I think I have made it clear already that loons’ allegiance is to their territory, not their mate. That is, when offered a choice between abandoning a territory and following their mate after their mate has lost a territorial battle, loons always choose to remain on the territory and form a new pair bond with the winner of the battle. This behavior seems heartless, but it makes perfect sense, because loss of a breeding territory is a crushing blow that makes it impossible to breed. Mates, in contrast, are easy to find.

While loons routinely say farewell to breeding partners, 2020 has seen more of our breeding pair members change mates than ever before. The graph below shows the proportion of adult loons on a breeding territory in one year that were not on that territory a year later. As the graph indicates, some years have very stable pairs (like 2008 and 2019), while other years see lots of turnover among pair members. In 2020, one quarter of all breeding pairs experienced a loss of at least one pair member, and a sixth of these — 6 pairs of the 145 we follow — saw both members of the pair

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replaced by a new adult.

Of course, eviction is not the only factor that causes a loon that is on a territory in May of one year to be gone from that territory a year later. In fact, there are two main causes: 1) eviction and 2) death. Both of these biological processes contribute greatly — and about equally — to the failure of breeders to return.

Looking closely at the graph, you can see that annual return rate jumps around a good deal. Last year, for example, was a year when a very high proportion of all adult breeders came back to their territories of the previous year. (We can only speculate here, but these jumps are probably caused by occasional “die-offs” during migration or winter.) If you were looking at the return rate as a proxy for adult mortality, you might breathe a sigh of relief at this point; the graph does not seem to show an increasing trend in failure to return to territory that might mean increasing adult mortality over the years.

One final point. While it is true that failure to return to the territory does not obviously shift upwards or downwards over the past quarter century, careful readers of the blog might remember that the eviction rate has fallen dramatically in our population in the past two decades, because there are now far fewer nonbreeders seeking territories than there were 20 years ago. If evictions have declined over the years, then deaths must have begun to account for a growing proportion of all cases of non-return shown in the graph. Thus, it might actually be the case that adult breeders die at a higher rate now than they did a few decades ago, but that the graph does not show us the data cleanly enough to tell. In short, whether adult survival is trending downwards or not will not be clear until we do a more detailed quantitative analysis.

Oblivious to the territorial chaos swirling around them in 2020 — I mean loon-related, not human-related chaos — loons have been going about their business. Whether members of a growing or declining population, and whether their mate is new or old, most of our study animals have picked up the pieces after a devastating black fly season and renested. We still hope that these late nests will allow the population to generate enough chicks so that 2020 will not be our worst year ever for chick production. There is some comfort in the fact that chicks are produced one brood at a time. Perhaps the stalwart seven-year-old Pickerel-South male in the video below and his mate will contribute a chick or two to the total.




Most scientific research comprises snapshots of a biological system. That is, we usually study the behavior or ecology of an animal for a year or two in a forest, on a coral reef, or in a desert. On the basis of such a short term study, we pontificate about what constitutes a good territory and what constitutes a bad territory for the animal we are studying. Then, feeling that we have described the system accurately, we fold our tents and move on to the next study and habitat.

But time changes things. My team and I got a demonstration of the impact that time can have yesterday when we visited two lakes located towards the northern part of our study area. Life has always been hard for loons on Dorothy and Hodstradt lakes. They are both rather clear lakes and full of fish. But they have been disasters reproductively, because they lack the islands, marsh, and bog that loons seek out to keep their eggs safe from raccoons.

The gradual but now-dramatic rising of lake levels in the Northwoods has produced a spectacular reversal of fortune for loons on Dorothy and Hodstradt. What had been an unremarkable spit of land on Dorothy has become an island several meters offshore, reachable only by water (see photo below). What once was a long curving peninsula on Hodstradt has been transformed into an island, accessible only after a lengthy swim. In short, two lakes for which chick production was a freak occurrence have now become prime real estate, because they offer offshore nest sites inaccessible to all but the most ambitious raccoon.

Of course, the rising waters have not been kind to all lakes. Heiress Lake had a handy island that saw regular chick hatches in the late nineties and early 2000s. But no more. That raccoon-proof site is now four feet underwater, and Heiress no longer supports a breeding pair.

The take-home message is clear: territory quality is not fixed and unchanging. Instead, changing climatic patterns transform the landscape in surprising ways. A goldfinch’s lifespan is short enough that habitat transformations probably matter little. But loons live long enough to see poor nesting habitat become good nesting habitat and vice-versa; this species should be able to detect and respond adaptively to fluctuations in territory quality.

In fact, loons do exhibit some ability to respond to changing landscapes. We see this ability in the willingness of breeding pairs to explore vacant lakes near their original one and sometimes nest at sites different from those they have used to hatch chicks. And, of course, young nonbreeders use the presence of chicks on a territory as a measure of current reproductive quality so that they can target lakes for eviction attempts that will reward them with many offspring. On the other hand, many adults settle on a productive territory during the prime of their lives only to see its quality decline along with their own body condition. Lacking the fitness to defeat an opponent in a battle for a new territory, such birds are stuck breeding on a failing territory. These old codgers could tell ecologists a few things about territory quality and the passage of time. 

What has been most striking about the dozens of loon territories we have visited in the past week has been how similar they seem to be to loon territories in early May. At that time of year, pairs have mostly recovered from the energetic stress of migration and have shifted their focus to breeding. With ice gone from the lake surface and perhaps a territorial challenger or two repelled, breeding pairs can search for a nest site, build a nest, lay eggs, and — if lucky enough to have a safe nest site or to avoid attracting egg predators to a risky one — jointly incubate them for four weeks until hatching.

Though the ice is long gone and challengers long since defeated, most loon pairs (over 90%, by our preliminary estimate) now face the same long slog of incubation they encountered a month ago. Having had their first nesting effort obliterated by black flies, these pairs now must start over from scratch. Thus, the video below depicts a common sight: a pair that has chosen a new nest site, started to lay eggs, and must work together to hatch chicks. These two birds, a 7 year-old male from Hasbrook Lake (background) and a 10 year-old female from Day Lake in Vilas County, seemed to contemplate this task with a degree of circumspection.

As nasty and harmful as black flies are, they are not as bad as egg predators. Flies are only really abundant for three weeks or so, whereas egg predators are always present. Loons behave as if they understand the time-limited threat that black flies pose. How? They commonly reuse nest sites that contain eggs from an attempt ruined by black flies, whereas they almost never reuse nest sites in the wake of egg predation by a raccoon or another predator. (Our recent paper describes this logical response to black fly abandonments.) Sometimes a males’ love of a nest site is so strong that he chooses it even though it still contains two eggs from the previous nesting attempt. In such cases, a loon nest contains two viable eggs from the renesting attempt and two duds from the abandoned effort weeks earlier (see the photo at the top, from Little Bearskin Lake this year). We often wonder how the sitting birds manage to cover and warm the eggs such that the good ones hatch.

In short, there is a new round of nests in the Northwoods of Wisconsin. During the past several days, as we have found pair after pair laying a second round of eggs and forging ahead in the hopes of raising chicks, it has raised my spirits. We will never look back at 2020 as a banner year for chick production, but the loons are not giving up.








My new team and I are racing around the study area, still catching up to our banded breeding population. At each lake, we record the bands of the female and male, look quickly for any active or failed nests — only in obvious places — and race to the next lake to repeat the process: (“Ok…the female has a yellow band on right and is red over green on left? Good enough….let’s go!”.) The work is frantic and exhausting, and we are only halfway through. We are all so busy covering lakes that there is little time to reflect on what we have seen. I have trouble remembering what lakes we have even visited at the end of each day, so anxious am I to eat a meal and hit the hay for the next 5am wakeup.

Yet some patterns have emerged from our lake visits that remain lodged in my brain. It has been a dreadful first round of nests for most breeding pairs. Typical pairs in the study area abandoned their first nesting attempt three to four weeks ago because of the clouds of flies that descended upon them and have only just begun to renest or think about doing so. Based on what we have seen, it appears that 70 to 80% of all pairs could not stand to incubate the first clutch of eggs they laid in early to mid-May, making 2020 even slightly more devastating a black fly year than 2014, the previous worst year on record. Our study population has seen a steady slide in chick production over the past quarter century; 2020 will only strengthen that demoralizing pattern.

So you can imagine how it warmed my heart to hear about Linda’s loon pair (“Clune” and “Honey”), who managed to buck the trend and stick it out through all four weeks of incubation. At a time when the population as a whole is reeling, the assiduous parenting on display in Linda’s video below took my mind off of the population’s struggles for a moment and reminded me that good things can still happen.

There was something distinctly wrong with the Buck male. He had never been tame. Indeed, he was one of those loons that made you work to see his leg bands on each hourlong visit. So, a few days ago, as I hefted my canoe down the steep paved road to the public beach that we use as our access to the lake, I knew I would face a challenge to get enough good looks at his legs to produce a convincing ID. But the male that foraged all around the lake with the usual female was well beyond a challenging ID. He was somewhere between highly vexing and impossible to identify. While the female gave me occasional good looks at her leg bands as I tracked her loosely during her foraging routine and seemed indifferent to my presence, her mate clearly avoided me and gave me no close looks at all. This was a reversal from two decades of past observations on the lake during which the female, not the male, had always been the tougher ID on Buck.

I paused at intervals to consider a change in tactics. But there is not much flexibility and creativity involved in IDing loons from colored leg bands. One simply approaches a breeding pair closely enough to see any bands on the loons’ legs but not so close as to upset the birds — and hopes for the best. This undertaking takes great patience and some luck, especially at times when black flies are out in numbers, as they are now, because loons shorten their above-surface time and seldom preen when hounded by flies. In an attempt to rally my spirits through distraction, I stopped tracking the pair after about an hour and circled the small island in the southeastern corner of the lake. Denying what was clearly a move borne of frustration, I told myself that taking my eye off of the foraging pair for a moment would allow me to search for a possible abandoned nest on the island. After all, I was weeks behind schedule in this first visit to Buck, and an experienced pair like the Buck pair should have long since started incubation.

No nest was evident on the island, but my effort to avoid for a moment the exasperating task of IDing the male ended up solving the puzzle of the male’s identity entirely. Draped over a fallen red pine on the south side of the island, I found the carcass of the Buck male that we had banded way back in 1999.


It was sad to see silver over blue, red-stripe over red gone forever after watching him vigorously defend his territory for 21 consecutive years and never lose it — even for a day — in all that time. But it is the ultimate fate of every territory holder to meet a fitter, stronger, younger territorial opponent and bow to them. That is the essence of terminal investment in old male loons. The death of this oldest male in our study area (26+ years) now leaves the placid 24+ year-old Bear Lake male as the most senior representative of his sex. I am hoping the day on which the Bear male meets a determined, superior opponent in a territorial battle is still several years away.

I have had a whirlwind last 24 hours. It began last night just after 10pm (Pacific), when I realized that I did not have the key to the storage unit in Rhinelander where we leave our car over the winter. No, I thought, that key is in lockdown in my office at Chapman. An hour and a half later, I had convinced campus security to let me into the science building, retrieved the key, and returned home to Irvine. At that point, I had about 4 hours of sleep to look forward to before heading to LAX and thence to Rhinelander. As I tossed and turned, trying to empty my mind for sleep, I burned more potential hours of rest. In the end, I got about two and a half hours.

But the worm turned during my trip. I polished off a troublesome article review assignment on the plane, dozed a bit afterwards, and arrived in Rhinelander before 2pm. Following an awkward and damp 2-and-a-half mile trek along Highway 8 to the storage box, I tasted sweet victory as the Toyota Corolla I had moth-balled in August instantly purred to life. The disaster of a dead car battery averted, I was suddenly ahead of schedule, so I stopped off at my first lake of the year — Townline, just west of Rhinelander.

Though observing loons on Townline Lake means putting up with the constant whizzing by of cars on County K, Townline has always been one of my favorite lakes. Most of my affection for the lake took root during the residency of a long-term breeder —a very approachable male who defended the territory for at least 24 years, 1994 to 2017. But somehow my warm feelings for S/R,O/G turned into love for the lake, and now I look forward to every visit there.

I was instantly rewarded for my short walk down to the lake’s edge today, when a foraging loon surfaced less than 10 meters from me. The bird made a series of short dives, spending — it seemed — as little time as possible on the lake’s surface. Even so, at that range I had no problem determining that it was unbanded. This surprised me, because the Townline pair, as of August 2019, consisted of a twenty-something female (banded on the lake in 2002, as an adult) and her young mate — the 7-year-old male from Anvil Lake in Vilas County that had replaced my favorite male loon when he failed to return from the winter in 2018. The presence of an unbanded loon that acted very much at home on Townline showed that at least one of these two pair members had not returned from winter or had been evicted from the territory.

I should point out that quick dives and endless foraging bouts, such as I saw today, are the rule during 2- to 3-week-long black fly outbreaks. That is, loons dispense with resting and preening during peak fly season; instead, they spend as much time as possible under the water to avoid the flies. I often wonder what they are doing during these bouts. Since the bouts consume far more hours than loons need to satisfy their energetic needs, they must spend some of this dive time simply swimming underwater, while ignoring any and all terrified fish they pass. So I guess it is not relaxing to be a bluegill during black fly season either!

The black flies that so pester loons have no taste for human blood, but even we human observers dislike them. Abundant flies complicate our efforts to ID loons from leg bands, which is easiest during preening and resting. Indeed, it took me almost 40 minutes to even locate the mate of the unbanded loon I first saw foraging near the shore this afternoon. This second bird too was dodging the relentless dipterans, diving constantly and spending only a few seconds on the surface between bouts. Luckily, this individual was tame and turned out to be the now-8-year-old male hatched on Anvil. When he began cozying up to the unbanded bird I had seen earlier, it became clear that the old female is gone from Townline.

I looked quickly for a nest, circling the little island that the Townline pair almost always uses. I found nothing and suspect that to the female turnover and the black fly abundance together have pushed back nesting at least four weeks on Townline this year. Judging from the cloud of hundreds of flies that hounded (but did not bite) me as I searched the island, several more days or a week will pass before this new couple can consider laying eggs. As thick as the flies were today, they were worse ten days ago, as this video shared by Linda shows.

So I guess we can take heart that we are moving in the right direction!

Caught up as I am in the mad scramble that teachers and students face at the end of the school year, I have been unable to keep up with events unfolding in the study area. I am sorry about that. Of course……I am also not in the study area, so I have to rely upon accounts of loon activity from Linda and others who are able to see the birds!

The loons in northern Wisconsin seem oblivious to the pandemic that is plaguing humans at the moment. They have their own problems to worry about: other loons, eagles, and their early-season nemesis, Simulium annulus. During the past week or so, populations of this black fly have exploded, causing headaches for loons across the study area. (Thanks to Greg and Al for their reports of fly activity on their lakes.)

You might wonder why I use the scientific name of the species of fly that harasses loons. When humans are pestered by insects, we often think of the little varmints generically. That is, we place biting insects into classes that represent several or dozens of species — mosquitoes, black flies, horseflies, no-see-ums. Our crude classification scheme makes sense, because the behaviors of different species, the habitats where we find them, the timing of their attacks, and our strategies for eluding them are often similar across species. But loons face a laser-focused attack by females of one species of black fly whose sole purpose in life is to find a loon, extract a blood meal, and nourish their eggs with it. I loved this photo that Linda sent me

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several days ago, because it illustrates two intriguing biological patterns. On the one hand, Simulium annulus makes life a living hell for loons for a few weeks every spring, as one can see from the cloud of flies on and around the head of the male loon in the water. (This bird is trying to work up the gumption to get back on the eggs.) On the other hand, S. annulus leaves all other birds alone, even those in plain view a few meters away (note the carefree Canada Goose standing on the island in the upper left corner).

It has been a rather cool spring in northern Wisconsin, and that is bad news for loons, as cool weather keeps female S. annulus alive longer than usual and prolongs the window during which they harass incubating loons. Reports so far suggest that there will be widespread abandonments of first nesting attempts, although some breeding pairs — like Linda’s intrepid duo, Clune and Honey —  are so far enduring the welts and refusing to give up on their eggs. The coming weeks will tell us whether 2020 is a horrendous year for black flies, like 2014; a bad one, like last year; or an average one, like 2018. It pains me to say it, folks, but we are hoping to be average!

Let me end on an up note — well….kind of an up note. Our paper that reports reduced chick production, lower survival of young adult loons, and a decline in our study population has been well-received by a scientific journal. Thanks to everyone who helped with the decades of data collection that culminated in these findings and to our many supporters (including many who follow this blog) who made our work possible. During this year and the next few, we hope to learn what is causing these declines and to see if we can do something about them.

I just read a story about an Arctic research team that has been hamstrung by the pandemic. They are trapped in quarantine in northern Germany, awaiting the all-clear before they can conduct their crucial research on the melting patterns in polar ice. Their vigil is especially tense, because rising spring temperatures are likely to set in motion the very melting patterns they spend all year planning and waiting for before they can reach the Arctic to document them.

Although their situation is more dire and their mission more vital than my own, I know how these scientists feel. Recently, we too had to scale back our research efforts owing to the pandemic by abandoning plans for a thorough early-season census. Meanwhile, the virus-free loons have returned to their territories and are going about their nesting preparation, as they always do. They must be wondering where the inquisitive humans in their red canoes have gone.

Our field effort is not at a complete standstill. In fact, Linda has heroically visited dozens of lakes in the southern portion of our study area to ID returning pair members. She is perfecting the art of recording loon bands while keeping one eye on her grandkids! And Al and Nigel have patiently documented the male and female returnees on West Horsehead and Sherry, respectively.

Reports of loon activity of any kind are invaluable to us. Please send notes, photos, and any other records you might have of loons on our study lakes. These reports might be very basic, like: “I saw no loons on my lake until May 6th, and now there is only a loner.” or “There is a breeding pair on my lake, and I have seen them multiple times since ice-out”. A report might include a smidge of info on identity like “There is a regular pair on my lake; our neighbor spotted a red band on the left leg of one of them, when it preened”. And a few over-achievers might get very detailed information, like: “A loon pair was first spotted on April 26th. The male’s bands are copper over green on right and red over silver on left; the female is silver over blue on right, green over mint burgundy on left. They have a nest that we first noticed on May 8th on the south side of the island off the boat landing; GPS coordinates are N45.70063, W089.62474. The male engaged in a lengthy battle with an unbanded intruder on April 26th, during which he lost some feathers just behind his right eye.” Anyway….any loon-related info that you send us from our study lakes is greatly appreciated, because we have no data at all from 80% of them. Photos are tremendously valuable too, especially if they show a colored leg band or two that we can use to ID an individual. The earliest most of the team can possibly arrive in Wisconsin is May 27th. Thanks for any info and photos you can send to me at wpiper@chapman.edu to help us fill in the gap in our records. 

Stuck in southern California as I am, I have become fixated on the changing seasons in Wisconsin. Although recent days have been wintry in Oneida County, typical May conditions are a few scant days away. Nesting has already begun; Linda’s breeding pair shrugged off some early territorial excitement and are now sitting on eggs — while all of our team members except Linda are sitting in lockdown.

Yet there is great hope for the research team this year, once the virus releases us from its clutches. Following decisions yesterday by my daughter and a friend of hers from college to devote their summers to helping with our research, we now have four new recruits to the project, two postdoctoral fellows from Chapman, and yours truly — seven researchers in all. This is an embarrassment of riches, because we now face the dilemma of how to equip and house all of these folks.

This brings me to the burning reason for my post. Please let me know if you might have space where some of the team can stay. While we have comfortable housing for a team of 3 or 4, thanks to the continuing generosity of friends of the Project, we have now outgrown it, and need to add additional housing (near Rhinelander, if possible). Secondly — in keeping with our lean research model, which maximizes lake coverage — we need 2 to 3 more vehicles so that each team member can visit lakes on their own. (I have recently learned the good news and bad news about renting cars for 21 to 24 year-olds: the good news is that it can be done; the bad is that it costs twice the normal rate, so that no one in their right mind would do it!) I would happily commit to: 1) paying a fee for the use of a vehicle from about 7 June to 31 July, 2) maintaining any loaner that folks might provide in good condition throughout the summer, and 3) repairing any damage to such a vehicle that might occur during our research effort. Please contact me at wpiper@chapman.edu, if you can help with housing, vehicles, or both. 

Meanwhile, we continue our social distancing. Each passing sunset reminds me that time is marching on and that the loons are going on with their lives, despite our absence. Like the international crew in Germany, I wonder when on Earth I will be able to get back to my life’s work.

Identifying a loon from its colored leg bands is an incremental process. Once you spot a loon on a lake and approach the bird, you must develop a seat-of-the-pants strategy for recording its bands. The ideal situation is when you observe a preening loon, paddle slowly over to it, and simply wait for the bird to swing its legs up out of the water while distributing preen oil all over its feathers. One generally has at least five minutes to piece together the complete combination of four leg bands of preening birds from a quick view here or there. I talk to myself while getting bands, in hopes that I will remember what I have seen. “Yellow on top, right leg…wait….yellow over mint on right!” If the loon is not preening but foraging, identifications can take hours, and you must hope that, as you remain as close to the forager as possible, it happens to surface right next to your canoe and in good light when you happen to be looking its direction. In such cases, piecing together the bird’s band combination can be an arduous process, because one gets very quick views of bands underwater or for an instant just as the bird plunges beneath the water.

Despite diligent efforts, we often end up with only “partials” on loons’ bands during our hourlong visits to study lakes. However, since most of the loons we see are territorial birds on the lakes where we color-banded them, partials are often good enough to tell us the identity of the bird. Then again, sometimes — especially early in the year — we get surprised by a loon that was not banded on the lake where it is spotted.

Imagine what Linda must have experienced on Halfmoon Lake yesterday. After spotting a lone bird, Linda was expecting that it would be one of the two banded pair members from Halfmoon. She was no doubt pleased to see that the loner was preening, which gave her hope that she could nail its bands before it resumed foraging. Was this bird going to turn out to be “Grandma”, the female originally banded fourteen years ago on Muskellunge Lake, who had earned her name when she intruded onto Crystal Lake in 2015 at the time her son was rearing her grandchild? Or would the preener prove to be the rather skittish male from Halfmoon, which we had finally caught and placed bands on last July? As Linda’s crisp photo shows, the preener was “Yellow over Mint, Silver over Red-stripe” — neither Grandma nor her evasive mate. 

Linda knows this surprise visitor to Halfmoon better than anyone. You see, Yellow over Mint is “Mabel”, the female that has been a regular intruder into Linda’s lake since 2011. Years after Linda and our team had begun reporting Mabel as an intruder on our lakes, we expanded the study area to include Mable Lake and learned that Mabel was not a roving nonbreeder but the breeding female there. Mable is a tiny 25 acre lake near Tomahawk. With food so limited by the size of the lake, Mabel and her unbanded mate have struggled reproductively. Twice in the past three years the pair has hatched a chick but lost it at six to seven weeks of age — just on the brink of fledging.

Mabel’s breeding woes pale in comparison to the nightmare that befell her in 2019. As I described in a post last summer, Mabel swallowed someone’s fishing line on about June 20th of last year, was incapacitated by lead toxicosis, and only survived owing to Raptor Education Group’s heroic emergency surgery and extensive efforts at treatment and rehabilitation. Rescuing Mabel from lead sinkers was only half the battle. Although the REGI team had done what they could to feed her and get her fit for release, it was far from certain that she would be able to recover sufficiently to survive in the wild. In fact, we lost track of her after she was let go last July on Lake Alice. We simply hoped for the best, knowing full well that few loons survive a severe bout of lead poisoning.

Yet there Mabel was yesterday, looking (according to Linda) none the worse for wear. Indeed, having survived two migrations since her debacle, she has clearly returned to form. Mabel is still not back to her former status; she has lost her territory and joined the ranks of the many displaced female breeders who wait — often for years — for breeding vacancies to occur. But just surviving long enough to join that queue is a huge victory for Mabel — and for those of us who dared to hope that she could come back.