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

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

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

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

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

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

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

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

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

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

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

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The hatch is underway. 2023 was a miserable year for black flies. But loon pairs that laid eggs in mid-May and kept incubating them despite fly harassment are getting their reward this week. Granted, this reward comes in the form of one or two tiny puffballs that need continual warming, must be protected from a host of predators from above and below, require gentle handling, and can only consume tiny food items offered patiently and gingerly. But such is the reward.

We are especially excited about the two chicks hatched in the past few days on Little Bearskin Lake in the Wisconsin Study Area. Why? Two reasons. First, with an estimated age of 34 years, the mother of these chicks is our oldest study animal. Second, our team happened to capture this female two years ago and discover that she was injured and ailing after getting entangled in fishing line. Our rescue of this ancient female allowed her to rear a chick with her mate in that year and another last year. If she is able to raise the two chicks just hatched with the same male, she will — in our view — have produced four “bonus chicks” above what would have been possible without her disentanglement. The ability to witness several of our study animals resume breeding after cheating death with our help is one of the joys of our work.

“Two chicks on Little Bearskin?”, you say. “I just see one in the photo.” Indeed, Linda Grenzer captured this picture of the single chick that just hatched on Crystal Lake near Tomahawk. I like the way the chick seems baffled at the distance between itself and its nearby parent. (“Why have you left me here?”)

Do not despair if your loons are still on eggs or not nesting. Little Bearskin, Crystal, and a handful of other pairs are among the intrepid few in Wisconsin that survived the barrage of flies undaunted and will hatch this week.

While most of our Wisconsin loon pairs were forced to abandon their first nesting attempts, Minnesota loons in Crow Wing and Cass Counties tended to respond to fly harassment by postponing their first breeding efforts. Hence, the bulk of our Minnesota pairs began incubating during the last few days of May or first week of June. However, a small number of stalwart pairs in Minnesota laid in mid- to late-May and hung in there during the fly weeks. Those pairs — which include Kimball-East, Kimball-West, Little Star, Big Trout-West, Ossie-Boozer’s, and Ossie-Timberlane — should hatch in the next week to ten days, if all goes well.

We are still hopeful for a solid breeding year for both study areas. Fortunately, loons follow the same philosophy that humans do when it comes to setbacks. When you get punched in the mouth, you don’t stay down. You get back up and see to your business.

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The saying “success breeds success” was not coined with loons in mind. But we humans know from experience that an initial success can increase the likelihood of a second one. Indeed, I relearn the value of accumulated experience each spring during the period when I train field observers. With no background in the technique, new observers are utterly astounded when we locate the first nest of the year. After five more nest discoveries, though, they begin to develop a “search image” for nests. It is a thrill to see them learn quickly over a period of a few days to the point where they begin to point out loon nests to me!

Loons are not complete strangers to the benefits of learning. Males often place nests in poor locations when they first attempt to nest on new territories. After a bit of blundering about and some poor decisions, males typically find a nesting spot that results in a successful hatch. Afterwards, they reuse that good spot again and again, enjoying much greater success than during their first attempts. Thus, nesting success following an initial period of failure leads to further nesting success.

The impact of a loon pair’s nesting success on territory defense is another matter. The loon territorial system differs in a crucial respect from those described in other species. In many birds, most notably colonial seabirds, young adults prospect for good breeding sites by looking to see where other adults have produced chicks. When these young seabirds settle to breed, their settlement has little or no negative impact on adults already breeding at the huge colony. Not so in loons. Young adult loons prospecting for territories use chicks they spot on a specific territory as a badge indicating quality of that territory alone. Young prospectors must battle the current residents for ownership of such high-quality territories. That is, chicks seen in one year induce prospectors to return the next seeking to evict the owner of their sex and claim the territory for themselves. So adults that produce chicks experience the joy of parenthood…..but have also placed their future territory ownership in jeopardy.

The mixed blessing brought about by successful chick-rearing is nowhere more obvious than on the Pelican Lake-Mousseau Bay territory in the Minnesota Study Area. Online observers watching via the live nest cam were treated to a lengthy battle between two adult loons a few days ago. While the battle was shocking in its brutality, it was not surprising. We have long known that the successful rearing of chicks leads to a surge in interest in the territory and, hence, the likelihood of territory loss by one or both breeders. After raising two strapping chicks last summer, the male and female of Mousseau Bay must have braced themselves for a litany of territorial intruders and challenges. Indeed, the banded 2022 male apparently lost his position this spring; last year’s marked female is now paired with an unmarked male.

And yet there is hope. Yesterday, the old female laid an egg. She and her new mate both seem anxious to sit on it. If they can weather the blitz of black flies currently dogging their incubation efforts, they stand a good chance of repeating last year’s success.

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I am never prepared for chick loss. As a scientist, I know that the first several weeks of life are fraught with danger for loon chicks. Have they developed normally? Can they thermoregulate properly? Are they able to dodge eagles, muskies, and snapping turtles that can devour them when small? Are their parents aggressive and vigilant enough to keep intruders at bay, which might otherwise kill them with a few well-placed jabs? Is there sufficient food in their natal lake to sustain them and support their rapid growth? And these are merely the natural threats to chick survival.

As hazardous to chicks as natural dangers, or perhaps more so, are threats that humans pose. Sometimes these are direct impacts; humans drive their boats rapidly and often strike chicks, which cannot elude them as deftly as adults. Anglers’ lures and baits, recognized as unnatural and avoided by most adult loons, are sometimes gobbled up uncritically by chicks, which are just learning what they can and cannot eat and must gorge themselves in order to grow. The hooks — and especially lead jigs and sinkers that they ingest at such times — pose a grave risk to the youngsters. A more insidious and dire threat that we have seen recently is the decline in water clarity in northern Wisconsin in the past decade, which makes it difficult for chicks and parents to find food and likely explains much of the reproductive decline we have seen there. (We will soon determine whether water clarity is declining in loon lakes in Minnesota as well.)

Although I am acutely aware of the increasing dangers that loon chicks face, I struggle to adjust to the steady drip drip of chick mortality in Wisconsin and Minnesota. When the Rush-USA Point pair lost their chick, I reasoned, “Well, that territory gets high boat traffic; it is hard to keep a chick alive there.” I justified the loss of the Cross-National Loon Center chick and the two chicks hatched by the Rush-Hen pair in the same way. I was a bit numbed by the time I considered the loss of the two young chicks of the Eagle-East pair.

I find it easier to stomach brood reduction. When broods decrease from two chicks to one, I take solace in the survival of the remaining chick. So it went at Upper Whitefish-Steamboat, Ossie-Island, and Sand this year. Very often brood reduction of this kind comes about because food is limiting; the death of the smaller chick actually gives the larger chick a fighting chance to make it.

What stings the most is loss of chicks that have reached four weeks of age. In the past few days, two chicks that had attained this milestone perished in the Minnesota Study Area. (The NLC is awaiting necropsies on both individuals.) Quick inspection of the Lower Hay-Southeast chick that lost its life and washed ashore earlier this week showed what appeared to be traumatic injury on the back, suggestive of a propeller strike. When you consider that the Lower Hay-SE territory is right next to a major public boat landing, this likely cause makes sense. The second deceased chick, from Clear Lake, was 32% lower in mass than its sibling; thus it was falling far behind in acquiring food from its parents. So this looks like classic brood reduction. Indeed, Kate Marthens, one of our Minnesota field team, reported that this chick was not keeping up with its family on the day that it was found dead, an indication that brood reduction was imminent.

The significant increase in mortality of loon chicks of all ages (i.e. both younger and older than five weeks of age) is a hallmark of the current population decline in Wisconsin. I should be learning to cope with it — preparing myself to face it in Minnesota too, if our growing sample there reveals the same trend. But that is more easily said than done. It still hurts like the devil to lose a chick.

Featured photo — One of our largest chicks in Wisconsin is that on Little Bearskin Lake. It was alive and kicking as of this writing! (Molly Bustos, a Wisconsin intern, holds the bird.)

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It seems ages ago when my team was out on the lakes, finding pairs with chicks, capturing and banding them — then hastily storing our canoes and the Loonmobile for the winter. So much has occurred since early August that those frantic days linger in my brain only as a hazy memory.

But the loons stayed on. While I was vacationing in the East, attending faculty retreats, and lecturing with a mask and fogged glasses so that we could keep classes in-person, loon parents continued to stuff their young with food, chicks matured and learned to fly, and most adults abandoned their territories for the Great Lakes. Even now though, as I brace myself for that peculiar mixture of joy, renewal, and mortification that only Thanksgiving with family can bring, loons remain on many small lakes in the Upper Midwest. Most are juveniles, like the one in Linda Grenzer’s photo, which often postpone migration until the very last second. This strategy probably permits them to maximize their energy reserves for their first long overland journey to Florida.

So hold a good thought for the stragglers. The Brandy Lake chick, which a lake resident told me about in an anxious e-mail today, is among them. Perhaps by the time we are all sitting down for our Thanksgiving meal, that strapping juvenile will have begun winging his way anxiously in a south-south-easterly direction. Though he cannot have a clear picture of his destination, he will cease his migration off of Cedar Key, Panama City, Tampa, Fort Myers, or Apalachicola. For a time he will be that nondescript brownish diving “duck” that some young family from Nebraska watches distractedly while building their sand castle. Let us hope that we see him back up north in a few years — and in more striking attire.

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Although most of our research team is long gone by September, Linda and Kevin Grenzer remain in Wisconsin. At a time of life when most folks widen the dimples in their BarcaLoungers, these two are devoting their time to rescuing injured birds. (Linda, of course, is also one of our field team members and a gifted photographer to boot!)

Linda and Kevin have gotten more proficient at rescue in recent years. Four years ago, they often found themselves hours from home on some false alarm — an eagle that was heat-stressed but recovered; a loon that seemed wounded but was merely preening. These days they insist on seeing photos or getting vivid descriptions of injured birds from experienced observers before setting out to save them.

After Ken and Joanne Lubich sent us the photo at the top of the page, it was clear that a bird was in trouble. The Lubiches keep a close eye on the two loon pairs on eyeglass-shaped Two Sisters Lake. On a routine patrol around the lake on September 13th, they were horrified to see that one of the two strapping chicks on the east lake had a huge muskie lure attached to its left leg and was swimming erratically.

It might seem difficult to find the positive here, but, in fact, this chick was fortunate. The Lubiches keep a close eye on the loons on Two Sisters and have a network of contacts who live on the lake. Thus, the distressed chick was found only a day or so after being hooked. Furthermore, Joanne and Ken know Linda and Kevin and immediately reported the hooked bird to folks who could help it.

Once they made it to Two Sisters yesterday, Linda and Kevin were able to capture the distressed chick, when it ventured close to shore. A quick inspection told them that at least two of the hooks on the lure had punctured the chick’s foot tissue and become infected. They decided to transport the bird to REGI for treatment.

As is evident from the photo below, we had captured and banded this chick. On the night of capture, July 13th, the bird weighed 2460 grams. Yesterday, the chick weighed 2470 grams, which means that it was only 10 grams heavier yesterday than it had been two months before. This tells us that the bird has lost a great deal of weight — perhaps 500 to 600 g — owing to the hooking. Needless to say, loons go downhill quickly when they are prevented from feeding themselves. This bird probably fed little or not at all for six days.

The world is looking brighter for this chick. Multiple hooks were removed from its foot. One hook was too close to a bone to remove and had to be left in the bird. (REGI staff hope that swelling in the foot will push the hook out in time.) If its injured left leg recovers, and it becomes fully mobile again, the bird will be released in a few days back on Two Sisters. Meanwhile, this loon is taking full advantage of the favorable fishing conditions provided in its temporary home!

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The phenomenon is absurd on its face. A loon chick wholly dependent upon its parents for food and protection abruptly abandons them, swims to the shoreline, and sets off through the woods. Hopelessly adapted to an aquatic propulsion because of the posterior attachment of its legs, the chick skootches itself along the ground, resting on its belly at intervals. What could possibly induce a chick to leave its familiar home and loved ones and commence such an awkward and dangerous journey?

If seen only once, a loon chick taking an ill-advised jaunt through the woods would seem like an anomaly — the behavior of a mutant and doomed animal. Indeed, when compared with typical chick behavior, such a reckless journey by a single chick seems to underscore how faithfully most chicks stick with their parents and territory.

But we have witnessed desperate overland treks of chicks many times now, beginning in 1999. On July 15th of that year, I sat on 27-acre Benedict Lake and watched a two-week-old chick get pecked mercilessly by its older sibling. Three days later the abused chick was spotted several hundred yards from the nearest shoreline of Benedict on Witches Lake Road. On July 19th I spotted the youngster again — but on Bug Lake, close to a kilometer’s distance from Benedict. Clearly the youngster had dragged itself out of its home lake, through dense woods, along a country road, and had finally come to rest on a neighboring lake.

As it happened, Bug Lake, though only 21 acres in size, also supported a loon pair. But the Benedict youngster was not well-received there. You see, the loon pair on Bug had also hatched a chick, and that chick was already six weeks old when the tiny refugee from Benedict came calling. As I watched helplessly from the shore, both the male parent on Bug and the giant Bug chick pecked at the Benedict chick, which responded by keeping its head submerged most of the time. Four days later, the Benedict chick was gone.

Followers of the blog may recall another occasion when a chick faced adversity at home, abandoned its natal lake, and bushwhacked its way to a neighboring lake. In this case too, the refugee found a loon pair that had hatched chicks. This time, though, the displaced chick, a six-week-old from Cunard Lake, had better luck. The two chicks already being cared for on the neighboring lake, Hasbrook, were scarcely a month old. Apparently the larger size of the Cunard chick helped it overcome the home-court advantage of its smaller step-siblings. It quickly joined the family and was fed and treated well by both foster parents (see Laura Unfried’s photo at the top of the page.)

A few weeks ago, a singleton chick from Bass Lake set off on a desperate journey from its home lake. No lake in either our Wisconsin or Minnesota study area is more isolated than Bass; it is at least 4 kilometers from the nearest lake inhabited by loons. Indeed, the Bass Lake chick was found wandering along a road and not near any lake. A similar event occurred when the youngest from a rare three-chick brood on Virgin Lake abandoned its home lake in early October 2019 and ended up next to a highway. Sadly, the Bass chick was too emaciated to recover despite being fed by a rehabber. The Virgin chick was fattened up and released on a large lake in the area. Although October is a bad time for a chick to be starving and try to regain its health — and migrate — there is a chance that the Virgin chick survived and made the flight southwards.

How are we to understand the decisions of chicks — ranging from two to thirteen weeks of age — to jump ship and head out across the land? I think the pattern has become clear from the four examples described here and several other cases reported by rehabbers like REGI. Food shortages on small lakes have dire consequences for loon families. Loon chicks are entirely dependent upon food in their natal lake, until they are able to fly off of it. So if food runs short (or an aggressive older sibling prevents them from getting any), chicks can either leave the lake or starve. Striking out across the land is a longshot bid by a defenseless chick at any age. It is far more likely to be eaten by a coyote or a fisher — or simply die of starvation — than to find a foster family willing to take it in. But when staying at home means certain death, even a longshot journey becomes an acceptable option.

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Yes, it has come to this. Chick production of breeding pairs in northern Wisconsin has declined steadily during the past quarter-century. Black fly outbreaks have made hatching success even worse in the past five years. So we are searching desperately for a positive outcome that we can greet with a sigh of relief. And we have one: breeding success has ticked slightly upwards in 2021.

I wish I could report that breeding success has rebounded with a vengeance. After a dreadful 2020, I felt that a strong rebound might be in order. But the recovery has been modest. Looking at the numbers, only three breeding pairs in our study area had chicks as of this date in 2020. That laughably low number resulted from 97% abandonment rate of May 2020 nesting attempts owing to black flies. Meanwhile 59 pairs were incubating eggs on this date in 2020. As of August of last year, 36 pairs were rearing chicks. This amounts to about 33% chick production in 2020 (36 of 110 breeding pairs). At present, we have 24 pairs in Wisconsin raising chicks and 41 other pairs still sitting on eggs. If we use the 2020 nesting outcomes to project 2021 success, we should end up this year with roughly 46 of 110 pairs with chicks in northern Wisconsin. A 42% breeding success rate is nothing to crow about. But since I am a positive person, I will choose to focus instead on the 28% increase in chick production between last and this year!

What about Minnesota? We have only just arrived in Minnesota and have no data from 2020. So we are not able to provide a very calibrated picture of breeding success in the Crosslake area, where we are located. Furthermore, Crow Wing County, where we work, is running about a week behind Wisconsin, so our data are even more preliminary in Minnesota than in Wisconsin. Still, we can already say that 2021 was a light black fly year in north-central Minnesota, as it was in northern Wisconsin. And that is a good thing. Out of 104 territorial pairs we are currently following in the Crosslake area, Jordana and Katy reported a few days ago that 13 have chicks and 42 are on nests. We estimate that the total pairs with chicks will number about 40, by the time August rolls around. But we are still scouting many of our Minnesota lakes, so that number could grow to 50.

Scouting new lakes is a tricky business, by the way. Going onto a new lake with no information on previous loon usage or breeding success forces you to read the behavior of loons on the lake to infer if those you see are: 1) an established pair that has is not currently incubating eggs, 2) a pair that hangs out together but never breeds, 3) an unpaired young floater, or 4) the “off-nest” member of a pair, whose mate is on a nest on the lake. Katy and Jordana’s daily sleuthing has been effective so far. But sometimes you misread the signs, which, in fact, can be thrilling. No doubt a few lakes where K and J found no loon or only a skittish loner on their first visit will offer a view like that in Linda’s photo on their second.

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I have spent my entire academic career making logical deductions about animal behavior. In the early 1990s, I was part of a team of ecologists at Purdue University studying the peculiar cooperative breeding behavior of stripe-backed wrens in central Venezuela. This species could hardly be more different from the common loon. Stripe-backed wrens live in social groups of up to 10 adults, headed by a dominant male and a dominant female, which, we thought, were the only group members to breed. The other group members comprised adult offspring of the dominant male and female that had remained at home as breeding helpers instead of dispersing to breed on their own. When DNA fingerprinting revealed that subordinate males in some groups sired young through matings with dominant females, it surprised us. Seeking to follow up on the striking genetic pattern, I reasoned that the behavior of the wrens should reflect the mixed paternity of the offspring. Specifically, I predicted that: 1) subordinate males were probably actively pursuing matings with dominant females, 2) dominant females were likely seeking out matings with subordinate males, and 3) dominant males were probably not happy about these liaisons and might be expected to attack subordinate males in an effort to deter their amorous proclivities.

My predictions were not rocket science, of course. Though we had no inkling from past behavioral observations that anything but strict monogamy was occurring in wren groups, it stood to reason that we had missed some social behavior that might have clued us in to the mixed parentage pattern we discovered in the lab. Indeed, my behavioral study of the wrens during April and May of 1990 and 1991 revealed all three predicted behavior patterns. During the “fertile period” of the dominant female, the dominant male and various male helpers vied to remain in close proximity and copulate with her when she was receptive. Aggression among competing males was fierce. Dominant females, it seemed, encouraged competition among males wishing to mate by openly advertising their readiness to mate. However, this suite of aggressive and mating behaviors only occurred in “stepmother groups” — those in which a past dominant female that was the mother of all the male helpers had died and been replaced by a “stepmother” from an unrelated outside group. In fact, the death of a dominant female was a crucial event in a wren group, because it turned a staid, monogamous breeding system into all-out warfare between her husband and sons to mate with her successor. Sorry…….I had not meant to go on about my old wren work, but those interested can check out this paper.

Here is my point. As I said, one could hardly hope to find two species more different than common loons and stripe-backed wrens. From the standpoint of a behavioral ecologist, the wrens would seem to offer a cornucopia of research opportunities: helping behavior, living in social groups, deferred breeding by helpers, mating competition. Many questions about the complex wren breeding system remain unanswered. (It does not help that one must travel to an unstable country that generally dislikes Americans and tolerate dreadful living conditions on a ranch overrun by aggressive feral pigs.) But one lesson I have learned is that close scrutiny of any animal’s behavior reveals unsuspected richness and complexity.

The monogamous mating system of loons would seem to offer little to the behavioral ecologist. But the peculiar — possibly unique — system by which young adults seek to learn about breeding territories and established breeders seek to deter their efforts is a gold mine. Consider late-summer social gatherings. The three sets of attendees at these gatherings have recently come into sharp focus, as I describe in a new page I have added to the website. Now that we understand which loons are attending social gatherings and why, we can generate specific predictions about how different attendees should behave that provides a framework for future research.

If members of a territorial pair are trying to safeguard their territorial tenure from floaters, which try to find chicks and use chicks as a badge of quality to target pair members for eviction, pair members should take pains to hide their chicks from floaters during social gatherings like the one shown below.

Thus, we can predict that parents of chicks should lead floaters and other intruders at social gatherings away from the part of the lake where their chicks are hiding and generally discourage exploration of their breeding lake. Furthermore, parents with chicks should behave aggressively towards intruders in cases where a “flotilla” of adult loons approaches the place where the chicks are stowed. How should breeding pairs behave that have failed to produce chicks? They should encourage intruders to explore all parts of their territory, because they want floaters to conclude that there are no chicks present and that the territory is not worth fighting for. For their part, floaters should always try to move about the territory as widely as possible in an effort to spot any chicks present. Finally, how should intruding neighbors behave? Like floaters, intruding neighbors should wander widely in another pair’s territory and induce other intruders to do likewise, in order to maximize the likelihood that floaters spot the chicks of the home pair and return the next year to evict them. In cases where one or two loons appear to “lead” the flotilla about the territory, such as the two left-hand adults in the video, the leaders should tend be floaters or intruding neighbors, not members of the home pair (unless the home pair is without chicks).

Naturally, it will take a lot of work by observers skilled at identifying loons from color bands to test these fine-grained, specific predictions about loon behavior during social gatherings. But now that our long-term probing of loon social behavior has exposed a richly textured system of social information and deception, I relish the challenge.