day later. On Sunday Chris Rocke e-mailed me to say that while paddle-boarding on Lake Michigan, he had run across a marked loon that stayed very close to shore (see his photo, above) and seemed reluctant to dive. He became concerned about the bird’s odd behavior and listlessness. Over the few days that Chris watched him, this loon became weaker and weaker, to the point where Chris was able to capture him by hand on Sunday afternoon. His bands, photographed by Chris, below, showed that he was “silver over red, taupe-stripe over red”, an individual that we have come to know well over the

years. First banded in 2004 on Lake Seventeen with his mate and two chicks, this male and the four females he was paired with during his breeding career on Seventeen cranked out eight offspring before his eviction in 2014. He then relocated to Katherine Lake, where he nested unsuccessfully for six straight years. This year, he and his mate failed in a way that we had not observed previously — first one of their eggs and then the other rolled off into the lake, because the nest had been placed on a slope near the water. Still, this male’s breeding success on Seventeen made him one of the most productive breeders in the study area. Like many loons from the Upper Midwest, he was making a stop on Lake Michigan prior to completing his migratory journey south.

Once I learned that Chris had found one of my oldest and most familiar study animals in a compromised condition, I urged him to take the loon to an animal rescue center. Chris and his partner, Leva Engel, interrupted their Labor Day vacation, drove the Katherine male over an hour towards Antigo, and dropped him off with Linda and Kevin Grenzer, who completed the trip to REGI. As the featured photo shows, it was deja vu for the Grenzers: another limp, lethargic loon. This condition, together with his greenish feces, pointed again to acute lead poisoning, a diagnosis confirmed by blood test. Like the Minocqua male that had died the day before, the Katherine male’s lead concentration was so high that it could not be measured precisely. The Katherine bird had wasted away from 4.4 to 2.8 kg in a period of a week or so, owing to his inability to feed himself. After several seizures yesterday (another symptom of lead poisoning), he passed away overnight.

If lead poisoning were a freak occurrence, like a lightning strike, we could justifiably shrug and move on. We cannot protect loons from lightning strikes. But a clear pattern has developed in northern Wisconsin: many adult loons die each year from acute lead poisoning, when they ingest lead sinkers, usually on fishing lines. Loons can survive ingestion of fishing tackle. In fact, their powerful digestive systems have been shown to grind up steel hooks and swivels. Lead is different. Lead kills loons, eagles and other wildlife that swallow it, because it has rapid, powerful effects on the brain and nervous system and cannot be quickly broken down or expelled by the body. And most loons that ingest lead fishing tackle are not reported by humans until they are so weak that even extreme measures taken by veterinarians cannot save them.

Consider this. We hear about only a fraction of all loons in Wisconsin that swallow a lead sinker and die quietly on a lake shore. Still, in the time since I started this blog, we have recorded five loon deaths (three just this year) from lead poisoning. I think it is time to see lead poisoning as less of a freak occurrence and more of a regular — and probably important — source of loon mortality. In New Hampshire, half of all recorded loon deaths in a 2017 study were caused by lead toxicosis. Even if we are far better off in Wisconsin, and only, say, 1/4 of all loon adults die from lead poisoning in our state, this seems like an unacceptable number. I say this because we can prevent deaths of loons, eagles, and other wildlife simply by using fishing sinkers made of bismuth, tungsten, steel, or other materials. In short, at a time when the population of loons in northern Wisconsin is already in trouble, why are we still using fishing tackle that kills loons?

John on Lumen Lake sensed something troubling about the loons on around August 13th. He noticed a burst of unusual calls, but he also saw that the chick was still alive, healthy, and being attended by an adult. So he was not sure what to think. As it turned out, the Lumen male was in a struggle for his life on Birch Lake, 2 km away, where he had gone to forage. His miraculous escape and recovery — and his mate’s ability to hold the fort and keep their chick alive during his absence — has become a rare feel-good story to report during a difficult year.

We are able to piece together this story from combined accounts of folks on Lumen Lake, Birch Lake, and our own team member, Lyn, who has generously remained behind in the study area and continued to gather valuable data on chick feeding patterns and survival. The story begins on August 11th, when Lyn made a routine visit to Lumen, found the male alone with the chick, and reported nothing unusual about the duo. Two days later, Mike Henrichs and his three grandkids, Jaden, Jesse, and Jordan, were out fishing on Birch Lake when they noticed an adult loon behaving strangely and found that it was dragging a bobber and fishing line. And here is the crux of the story. Instead of merely reporting the loon in distress to a local DNR office, which lacks the personnel to assist injured wildlife, the Henrichs decided to help it. They could see that the loon was not diving to avoid them, as a loon normally would, so they approached the bird, grabbed hold of the fishing line attached to its leg, and pulled it onto their boat. As their video shows, they then patiently cut the line off the loon’s leg, around which it had become tightly wrapped, dislodged a hook from the loon’s bill, and joyously released it. Everyone had a role. Thirteen-year-old Jaden helped her grandpa hold the bird, locate the line and hook, and release it; 9-year-old Jesse did the camera work, and 7-year-old Jordan endured frequent helpful tips from his brother and kept the boat off shore. The Henrichs were unaware of this loon’s current status and, naturally enough, presumed he was a resident of Birch Lake.

But we knew different. In fact, the entangled loon was not merely a floater, killing time until the fall migration; he was a father with a chick and territory to defend. His sudden entanglement and consequent inability to return to his breeding lake put his mate on Lumen in a bind. She became the sole provider and defender of their seven-week-old chick. Moreover, she was suddenly saddled with the task of fending off efforts of intruders to take over her territory without her mate’s help. We cannot be certain when the Lumen male took someone’s bait on Birch and became entangled in the attached monofilament line, but it was almost certainly sometime on the 11th or 12th, because the bird was quite weak and compromised by the 13th, when the Henrichs freed him. Thus, the female was on her own with her chick for at least two — but perhaps as long as nine — days.

Single parenting, as I have described lately, is no picnic for loons and usually has dire consequences. After the recent debacle on Arrowhead that forced a female there into a prolonged period of single parenting and will likely result in loss of one or both chicks, we were ready for a happier outcome. Still, I was dumbfounded to learn that Lyn had seen the disentangled male back on Lumen — seeming none the worse for wear — on August 20th. Her observation meant that the male had become hopelessly entangled, lost a good deal of strength, been caught and cut loose, and somehow recovered well enough to take off and fly back to his breeding lake within a period of nine days — in time to rescue his mate from her challenging stint of uniparental care. The key to the male’s survival and rapid recovery was no doubt that he was found by a calm, determined family within a few days of his entanglement, when he still had enough residual strength to bounce back and return to his own family.

How could a breeding loon’s desperate brush with death lead to such a heart-warming outcome? Simple. A thoughtful human family took it upon themselves to help a loon in distress. And the loon they rescued took full advantage of their generosity.

My family took a vacation this past week to the East Coast. It was not a typical vacation. We boarded our eastbound flights nervously, wiped our seats obsessively with the comically-small towelettes provided by flight attendants, cinched our masks high over our noses, and glared with disapproval at fellow passengers who failed to do the same. Upon arrival in Boston, my daughter and I waited for three hours in 96-degree heat for a COVID test (both were negative) and then rushed back to the airport to meet my wife and son. Ultimately, though, we all arrived in Vermont for a five-day vacation with family members who could also boast of recent negative tests.

Even without the added stress of coronavirus, I had expected to struggle on this vacation. I loved vacations when I was a child. My parents would throw their four kids into one of those monstrous Chevy station wagons with fake wooden side panels and drive northeast along the interstates from Houston on our annual odyssey to New England. We loved the highways, the motels, the afternoon stops for soda, singing madrigals in the car at night, playing the alphabet game with road signs — and even the adventures we had after occasional tire blowouts. But age has made me hunger for the sound nights of sleep that go with routine and a familiar bed. So when my wife described her plan for a New England holiday — to begin immediately after my daughter and I had buttoned up our canoes and car in the storage box in Rhinelander — I sighed. “Ok”, I said, “that sounds like fun!”.

Despite their many drawbacks, there will always be one big positive about vacations: vacations bring an exciting change of scene. In meeting new people and taking in new sights and smells, you are able to compare — consciously and unconsciously — your vacation spot to what you have seen elsewhere. As a scientist, I appreciate the new connections my brain makes when I move from one location to another.

As it turned out, our visit to Vermont provided an unexpected comparison of two loon populations headed in opposite directions. One of our outings took us kayaking on Kent Pond, near Killington. “Pond” is a misnomer; Kent Pond is a dammed lake that covers 71 acres. According to Eric Hanson, who has been following Vermont loons for almost as long as I have been covering those in northern Wisconsin, the first attempted loon nest on Kent Pond occurred in 2009, and the first chick fledged in 2011. So, Kent Pond — and southern Vermont generally — illustrates how loons can settle in an area, begin to breed, and establish a new population. After I had adjusted to sitting so low in the water and using the quirky two-sided paddle to propel my kayak forward, I joined my daughter and the rest of our party as they sought out the loon pair that inhabited the Pond. We caught up with the tame adults and their two nine-week-old chicks along the northeastern shoreline. The larger chick swam and preened casually and lagged behind the family, while the smaller chick approached and hounded its parents for food unceasingly. Their size and behavior made it clear that these were two strapping chicks. Their wing flaps, moreover, exposed fully adult-sized flight feathers that will soon lift them off of the Pond and permit them to explore other lakes in the area. (I took no photos of the Kent family, but Linda’s photo of a rare two-chick family on her lake is similar.)

After gawking at the two monstrous chicks on Kent Pond for a time, I explored the Pond a bit more and was reminded of one of my study lakes in Wisconsin. Like Kent Pond, Currie Lake is rather round in shape and has two small islands near its center. Like Kent, Currie also hatched two healthy-looking chicks in June 2020. But Currie lost one chick in its first week and the other chick before it reached two weeks of age. In other words, the chick loss this year at Currie exemplifies the current reproductive downturn in the northern Wisconsin population. The two adult-sized chicks at Kent, on the other hand, well represent the Vermont loon population, which continues to grow and expand. (Below is a plot of the size and breeding success of loons in Vermont from the Vermont Center for Ecostudies.)

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I am not a bitter person. I try hard to look without jealousy at those more fortunate than myself and be happy for their situation and not sad about my own. But those two big, fat, sassy chicks at Kent Pond — and the population of which they are a part — showed me a portrait of loon ecology that is becoming distressingly unfamiliar.

I feared in May that 2020 would be a forgettable year for breeding among loons in northern Wisconsin. As many followers of the blog may recall, I wrote numerous posts this spring and summer warning of reproductive struggles of loons in Oneida, Lincoln, and Vilas counties. Before I was even able to visit my study lakes in late May, the die was cast. Black flies, Linda told me in early May, were worse in 2020 than any year during the 28-year study — worse even than in 2014, when about 80% of all first nests were wiped out by the relentless blood-suckers. Indeed, only 3 breeding pairs out of the 109 that we followed this year were able to incubate to hatching a nest that they began in May. The flies were a painful punch to the gut from which the breeding population never recovered.

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Despite the huge setback caused by the flies, most pairs forced to abandon their first nesting attempt renested in June. Many such pairs used promising nest locations on islands, protected boggy shorelines, or marshy mounds formed from emergent vegetation; still others placed their eggs of artificial nesting platforms anchored on lakes by lake residents anxious to boost their efforts. And so, in spite of the challenges, many nesting pairs hatched late chicks. These successful pairs included several on lakes that had not produced chicks in many years, such as Hodstradt, Shepard, and Dorothy. They included a few lakes where entirely new breeding pairs had settled, found good nesting places, and hatched young, like South Two, Silver, and Miller. Finally, one breeding pair — on Baker — performed the most impressive feat of all, raising their own loon chick in 2020 after having reared a mallard duckling to fledging in 2019.

Yet all of these heart-warming breakthroughs combined were not enough to lift the breeding rate this year to respectability. As the graph shows very clearly, 2020 continued the steady decline in the reproductive fortunes of northern Wisconsin loons that began over two decades ago. The decline is marked not only by increased black fly harassment but by increased losses of chicks after hatching — both young and old chicks.  Altogether 9 of our pairs patiently sat on their eggs for 4 long weeks only to lose chicks in their first week of life. An additional 8 pairs reared chicks past the “danger period” of the first two weeks but lost one or both chicks later (and a few more, perhaps, will be lost in the coming weeks). In short, we can no longer breathe a sigh of relief after chicks hatch — or even after they reach 2, 3, or 4 weeks. As a matter of fact, I no longer know at what age we should count chicks as having survived. Mortality of chicks of all ages is much higher now than in the 1990s or early 2000s. Statistically, 31% more young loon chicks (<2 weeks) die now than before, and the death rate of old chicks (>5 weeks) has increased by a staggering 81% in the past 28 years.

After having blithely focused my attention on the territorial behavior of loons for a quarter century, I am now compelled to look at what is causing the sharply higher mortality among chicks and young adults. I feel as though I owe it to the folks who live on the lakes of the Northwoods and imagined that they would always hear the sounds of loon calls echo across the water. And I owe it to the loons themselves.