Since we band hundreds of loon pairs, we get used to losing pair members here and there. The female on Sunday Lake, newly-banded in 2020, did not return in 2021. Likewise there is a new male on Clear2-Seven Islands, a new female on Towanda, a new male on Harrison Flowage. Some losses of old pair members are gut-shots. The absence of both pair members at Arrowhead reminds us of the tragic close to that lake’s 2020 breeding season. The Baker male’s disappearance is bittersweet; it brings back the recollection of his having reared a mallard duckling in 2019 with his mate. But after many years of watching breeders vanish, I now greet most such losses with only a sigh.

A bit more unsettling than mere disappearances of single birds — and far more interesting to a behavioral ecologist — are cases where breeder loss on one lake has ripple effects on lakes nearby. Since such domino effects seem to occur shortly after ice-out, when our lake coverage is spotty, we must usually guess at what transpired. In 1998 for example, the McGrath and North Two males, which defended adjacent lakes, seemed to switch places for no obvious reason. We inferred at the time that the huge North Two male flew over and evicted the smaller McGrath male, while the McGrath male assuaged his loss by settling on North Two, which his conqueror had just vacated. But we will never know for certain. A similar mystery occurred last year on Upper and Lower Kaubashine, whose males swapped lakes early in the year, before we were there to see how it happened. Again, we surmise that one male evicted the other, and the loser merely filled the victor’s breeding slot.

This year, we had enough observers present at critical moments to read the ripples more precisely. Following the eviction of his mate on May 3rd (Linda’s photo shows that evicted female), the Upper Kaubashine male — yes, the same male that had swapped territories in 2020 — must have decided that his breeding prospects were dim on Upper Kaubashine. So he looked nearby for an alternative. He found it on Silver, a small lake with an artificial nesting platform and a resident, Pat, who misses nothing. On May 9th, the Upper Kaubashine male intruded onto Silver, where the pair was incubating eggs, beat the resident male severely, and forced him to take refuge in a swampy area. The defeated male has not been seen since.

There is a ray of sunshine to share. The Upper Kaubashine male had no interest in sitting on the eggs of his predecessor at Silver, so the lake’s first nest was abandoned. But the usurper wasted little time renesting with the old female at the opposite end of the lake. Boosted in part by the earliness of ice-out this year, the Upper Kaubashine male might actually survive the loss of his mate and a vicious territorial battle of his own and still hatch chicks in June!

The events of the past few weeks on Upper Kaubashine and Silver reveal that chaos on one lake can spill over to others nearby. So if loons are capable of hope, they should hope for peace and tranquility for their neighbors as well as themselves.

I was on pins and needles. Gabby had moved steadily northward and westward in her censusing of our study lakes. She started in Rhinelander. This from her datasheet Thursday:

Mildred:

  1. O/Ts, W/S (O & left leg double confirmed)
  2. Unb, Unb (both legs double confirmed)

Maud:

  1. P/S, G/G (P & left leg double confirmed)
  2. Unb, Unb (both legs double confirmed)

Coon:

  1. Ronly, Bs/S (both legs double confirmed)
  2. Unb, Unb (almost positive it’s unbanded – never saw its legs out of water, but had many chances to see bands in good light underwater if there were any present)
  3. Intruder = Y/Y, Bs/S (both legs double confirmed). Interacted with pair for 10 minutes.

Ole:
No loons

Soo:

  1. M/S, W/B (both legs double confirmed)
  2. Bs/M, Mb/S (right leg and Mb double confirmed)

At the rate she was covering lakes, I gauged that Gabby would get to Upper Kaubashine on the 3rd, 4th, or 5th. I almost asked her to jump ahead to Upper Kaubashine, but I did not want to kill her momentum. But it was hard to wait and see whether the oldest known loon in Wisconsin, thirty-three-year-old “Red-Green”, had returned to her breeding territory.

When Gabby’s report came, it was not what I had expected:

Upper Kaubashine
Sooo the good news is I found the male (Cc&S, G/G – all confirmed) and that old female (S/Y, R/G – all confirmed). The bad news is the old female may have met the end of her tenure and potentially her demise at the hands (wings??) of an Unb, Unb (confirmed) intruder who was on the lake interacting with the pair when I arrived. I witnessed a VICIOUS 12 minute battle between the female and the UNB where they were latched onto each other’s throats and beating each other with their wings (both were covered in blood) for about 8 minutes, until the old female started fleeing underwater. But the UNB was relentless and pursued her, beating her the whole way. Then the old female finally made it to little islet and looked like she was trying to find a place to go on shore, but ended up being trapped against the islet while the UNB continued to stab her with her beak and beat her. The old female finally gave out a two note wail and then the UNB finally stopped and left to go preen elsewhere. I thought the old female could be dead already, but when I left her at the shoreline she was still turning her head. I hope she can hide long enough to recover to get off the lake, but the way she was being attacked, it did not look good.

Although we have studied them for decades and know their behavior well, we find it freshly shocking to watch loons battle. The brawl that Gabby describes was more violent than any of the few dozen or so that I have seen over the years. Despite the whipping of wings and jabbing of bills that these fights entail, one almost never sees blood. However, what began as a stereotypical head-grasping and wing-beating contest, she reports, quickly morphed into an all-out struggle for survival — once resident Red-Green recognized that she was overmatched and her goal changed to self-preservation.

Physical features of a lake can play a role in territorial battles. In fact, a lake’s shape, size, clarity, and peninsulas and islands often determine whether a fleeing bird eludes its victorious opponent and flies off to a nearby lake to lick its wounds or fails to do so, suffers repeated pummeling, and ultimately dies on the lake it used to own. After the Upper Kaubashine battle, the clarity of the lake water made it simpler for Red-Green’s pursuer to track her underwater, complicating her efforts to reach safety. Thoroughly defeated but unable to elude her opponent, Red-Green was ultimately pinned against the long peninsula near the southern end of the lake, as Gabby describes.

We have no idea how Red-Green managed to escape the unbanded female’s grasp. What we do know, thanks to Linda’s visit to Upper Kaubashine today, is that, despite her dire circumstances two days ago, Red-Green is still alive. Linda was relieved to find her hugging the shoreline — as her photo shows — and skulking about under piers at the north end, while the male and his new mate cavorted far to the southwest in the protected nesting bay. Though clearly beaten up, Red-Green seems safe for the time being. Indeed, maybe she will emulate thirty-one year-old White-Yellow, a long-time breeder on West Horsehead. Evicted in 2019 after breeding on one lake for a quarter century, White-Yellow resurfaced this spring as the new breeding female on productive Little Bearskin Lake. In their tireless efforts to cope with defeat, bounce back, and resume productive lives, Red-Green and White-Yellow exemplify the dogged tenacity of female loons.

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.

At first glance, Bearskin Lake does not strike one as unique. It is rather round in shape, and, at 163 hectares, is much larger than our average study lake. But we cover many lakes rounder than Bearskin and several — including Two Sisters, Clear, and Minocqua — that are much larger. Likewise, Bearskin falls into the middle of the pack in terms of average and maximum depth. True, the lake bottom fairly seethes with rusty crayfish, but that nasty invasive species is also abundant in Oneida, Crescent, and Lower Kaubashine. What sets Bearskin Lake apart is not its shape, size, or biology, but the sort of loons that visit and live on it. 

I was reminded of the unusual status of Bearskin among loon lakes two days ago when I made our first visit of the year there. I was not greeted by the adorable sight of a loon parent capturing tiny minnows and gently leaning downwards to present them gingerly to its 3-day-old chick, as one might see on Silver, Hodstradt, or Bear. Nor did I encounter a male and female that had tried and failed to hatch chicks and were looking forward to next year, when they could renew their breeding efforts. Instead, I observed a nervous loon that immediately raised its head high upon surfacing to scan for a territorial pair that might take exception to its visit. (Linda’s picture above shows the alert posture characteristic of anxious loons.) This bird, “green over silver, white-blue over orange”, was a former breeding female on Seventeen Lake in Hazelhurst that we had seen only once since 2012. We have no idea what this loon has been doing since we last saw it, but its presence on Bearskin and without a mate suggests that it has been marking time and has not reacquired a breeding position. 

Three hundred meters southwest of the displaced Seventeen female was another forager that was far more relaxed on the lake. Like the first loon, though, she was alone. To my surprise, this bird — “silver only, white over yellow” — was the former breeding female from West Horsehead Lake. One of the most prolific breeders ever in our study area, this female has reared 19 chicks since her initial capture in 1996 and, at 29+ years, is our second oldest bird. Her residence on Bearskin solved the puzzle of her disappearance from West Horsehead, which Al Schwoegler (a West Horsehead resident) and I had been mourning all spring long. “Silver only, white over yellow” had finally met a young opponent this spring willing to fight harder than her for the territory. She had thus accepted defeat, left West Horsehead, and taken refuge on the lake where evicted adults have always gone — Bearskin Lake. 

I continued my paddle south from the boat landing, feeling that my effort to visit Bearskin had already been repaid. A lone loon foraging just west off the huge island diverted me briefly; I was deflated to find this bird unbanded. As I veered southeast, following the arc of the island, I scanned eastwards and spotted an apparent pair synch diving (i.e. diving and surfacing together repeatedly). These two loons seemed to know me and were no trouble to identify. “Red-stripe over copper, silver over orange” was a vaguely familiar band combination, but I knew his mate, “red-stripe over silver, red over white”, very well indeed. Initially banded on 2001, this female has raised 10 young on Little Bearskin Lake and on Currie, where she had settled in 2015 after her eviction from Little Bearskin. The male with her, I now realized, was her new mate from Currie. 

As pleased as I was to encounter the tame pair from Currie, their presence on Bearskin was very bad news. They had hatched two chicks on about June 25th, and had lost one of those by the time Lyn observed them on July 2nd. Since parents attend and protect young chicks assiduously and since we have never observed both pair members to leave chicks unattended until they reach four weeks, the Currie pair’s presence on Bearskin signaled that they had lost the second chick not long after the first and were done breeding for the year. “What are you guys doing here?” I said with a mixture of sadness and disapproval. Bearskin is not a lake where loons go to celebrate their achievements. 

My visit to Bearskin ended with an oddity. As I was lamenting the Currie pair’s disappointment, they wheeled around and began tooting to signal the arrival of a flying intruder. The intruder obliged me by arcing towards the Currie pair and skittering to a landing only 50 meters west. The morning sunlight allowed me to read most of its “red-stripe over blue, white over silver” band combination before it hit the water. This male, I knew, was the current breeder from Little Bearskin. His arrival here was more bad news, because males rarely leave their territories during a breeding attempt. “Red-stripe over blue” circled tensely with the pair and then became aggressive, sending both Currie birds fleeing in different directions as he stalked them underwater. Maybe he was stung by his own breeding disappointment. A later check of the database showed that he and his mate had been sitting for at least 32 days on four eggs on Little Bearskin without a hatch. We can reasonably surmise that the pair abandoned a first clutch of two eggs in early or mid May, reused that nest by laying two more eggs with the abandoned ones still present, and now have failed in a second attempt — either because of black flies again or perhaps infertility of the eggs. So this has been a year of frustration on Little Bearskin, as well. 

I found two more unmarked loons along the west shore of Bearskin on my visit and no hint of a resident pair or breeding activity. In fact, most pairings on Bearskin are fleeting, and nests are scarce. The last successful breeding on Bearskin occurred in 1997, when a pair fledged two healthy, crayfish-loving chicks, repeating their feat from the year before. Since then there has been a smattering of breeding attempts, but none — to our knowledge — has produced a hatch. Moreover, no pair has ever formed a breeding partnership that lasted more than three years on Bearskin. Loons seem to sense something about the lake that humans do not. Bearskin is not a lake where you go to raise a family; it is a lake where you go when you have nowhere else to go. 

Although it sounds odd to say it, I often think that loons have considerably more patience and perspective than I do. Perhaps because I cover so many different territories, and because a year can go by between my visits to any one territory, my brain perceives that time is passing quickly there, and nothing is changing. This sometimes leads to frustration and overgeneralization. If I find a failed nest in June of one year and again during a May visit to the same territory the next year, I throw up my hands and conclude that the pair there is wasting their time. If on two separate visits fourteen months apart I find two intruders then three more intruders on a lake, I am apt to grumble (sotto voce): “This pair has intruder problems.” If two visits eleven months apart happen both to fall on weekends when many anglers are on the water, I become excessively concerned that the pair on the lake will soon fall prey to fishing entanglement. I suppose I am not the only person to rush to such conclusions based on fragmentary observations.

So it was almost a year ago, when I reflected upon the plight of an ABJ (adult banded as a juvenile) that had taken to stalking the Blue Lake-West territory. As you will see if you reread that post, I had grown pessimistic about the chances of that young female, “White-Green”, ever winning a breeding position on the Blue-West. White-Green, a ten year-old from Franklin Lake in Forest County, has lived for some years on Blue. She had challenged the Blue-West female for ownership at least twice that we witnessed — once in 2014, when she was only five, and once again just last year — and failed to evict the older bird on both occasions. It seemed to me that she had set her sights on gaining a breeding slot on one of the two territories on Blue and had perhaps forsaken all other possibilities. Having seen her fail twice to supplant the Blue-West female, I began to fret that White-Green would never settle.

White-Green, as it turned out, was playing the long game. She ignored the negative vibe from a grey-haired, middle-aged canoeist who visited her lake from time to time and waited. She watched for half a decade as the Blue-Southeast pair reared four chicks to fledging and the Blue-West pair raised three chicks….and waited. She witnessed the violent male battle and accompanying infanticide at Blue-Southeast in 2016, failed to take advantage of the ensuing chaos to land a breeding slot, yet waited still more. Six Mays came and went without any sign that White-Green might end her quest and finally breed. But two days ago, Elaina, Evelyn, and Tarryn found White-Green foraging near the nest platform with the Blue-West male as if doing so was the most normal thing in the world. The old Blue-West female, a 20-year-old hatched on Virgin Lake and White-Green’s former nemesis, was nowhere to be found. (We presume that, having been evicted from her position, she was cowering somewhere on this large lake, hoping to avoid White-Green.) So White-Green’s patience has finally been rewarded. Loons’ rigid, keratinized bills prevent them from ever smiling, but I have a sense that White-Green would have been doing so, if her anatomy had allowed it.

I have touched upon this theme before. A peril of longitudinal investigation is that one decides, after a period of time, that one understands the system. So it has been with the Loon Project.

For many years I have thought I had a good handle on territorial behavior. Indeed many aspects of the loon territorial system have become clear during the course of my work and are not in doubt. Both sexes usually fight to claim their territories and face the constant threat of eviction. Males, which establish strong ties to a territory through controlling nest placement and learning where the best nest sites are, fight harder than females, and sometimes die during territorial battles. Early senescence among males sets the stage for them to become very territorial and aggressive as they reach their declining years (their mid-teens in many cases), which seems a means to help them eke out another year or two on a familiar territory.

But I might have been off in my understanding of the role of lake size and body size in territorial behavior. I have always thought of breeding territories on large lakes as much sought-after, because large lakes have ample food for rearing chicks. (Small lakes, you might recall, run low on food for chicks, resulting in lower fledging success.) If large lakes produce more young, I reasoned, large-lake territories must be highly desirable. Competition must be fierce, then, for these territories. A recent analysis of territorial tenure — how long a male or female can hold onto their territory before getting evicted from it — has forced me to rethink the effect of lake size on territorial competition. The figure below is a plot of territorial tenure versus body mass for males on lakes smaller than 20 hectares (50 acres) in size (like Langley, whose current pair is pictured). As you can see, small males — especially those below 4600 grams — have very short stays on small lakes, in most cases, while large males — notably those heavier than 5000 grams — often enjoy very long territorial tenure. This pattern suggests that, contrary to my expectation, territorial competition is fiercer on small lakes than large.

impact of lk size, male body size, on terr tenure

Let’s look at the same pattern on medium-sized lakes (20 to 80 hectares; or 50 to about 200 acres). You can see that the overall pattern is still evident, although it is weaker here, because a number of very large males (5400 to 5800 grams) have anomalously short tenure.

i2 mpact of lk size, male body size, on terr tenure

Finally, let’s inspect the data only for males on lakes larger than 80 hectares (200 acres). In contrast to my earlier hypothesis, large males are not holding their territories any longer on large lakes than are small males, as you can see from the plot below. Males of all sizes may enjoy long tenure on large lakes.

3impact of lk size, male body size, on terr tenure

How on Earth do small males hold their territories much longer on large lakes — which  seem much in demand, get more intrusions, and appear difficult to defend — than on small lakes, which get fewer intrusions and should be more easily held? I don’t know exactly how males hide in plain sight on large lakes, but it might have to do with the difficulty that territorial intruders have in simply finding a nesting pair and identifying nesting habitat on large lakes. Consider the Lake Tomahawk-Little Carr pair. This pair nests in a marsh at a well-hidden location. When one bird is incubating, its mate is usually far off in the wide open portion of Lake Tomahawk, which is many kilometers long and has an area of 1400 hectares (about 3500 acres). A male intruder might well find and socialize with the off-nest pair member on on the big water, but it would have no way of knowing that the mate of this loner was on a nest hidden far away in a marsh. Similarly, when the eggs hatch, the pair quickly leads the chicks to the main bay of the lake, far from the critical nesting area. Pairs with chicks provide an enticing cue to young males seeking territories, because the presence of chicks tells of the availability of nesting habitat. But a male intruder that encounters the Tomahawk-Little Carr pair and their chicks on the main bay of the lake would face the needle in the haystack problem in locating the precious nesting area that yielded the chicks. A dangerous battle might win the territory, but the knowledge of how to use the territory (that is, where to place the nest) would vanish with the old male’s departure. Hence, large lakes appear to be less valuable to males.

A male intruder bent on taking a territory likely to yield chicks in the future would be better-served by evicting a chick-rearing male on a small lake. Such an intruder would have a much smaller set of nesting areas to inspect and would likely find and use the nesting area that produced the chicks. Thus, we might expect stronger competition among males for small, easy-to-learn territories — a pattern that dovetails with the longer tenure that large, competitive males enjoy on small lakes, compared with small, easily-evicted males.

What about females, you might ask? Do large females on small lakes, like large males, have an advantage in holding their territories when compared with large females on large lakes? If my hypothesis is correct, and the value of a territory depends upon knowledge of safe nesting areas, then large female size should not be especially beneficial on small lakes. Indeed, any impact of female body mass on territorial tenure should be equal across all lake sizes. Why? Because females do not control nest placement in this species. An intruding female that evicts a breeding female with chicks and pairs with the breeding male would have access to that male’s knowledge of nesting sites on a lake of any size. As predicted, large size is no more beneficial to small-lake females than large-lake females. (Indeed, size has an overall weaker effect on competitive ability in females.)

So my post hoc hypothesis for the fierce territorial competition on small lakes holds for the time being. The explanation I have given is not the only one consistent with these data, by the way. In fact, the entire complex pattern described above might be explained by a completely different scenario. Large males might hold small territories longer simply because they are in better body condition. This is highly plausible, because mass is a good predictor of health and condition. Thus, only large males might be able to hold onto small lakes for a long time, because they are in good enough condition to survive in a habitat with limited food. Small males, by this logic, are already in sub-prime condition, so they are destined to have short territorial stays on lakes with limited food. In contrast, medium-sized and large lakes do not show the pattern, because food is not limited on them.

As you see, we have a long way to go to figure out exactly what the above graphs are showing us. Distinguishing between the “small-lakes-are-highly-competitive” and the “holding-small-territories-requires-good-body-condition” hypotheses will take some years. The difficulty of using what seem like beautiful, clear data to reach a firm conclusion provides a nice window on what it is to be a scientist.

 

 

In my last post, I told only half of the story of the explosion of the Cunard family — the cheerful half. If you read that post, you know that, following the eviction of the Cunard male and abuse or neglect of the chicks by the evicter, one chick made a daring 1/4-mile trek across land to Hasbrook Lake and is now happily ensconced in that loon family.

The other Cunard chick was not so fortunate. In fact, following interviews of campers and the camp steward, we now know that a day or so before the eviction that led to the desperate dash of one chick to Hasbrook, its sibling had swallowed the live bait and hook used by a camper. As he described it to me, the fisherman panicked and did what most do when they have hooked a loon: he cut the line. I discovered the aftermath of this hooking. The thoroughly consumed remains pictured above suggest that the injured chick became weak, took refuge on shore (as seriously injured loons do), and was attacked and killed by an opportunistic mammal or scavenged after death. Its four leg bands confirmed its identity; the threaded line and fishing snap I found confirmed the cause of death. So the eviction that occurred on July 30th and 31st was actually the second unfortunate turn for the Cunard pair during the last three days of July.

We have discovered several such hookings during our study, despite the fact that anglers do not trumpet them. Perhaps we should take a moment to describe what to do when a loon takes your hook. The best outcome is removal of the hook by the fisherman. Removal of the hook gives the loon a good chance to survive the encounter. Cutting the line, on the other hand, frees the angler but leaves the hooked loon with a death sentence. A hooked loon (or other animal) on the end of a cut fishing line has to contend with a hook or lure that it probably cannot dislodge on its own. Its feeding impaired or prevented altogether, a hooked bird will probably succumb to starvation or predation resulting from its weakened condition. The second best outcome is to cut the line and immediately inform a local wildlife official of what has happened so that he or she can get help for the bird. In many cases, a hooked bird can be captured and de-hooked by me or someone else trained to do so. In other words, if you cut, don’t cut and run. Those of us who study and love loons will do our best to save one that is in trouble.

The Cunard chick’s death is a case in point. Had we known about the hooking, we would have had little difficulty re-capturing the chick and likely removing the hook as well. In that case, Hasbrook Lake might have ended up with four chicks rather than settling for three!

To those of us accustomed to looking at loons during the summer, the sight of an adult caring for three chicks — as in Laura Unfried’s photos from two days ago — is peculiar. Loons, of course, almost always lay only two eggs. If they are lucky, two chicks hatch. It is by no means certain that those two chicks will survive to fledging age. In fact, 47 of 61 breeding pairs we study have one chick, not two. So the spectacle of two adults caring assiduously for three young was startling.

Close inspection of Laura’s photo from Hasbrook Lake reveals another peculiarity: the central chick is much larger — perhaps 10 days older — than the other two chicks. (Note that the left-hand chick is entirely downy with a small bill, whereas the center one has the anterior part of its head coming into adult feather and has a bill nearly as thick as the parent’s.) The obvious size disparity told Eileen Lonsdorf, who reported the third chick three days ago, that her nicely balanced family of two parents and two chicks had been joined by an interloper.

How could a huge, healthy chick somehow get separated from its biological parents and join another family? Territorial behavior among loons guarantees that each breeding pair will nest and rear its young far from other pairs. The likelihood of a chick straying from its own family to join another — fortuitously or by design —

SONY DSC

seems remote.

One lesson that you learn if you do something for a long time is that rare events do occur. Chicks do very occasionally leave their parents and territory to join other families. We have noted two causes for such chick dispersal. First, starving chicks, especially beta chicks on small food-limited lakes that are being physically beaten by their alpha siblings, sometimes attempt to escape the abuse and find an alternate loon family nearby that will feed and protect them. Second, chicks that lose one or both parents to territorial eviction are forced to flee their natal territory and seek parental care elsewhere, if the adult that evicted a parent physically attacks them.

Solitary journeys by displaced chicks seeking new homes are desperate enterprises. One reason for this is that many lakes with loon chicks simply have no neighboring pairs with their own chicks that might be joined. Even if a displaced chick is fortunate enough to find a nearby pair with chicks, they are likely to be much older or younger than itself. If so, it is unlikely to be accepted by the new family. I vividly recall a case in 1999, when an abused beta chick undertook an astounding 1/2-mile trip across woods and roads from Benedict to Bug Lake in Vilas County, only to land with a foster sibling three times its size that beat it mercilessly until it perished.

Since the monster chick that joined the Hasbrook pair is a robust, well-fed individual, we could rule out that it fled to Hasbrook because of sibling abuse or lack of food. So we were left to conclude tentatively that a nearby territorial eviction forced this young loon to relocate. We pulled out a map to assess the possibilities.

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Immediately, we pinpointed Cunard Lake, which is separated from Hasbrook by a quarter mile of woods and bog, as the likely source of the wandering chick. Cunard, a regular study lake of ours, had two large, healthy, 5-week-old chicks at our last visit on July 25th. Yesterday, however, I found the lake empty of loons, except a single floater adult. The steward of the campground reported that loons had been chasing each other repeatedly across the water on July 30th and 31st, which indicated a protracted territorial battle. The absence of the territorial pair suggested strongly that the breeding male had lost the battle to a usurper and either died or been forced to abandon his territory and chicks. This tragic event, in turn, would have scattered the rest of the family and subjected the chicks to attacks by the new male owner.

Last night we captured the peculiar but close-knit family of two adults and three chicks on Hasbrook. It will require genetic analysis to be certain that the huge new chick on Hasbrook is a refugee from Cunard and the offspring of the displaced Cunard pair, as we surmise. But we have strong reason to believe that he is a most fortunate survivor of a desperate overland journey.

It is July and time to hide the chicks! That’s right; while human parents show off their progeny — perhaps partly to solicit help in caring for them — loons do the opposite. You see, intruders looking to evict territorial residents scour lakes for chicks, because the presence of chicks indicates that the lake contains good nesting habitat and abundant food. So by producing young, a breeding pair has put a giant target on their backs, providing an incentive for any intruder that discovers the chicks (like one of the six intruders shown in Linda’s photo) to return the following year and make an eviction attempt. We should expect, therefore, that parents would hide their chicks from intruders whenever possible.

Of course, breeding pairs are fighting a losing battle. On the one hand, they must feed and protect their chicks, which includes vocalizing often to warn their mate and chicks of passing eagles and other dangers. On the other hand, when intruders fly over or land, parents need to ignore the chicks altogether. Toggling between these two behavioral modes is no small task. Furthermore, while it is desirable to protect your long-term ownership of the territory by hiding your chicks from intruders, you do not want to lose them in the process!

Although chick-hiding is a tricky business, loon families do have a strategy for coping with the sudden appearance of intruders overhead, which fly over at a speed of about 70 miles per hour. We call it “dive and scatter”. At the appearance of a flying intruder in the distance, a loon pair and their chicks quickly slip under water. The chicks swim toward shore and, once there, are hidden by their brown plumage, which makes them resemble rocks or logs. Meanwhile parents swim under water to the middle of the lake, which draws the intruders to them and not the chicks. The aim of this coordinated behavior pattern by chicks and their parents seems clear: keep intruders from seeing the chicks. On its face, dive and scatter behavior clearly seems a means of helping parents’ maintain possession of their territory.

I need to pause here for a second to consider an alternative explanation for dive and scatter. In fact, the most obvious reason why a pair and chicks would dive and scatter is to protect the chicks themselves. Intruders do kill chicks commonly, so this is a viable hypothesis at first blush. But chicks are most vulnerable to being killed by intruders in their first two weeks, so dive and scatter as chick defense — if it is a viable explanation — should occur mainly among small chicks. Yet dive and scatter occurs rarely in small chicks and very commonly in those four weeks and older. So the hypothesis that dive and scatter is a behavior to protect small chicks from intruder attacks can be easily rejected by its timing.

We have known about dive and scatter behavior for some years, but yesterday on Woodcock Lake I learned that loon parents know when to call off the ruse. While feeding their single chick along the lake shore, the Woodcock pair spotted two intruders in flight. The family dove and scattered, the chick hiding near shore and parents making for the lake’s center, in stereotyped fashion. Following the script, the two intruders landed by the parents (and far from the chick), the four adults circling and diving together for several minutes. The charade abruptly fell apart when an eagle flew over the part of the lake where the chick was hiding. Both parents immediately ceased interacting with the intruders, wheeled towards the eagle, and wailed desperately for several minutes, while swimming in that direction. In a half-second, the breeding pair had morphed from cool, detached individuals with nothing to hide into into frantic worry-warts!

Some might view such a loss of composure by a breeding pair to be quite costly. If intruders are able to learn about the presence of chicks by detecting chick defense behavior such as that shown by the Woodcock pair, then the pair exposed themselves to the threat of future eviction by wailing to defend their chick in the presence of two intruders. A clear blunder….until you consider that the alternative was to lose the priceless product of their summer’s breeding efforts.