I have put off writing those words for some weeks now. The patterns in my data were clear; every measure of breeding success was pointing downwards. If you have been following the blog, you might recall that number of chicks per pair has fallen sharply since I began studying loons in 1993. Although I had not reported it yet, loss of chicks after hatching has also increased significantly since I began my work. That is, many pairs hatch two young but lose one or both of them nowadays. Furthermore, even chicks that survive to five weeks of age are now in poorer condition (as measured by body mass) than in 1998 or 2006 or 2013. In short, breeding pairs in northern Wisconsin now raise fewer and less robust chicks than they did 25 years ago.

A combination of scientific caution and denial caused me to delay describing the implication of these trends — and others that I have detected more recently. As a scientist, I am used to finding one pattern, drawing a tentative conclusion based on that single finding, and then being proven wrong by the next finding. Having had an initial conclusion reversed many times during my career, I was unwilling to sound the alarm without a stronger, more consistent set of findings. But the data I now have are consistent and come from multiple independent analyses. Furthermore, the data are fundamentally simple. My conclusions are not derived from complex models based on measurements of invisible particles detected by finicky high-tech devices. We are just counting and weighing loons here!

Still, you might wonder why my earlier caution has turned so suddenly to alarm. Let me explain. I followed a simple line of reasoning. If loon pairs are producing fewer and weaker chicks, then fewer chicks must be able to migrate to the wintering ground. And if fewer juveniles make it to Florida, then fewer should survive long enough to return to northern Wisconsin (which happens at 2 to 4 years of age) and look for a breeding territory of their own. So, declining chick production should result in a reduced population of nonbreeders (or floaters) in our study area, which are young adults looking to settle on their first territory with a mate. Since we mark chicks and obsessively reobserve them as young adults, we can test the idea that lower chick production has resulted in fewer floaters. The results are stark. After one adjusts for number of observer-hours spent looking for floaters each year, a dramatic pattern

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emerges. The population of floaters has plummeted. Look at the scale of the graph carefully. This is not a small decline. Between 1998 and 2006 the number of floaters seen per observer hour fell from 0.020 to about 0.010. From 2006 to 2015, that number has fallen still farther — to about 0.006. In other words, we have seen roughly 1/3 as many floaters from the 2015 year class (which are 4 years old now) as we saw from the 1998 year class. In terms of percentages, we reobserved about 45% of all chicks banded in 1998 and 1999 much later as adults; we see only about 14% of banded chicks as adults these days.

So what? Floaters are nonbreeders. They contribute no offspring to the population. Do they really matter? There are not even enough territories to hold them. They are surplus individuals, in a sense. You might view the presence of any floaters at all as a positive sign that the population is bursting at the seams. Yes….but floaters are also the future. That is, floaters are loons not yet old enough to claim territories but waiting to fill in for dead breeders (or evict them forcefully). Without floaters, a breeding population cannot sustain itself, because, inevitably, breeders die and must be replaced.

Even now that I have a set of strongly suggestive patterns, I cannot be absolutely certain that loons are in trouble in Wisconsin. Perhaps the steep decline in floater survival simply means that the weak floaters now die off long before settlement, leaving the strong ones to replace dead breeders. Perhaps something very odd is happening in the north-central part of the state (more intense human recreational activity?) that is not happening elsewhere. So, let’s keep fingers crossed that this is a fluke of some kind. But I am convinced that we are seeing a worrisome pattern that is unlikely to be confined to my study area.

What does the future look like, if the floater population truly is declining markedly, as I suggest? Despite the strength of the pattern, the short-term effects might be subtle, because loons are long-lived. Imagine that families in your town or city suddenly began to have only 1/2 or 1/3 as many children as in years past. When would you notice a marked change in the community? You might — if you were very sharp — notice fewer large families at local playgrounds. Sometime later, you might notice the closing of a school here or there. But decades would pass before you would discern a loss of occupied homes in your neighborhood (presuming that kids in your town grow up to inhabit local homes).

So it will be with loons. On some lakes, the death of a pair member — especially a male, because males are in short supply — will leave a vacancy that is not filled by a floater. Some lakes that always supported a breeding pair will lose that pair and instead only see loons that come and go to forage. Large lakes with six perennial breeding pairs will, over time, see some territories “wink out”, leaving only three or four. In a few decades perhaps, even those territories will vanish. If I am correct, and unless this long-term pattern in the survival of young loons reverses itself, loons will ultimately disappear altogether from northern Wisconsin.

The Audubon report put me on notice. Loons are not immune from climate change. While I have wondered at times whether their aquatic habitat might somehow buffer them from the warming of the Earth and increased moisture in the atmosphere, this was a false musing. Recent changes in temperature and precipitation have myriad and complex effects on lakes and their inhabitants. Loons will have to confront the changing conditions just like all other organisms must.

I wondered whether my long-term data on loons might show climate-induced changes. I am not a climate scientist — nor even a hard-core ecologist who might routinely measure fish populations, water temperatures, or lake chemistry. But we do weigh all loons that we capture and band. Perhaps masses of adult loons or chicks have fluctuated in response to the changing climate.

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My findings are quite striking. Chicks have decreased in mass consistently since my team began capturing and marking loons. This finding alone is worthy of concern, but it is not the only one. Breeding males (see below) too show a decline in mass during our study. Breeding females, on the other hand, show no steady loss in mass.

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What are we to make of these patterns? Are populations of small fish down in the past few decades such that chicks and their male parents struggle to put on or maintain body mass? Or are lakes changing in ways (e.g. clarity) that might make fish more difficult to catch? Whatever the cause of these decreases in mass, why are female loons not affected similarly? These questions must remain unanswered for the time being. In fact, these results are so new that I must run some more double-checks before I fully trust them. Even if they are real effects, as it appears, it is much too early to attribute them to global warming. My worrying self, though, fears that these significant declines in body condition might be the leading edge of a changing climate’s impacts on Wisconsin loons.

On its face, it seems absurd. Why would loons ever communicate with eagles? Apart from raccoons, bald eagles pose a greater threat to loons than any other species. Eagles are opportunistic feeders, always looking for an easy meal. And they are large and well-armed enough to seize almost anything edible they find. Nesting loons provide a tempting stationary target for eagle attack. We have had two eagle kills of nesting loons during our study. The eggs themselves are vulnerable to eagles, because they do not flee and provide a nourishing snack. Loon chicks, whose diving skills are more limited than adults’, also draw unwanted attention from eagles. According to our own observations and those of others on our study lakes, eagles are a major cause of mortality among loon chicks older than two weeks. No doubt this explains why chicks learn to track the movements of nearby eagles obsessively, like the three Bass Lake chicks in Linda Grenzer’s photo.

Why would loons, which seem to spend most of their waking hours scanning the skies for eagles, ever speak to them? Could it ever be profitable to speak to your arch enemy? According to a number of studies by behavioral ecologists, it could, providing the information you pass along to your enemy increases your likelihood of surviving.

Deer and antelope engage in a behavior termed stotting in the presence of predators. Stotting means jumping upwards (often while flashing the tail upwards) in a way that makes the animal more conspicuous to its predator. But data collection and analysis on the occurrence and timing of stotting by gazelles has shown that they chiefly practice this behavior when they spot the predator at a distance and can easily outrun it. This and subsequent research suggests that prey often signal to predators to inform them of the unprofitability of an attack. That is, a prey species is saying to its predator, “I see you and am faster than you; save us both a lot of time and energy by looking elsewhere for food.” In fact, honest signals between prey and predators are not uncommon in nature. Many animals have evolved bright warning coloration to signal to potential predators that they are poisonous or dangerous to the predator in some other way that makes attacking them a bad idea. Colorful prey are, in effect, doing predators a favor by informing them that they should not attack! (Again, though, the prey are acting in their own best interests, not the predator’s.)

Could the mournful sounding wail that we often hear from loons be a signal to eagles that they have been spotted and that an attack would be fruitless?  If so, wails should: 1) occur often when eagles are passing overhead, but only when they are at a safe distance, and 2) be emitted by loons regardless of the presence or absence of other loons (like mates and chicks). The second prediction is crucial; if loons give wails to eagles only in the presence of their mates and chicks, it would seem as though they are simply warning their family about the eagle and not talking to the eagle itself. Our data clearly show that the wail is a long-distance signal given by loons when eagles are overhead. And loons wail to eagles whether they are alone or with mates and offspring. So loons certainly look as though they are speaking to eagles with their wails.

Strange to think that telling your arch-enemy anything could ever be a good idea!

I will admit it: I am flabbergasted. When the Bass Lake pair hatched three chicks in the first week of July, I never gave them a chance. I suppose my pessimism was, in part, an attempt to protect myself from further disappointment. This year, as I have mentioned, has been a forgettable year in our study area. The dust has not yet settled completely, but 2019 will certainly go down as the worst year for chick productivity since I began the study in 1993. And we have had some dreadful breeding years!

The Bass Lake Miracle — hatching and rearing of three vigorous chicks on a tiny lake — is so far a welcome exception to the dreary pattern. As I noted in my previous post, however, the Bass Lake pair are fighting more than the negative tide of 2019. Lakes that you could throw a baseball across — well, lakes that Trevor Bauer could throw a baseball across — generally do not contain enough food to allow two chicks to reach fledging size, let alone three. Fawn Lake is a case in point. Slightly larger than Bass, Fawn hatched two chicks, which weighed 2.1 and 1.2 kilograms at capture ten days ago. So the smaller chick is just over half the weight of its sibling, and its survival prospects appear grim. Moreover, Evelyn reported that the beta chick was begging fruitlessly for feedings from the male today, while its fat and sassy sibling rested nearby. Such is the normal state of affairs for families that try to raise more than one chick on small lakes.

But don’t tell all of this to the over-sized Bass Lake family. As Linda’s recent photo shows, the trio of chicks there are beating the odds so far. During my visit to the lake today, the three-week-old chicks swam along in a tight group, tracking their foraging parents and getting fed constantly. The food items brought up by the parents were not tiny minnows and leeches, such as one often sees on smaller, food-stressed lakes, but crappies and yellow perch large enough that the chicks had to work a bit to swallow them. There was no desperate begging, no pecking of the small chick by its larger siblings. Most important, the size disparity among the chicks, quite evident a week ago, is less so now, which suggests that all chicks are receiving ample feedings.

I retain some healthy pessimism about the loon family on Bass. I have seen too many starved chicks on small lakes to feel otherwise. But if a pair of loons can adopt a mallard duckling, raise the duckling on fish they catch and feed to it, and teach it to dive as they do, I suppose anything is possible.

The loon pair and mallard duckling remain a close-knit family, if a non-traditional one. This fact became clear on Linda’s recent visit to Long Lake, as the pair remained fiercely protective of their charge (as her photo shows), and the male permitted it to preen while standing on his back. But Linda’s observations also suggested that the duckling is not helping its foster parents’ in their efforts to safeguard their territory ownership.

Let me provide some context. During July and August, loons that do not have territories  look hard for them. Why? Well, because (with apologies to Jane Austen), “….it is a truth universally acknowledged that a single loon in good physical condition, must be in want of a territory.” Indeed, single loons search ceaselessly, and at times desperately, for territories and mates. They do not search blindly but instead heed a signal. The presence of chicks with a breeding loon pair is a shining beacon to unpaired loons that announces, “This is a good breeding territory; remember this lake, return to it next year, and claim it for your own!”

In order to counter the prying eyes and evil intentions of such nonbreeders, loon pairs play hide-and-seek with their chicks. This is not the kind of light-hearted hide-and-seek that we humans play with our offspring. Instead, loon pairs with chicks play a high‑stakes hide-and-seek game to keep nonbreeding loons from spotting their young.  And if pairs (or their young) play the game poorly, they place their future territory ownership at risk.

Hiding of loon chicks by parents often seems a difficult task. Loon chicks are chocolate brown in color and can hide near shore among rocks and logs — if they wish to do so. Nonbreeders, for their part, do not call ahead to warn of their visits. Instead, nonbreeders appear suddenly over a lake, flying at 70 miles an hour, and scan the lake’s surface for loon chicks. Often they land in the lake as well. Under these circumstances, it is a daunting task to keep chicks out of sight. Yet, if pairs with chicks are fortunate enough to spot flying intruders early and to be in a part of a lake from which their chicks can easily swim to shore, they sometimes hide their chicks successfully by means of an odd “dive and scatter” strategy.

Hiding of a fostered duckling from snooping intruders has turned out to be an even greater challenge, Linda reports. While keeping a fostered duckling well fed is easy, preventing intruders from spotting the duckling is comically difficult. Picture the scene from a few days ago. An intruder suddenly appeared overhead, emerging out of the early morning fog while the loon pair and duckling were resting. Both adults immediately dove and swam underwater towards the center of the lake to engage the intruder. Instead of diving itself and racing underwater to hide near shore, as a loon chick would have, the duckling freaked. When it spotted its foster parents far away and next to nonbreeders that had landed, the duckling raced towards middle of the lake, while peeping loudly, making itself very obvious. Needless to say, efforts by the loon parents to hide their youngster were at an end.

I know what you are thinking — the loon pair lost nothing from the conspicuous behavior of the duckling. The intruder might have been confused by the duckling’s presence, but it probably would not have confused the duckling with a loon chick, taken it as a sign of breeding success, and planned to challenge the pair for territory ownership next year. That is probably true, unless, of course, nonbreeders cue in not only on loon chicks themselves but also on protective and aggressive behavior exhibited by loon parents. Let’s hope the duckling’s misbehavior had no long-term impacts. It would be a shame if the loon pair suffered doubly — by rearing a youngster of the wrong species and losing their territory the following year.

This is a frantic time of year for wildlife and wildlife rehabbers. Why? Because while you are ditching Weird Aunt Beatrice at your family reunion, loon pairs and their chicks must dodge your crazy nephew Lucas on his Jetski. Needless to say, loons have considerably more on the line.

The tranquility of May did not prepare the Tomahawk-Kemp pair — or me — for the life and death struggle they would face in July. On May 11th I ran across the super tame male and female from Tomahawk-Kemp when they were preparing to nest in the long channel between Minocqua and Tomahawk. On that visit, they seemed almost to welcome my presence, and it was a simple matter to scribble down all of their colored leg bands as they rested and made short dives near my canoe. I experienced one of those moments when you are alone with nature and feel a sudden, ineffable connection with a wild animal. I wondered: “Does the male remember me from 17 years ago, when I first encountered him as a settler on South Two Lake?”

The Tomahawk-Kemp pair’s recent experiences with humans have been considerably less pleasant than those in May. We do not know the whole story, but on about June 17th, the pair hatched two chicks. (Judith Bloom, whose June 20th photo appears above, helped us narrow the dates with her routine checks.) Having survived black flies, raccoons, eagles, and curious humans to hatch both eggs, the Kemp pair headed out into the main body of Tomahawk to locate small fish suitable for their ravenous youngsters. There they began the daunting task of diving to catch food for the chicks, while at the same time helping the tiny fuzzballs steer clear of boat traffic. Most boaters adhere to local ordinances with respect to speed, distance from shore, and respect for wildlife; some do not. We suspect that a boater in the latter category ran down – either purposely or not – the Kemp hatchlings on the 1st or 2nd of July. The parents were unscathed; adult loons can dive rapidly and deeply, and those living on Lake Tomahawk have ample experience avoiding motorboats. Young chicks, however, have neither the diving capacity nor the familiarity with speeding watercraft to help them escape collisions.

Both chicks were hit by the boat. Linda Grenzer snapped the photo below of the less severely injured chick; it showed a healed wound towards the tail end, near the base of the left leg.

LMG 26251 Lake Tomahawk Kemp Injured Chick

The second chick looked better externally but had internal damage from the boat strike — a ruptured air sac — which prevented it from floating upright in the water. (Bird’s air sacs are thin membranes that connect to the lungs and are part of the respiratory system.)  So Linda, Elaina, and Kevin decided to catch this listing chick and take it to REGI for treatment. Fortunately, REGI repaired the damage, fed the chick well, and prepared it for successful release three days later. As you can see from Linda’s photos at the release, both pair members quickly accepted their missing youngster.

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On the other hand, its sibling had apparently enjoyed being an only and had mixed feelings about the reunion!

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According to recent reports, all is now well with all four members of the Kemp family. Life will continue to be a wild ride, because boat traffic will not wane for several more weeks, and the siblings will no doubt bicker over food from time to time. Since chicks rapidly improve their diving skills, though, we can hope that these two have had their last close encounter with fast-moving watercraft.

 

 

At first glance, a mallard duckling raised by loons would seem to be in a pickle. When your parents dive and you do not, you spend many anxious moments waiting on the surface. Furthermore, when you instinctively prefer to spend time in the shallows, and your folks prefer open water, you must tolerate their habitat preference as best you can, while nervously peering under water a bit more than usual.

These minor sources of stress seem tolerable for the Long Lake loon-duckling. As it turns out, there are benefits to having two parents assiduously stuffing food into you instead of one parent merely leading you to foraging areas.

You see, when we first observed that a loon pair had adopted a duckling, we were unsure how the duckling might be getting food. We could see that the duckling was healthy and strong — that it continued to grow and thrive. How, we wondered, was a dabbling duck that evolved to pluck and consume small, squishy invertebrates from the shallows surviving with two parents determined to feed it long, rigid, scaly items captured from the deep?

As we can see from Elaina’s stunning photos, the duckling’s solution has been to accept the proffered scaly items — though only small ones that do not pose a swallowing hazard — and to supplement this steady vertebrate diet with bits of animal and plant material gathered on the fly. To look at the bird, this duel feeding mode provides a favorable balance. The adoptee has matured rapidly from a tiny fuzzball into a strapping individual fast approaching adult (duck) size.

While it is physically healthy, the duckling’s mental state is less clear. This bird is a living, breathing test of nature vs. nurture. If the duckling behaves as genes dictate, it will soon join others of its species in huge foraging groups that congregate on lakes at this time of year. But it is thoroughly imprinted on its loon parents, not on mallards. If it has lived too long as a loon chick, it might attempt to associate with that species. Even in this worst case scenario, all is not lost, I think. Full grown mallards, even those that evince inappropriate affection for loons, know that they must bolt when a loon comes stalking them.

I am still deciding how to feel about recent events. On the one hand, one of our marked females lost her mate and territory, beached herself on a lake shoreline, tolerated a lengthy car ride, survived a difficult surgery, and now faces an uncertain path to recovery. On the other hand, a crew from the Loon Project and veterinary staff from Raptor Education Group, Inc. rescued this bird from near death, transported her safely to the REGI facility, expended countless hours conducting major surgery, and is diligently nursing her back to health. These heroic efforts – especially those of the REGI staff and veterinarians — have transformed certain death into the prospect of full recovery.

As I struggle to process this troubling series of recent events, one image lingers. It is the x-ray below (provided by REGI) of the female’s gut seemingly stuffed with fishing tackle.

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Foremost among the questions swirling around my brain is this one: Is ingestion of fishing tackle a common occurrence? That is, do many adult loons in northern Wisconsin have to contend with fishing gear they have swallowed while foraging?

Our understanding of lead poisoning, scrutiny of our field notes, and inspection of the fishing gear recovered from the female’s gut (in the photo from REGI) help in answering this question. Lead is a potent toxin in birds and mammals, causing severe impacts to nervous and digestive systems. Lead toxicosis, moreover, occurs shortly after loons ingest lead — a day or a few days later — not weeks or months after ingestion. Linda Grenzer reported the Mable female intruding on her lake on 20 June. So the female was flying normally three days before she became utterly helpless on Mable (23 June). Furthermore, the fishing tackle in the photo seems to represent that found on the end of one person’s line. So the Mable female apparently swallowed someone’s fishing line on about the 20th or 21st of June and quickly began to deteriorate. Viewed from a population perspective, this is good news, because it suggests that loons in our study area do not ingest lead sinkers very often. If they did, we would face the ghastly prospect of helpless, neurologically-impaired loons constantly casting themselves ashore on our lakes.

Having concluded that the plight of the Lake Mable female is the exception, not the rule, I have begun to breathe more easily. Loons face considerable hurdles in coping with fishing tackle in northern Wisconsin, but lead poisoning — as far as we can tell — seems to be somewhat less of a threat in the Upper Midwest than it is in other populations. So I will end this post on that cheerful note and with Linda’s cheerful photo of the 2019 Loon Project team, which has worked tirelessly to watch over our study population this summer.

2019 loon team at REGI w MAble female

“Wow, loon chicks and ducklings sure look alike!” Evelyn remarked upon returning from Long Lake two weeks ago. Elaina, a veteran assistant who has seen a lot of both, thought this statement a bit odd, but was not terribly surprised. The chicks of loons do look somewhat like ducklings. Both are duck-shaped and downy, quite unlike adults of their respective species. And after all, Evelyn had never laid eyes on a loon chick before.

Ten days passed, and it was Elaina‘s turn to visit Long Lake. She was stunned to find the female slowly swimming about with a young mallard duckling on its back, and she took these cool photos to document her observations. The female, Elaina noted, acted as loon parents always do: she nervously guarded her small passenger, scanning the skies for bald eagles and peering underneath the water at intervals for large snapping turtles and muskies. The nearby male too behaved normally. Like his mate, he was vigilant, but he also caught tiny fish, carried them to the duckling on his mate’s back, and attempted to feed it, just as he had his own chick last year. His efforts were in vain; the duckling refused all food.

Many questions leap to mind here. First, how on earth did a loon pair meet up with a single mallard duckling? Second, why on earth would they adopt the duckling rather than raising their own chick or chicks? Third, why does the duckling participate in this charade? Fourth, will loons, which provide their chicks with a large fraction of their food, be able to rear a mallard duckling, which normally finds all of its own (very different) food?

The first question is the easiest. Loons and mallards are both common on our study lakes. They encounter each other all the time. But the usual result of such encounters is starkly different from what Evelyn and Elaina observed. For their part, mallard ducklings swim about with their many siblings in a large, tight, comical flotilla behind their mother. Loons often stalk these flotillas, causing the mallard female to rush her offspring to the nearest shoreline. Loons occasionally attack and kill ducklings, but do not eat them (to our knowledge). The usual nature of loon and mallard interactions, in other words, is a far cry from what Evelyn and Elaina observed.

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The second question — what the loons are doing adopting a duckling – is the most vexing. Yet we have insights that permit us to reconstruct some parts of the story. The shape, size, and number of eggshell fragments in a loon nest tells us the fate of a nesting attempt. When I visited Long on 13 May, the pair had just started nesting, so we expected a hatch on 10 or 11 June. Indeed, Evelyn noted many small fragments on Long on June 14th—- a clear sign of a successful hatch. So we know that the Long pair did hatch an egg —- a loon egg — about two weeks ago. Loon pairs provide extensive parental care for their young, of course, and are hormonally primed to do so. Without question, then, the Long pair had high levels of prolactin in their blood in mid-June, as they began to care for their own chick. The rest of what occurred to bring about this most unlikely association is open to speculation. Perhaps a tiny duckling, the last to hatch in its brood, was left behind by its mother and siblings. Maybe the duckling became separated from its mother and siblings following an eagle attack. In any event, the tiny waif was likely discovered by the loon pair just after they had lost their chick and were predisposed to find and care for anything that even remotely resembled a newly-hatched loon.

Classical studies of animal behavior help us answer the question of how the duckling would accept loons as its parents. Ducks (like chickens and many other precocial birds) have a well-known capacity to imprint on the first large, moving, animal-like object they encounter after hatching. This instinct makes sense, because that object is almost always their mother or father. Imprinting helps them fixate and remain near their protector at all times. But a duckling hatching after its sibs had left would not have had a chance to imprint on any object. So it is conceivable that such a duckling might see and latch onto a loon pair. If ducklings accept humans as parents, they should easily accept loons.

Can a loon pair provide enough nourishment and feeding opportunities to allow a duckling to survive to fledging? We shall see. Loons have adopted ducklings before. A published study from the late 70s reported adoption of five eider ducklings by a pair of Arctic loons, and I reported a few years back on a pair of common loons in British Columbia that adopted a common goldeneye duckling. In both cases, the ducklings were known to have survived for many weeks in the care of their foster parents. But a mallard is a dabbling duck, not a diving duck, like an eider and a goldeneye. Mallard ducklings normally feed themselves on a variety of invertebrates and plant matter found on shorelines and in shallow water — not fishes provided by a parent bird. Despite the seeming disconnect between loons and mallards in diet and mode of feeding, Elaina’s photos show an alert, healthy-looking young mallard. Since we know the loons have been parenting the duckling for at least ten days, we must conclude that the youngster is receiving substantial nourishment by some means. So perhaps loons can keep a mallard duckling alive.

In short, we know bits and pieces of the story of how a pair of loons came to care for a mallard duckling. Much regarding this series of unlikely events remains shrouded in mystery. Even in our considerable ignorance, though, it is impossible not to marvel at this charming spectacle.