There was no good reason for the Crystal female to defend her nest. I had confirmed the colored leg bands on her mate, and he was no longer the male with whom she had mated and laid eggs on the platform. Instead, he was the neighboring male from Halfmoon, who had left there under mysterious circumstances. Lake residents had reported a “ruckus” early this morning, and that ruckus had turned the 14-year-old male who had been her steady partner for 5+ years (lake residents had nicknamed him “Walter” — not after me but after the largemouth bass in “On Golden Pond”, which features loons) from an expectant father into a displaced, childless nonbreeder. Walter’s eviction meant that any ongoing reproductive attempt was over, as evicting males and females have no interest in incubating eggs or feeding young that are not their own. Yet the Crystal female — lake residents named her “Katherine” because of Katherine Hepburn in “On Golden Pond” — felt an inescapable attraction to the nest. As I approached to inspect the four defunct eggs on the platform, Katherine showed classic nest defense, swimming twice under my canoe. The evicting male from Halfmoon preened indifferently 100 meters away, as if willing to indulge his new mate’s obsession with her past nest but hoping she would get over it soon.

I witnessed a related behavior pattern on Swanson Lake just yesterday. There a mammalian predator (probably a raccoon, according to a camera study conducted some years ago by the Wisconsin DNR) had taken the two eggs that the Swanson lake female had laid in a second nest on the west end of the lake to replace those abandoned during the black fly period (see photo). When I arrived at first light, the female was alone, wailing intermittently, as loons do when their partner is not present. Forty minutes after I arrived, the male flew in, and he swam purposefully over to the newly-failed nest and climbed onto it. For three minutes he sat contentedly on the nest, as if all was good in the world. Then, he stood up on his legs and reached his bill downwards to turn the eggs, as loons habitually do. He seemed to put two and two together when he found no eggs to turn; afterwards, he sat only a few moments more before climbing down off of the empty nest and joining his mate in the water.

Despite 28 years of observation, I had never witnessed loon behavior that reflected slowness or inability to adjust to a new, stark reality — or perhaps I had simply not seen such behavior twice in so short a time, which made it impossible to ignore. As humans, of course, we have all behaved in such a way. That is, we have forgotten for a moment that some abrupt, fundamental change has occurred in our lives and mistakenly acted as we had before the change. Over a longer timescale, I find myself behaving so now. On each visit I make to a study lake in mid-June I expect to see young loon chicks or a pair late in the four-week incubation stage and on the brink of a hatch. But like the Crystal female and Swanson male, I find myself slow to adapt to a new reality — almost universal abandonment of first nests, many pairs without chicks or nests, and a great big dent in the breeding success of the population.

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

Screen Shot 2020-05-19 at 8.44.40 AM

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.

It was jarring two days ago to look at the database we use to track our breeding loons. During most years, the first week in June is the peak of incubation. At this time, breeding pairs that laid eggs early are well into the 28-day period that will carry them to hatching; others have lost an early clutch and replaced it. But steady, determined incubation is the rule at this time of year.

Not so this year. As the screen grab from Evelyn and Tarryn’s data entry shows, 2019 is yet another year of severe black flies. I had a sinking feeling that black flies would be a plague when I was in the study area in May.

As our recent paper shows, cool springs are killers. In years when April and May are cooler than average, black flies live longer than average. From the standpoint of a female fly, cold weather makes flight and dispersal more difficult, so a female in a cold spring is likely to delay her quest for the blood meal she needs to nourish her eggs. Not all females postpone reproductive activity, however, so cold springs reduce synchrony between female flies. The result, from a loon’s perspective, is a longer period when flies are around to harass them on nests. In contrast, warm springs cause a well-synchronized explosion of fly biting activity. During warm years, Simulium annulus blackens the skies for a few days and exacts an awful toll on incubating pairs during that brief period. Many pairs, though, are able to weather the onslaught, maintain viable eggs (no doubt aided by warm temperatures), and incubate the eggs to hatching despite the interruption.

Screen Shot 2019-06-10 at 9.31.33 AM

Elaina’s photo of the nest on Hilts Lake is typical of what we see in a cool spring. Flies are abundant, to be sure. In the photo, you can see many in the air above the nest but also scores hanging onto the arched roof on this platform. There are enough flies around the nest to keep the pair from incubating the eggs, but few enough so that this infestation does not reflect an explosion, such as would occur in a warm year.

Screen Shot 2019-06-10 at 11.07.16 AMNow that I have got you worried — sorry — you must be wondering where 2019 ranks relative to other years. What kind of productivity can we expect? I ran a quick back-of-the-envelope analysis by comparing rate of chick production in each year with the proportion of pairs sitting on nests during the first week of June. Even with the one “outlier” (2013), there is a tight correlation. That is, we can usually tell pretty well how productive a year our loons are going to have by looking at the proportion of all pairs on eggs in early June. If 2019 falls near the line, then the 0.45 proportion of sitting pairs in early June of this year predicts 0.42 chicks per territorial pair. This is not terrible — look at 2011, for some perspective — but not what we had hoped.





It is my 60th birthday today. I ran 5.3 miles just to show that I still had it. Since I find running unpleasant, I listen to music in an effort to distract myself as I run. (This works poorly.) Amidst the classic hits on my playlist today (by Jim Croce, Don Henley, Talking Heads, David Bowie) was an outlier: “New Rules“, a 2017 hit by Dua Lipa. Wikipedia describes New Rules as a “tropical house, electronic dance music and electropop song with a drum and horn instrumentation”. While I do not understand most of that description, I understand enough to know that few men my age would find the song meaningful. When you consider that the song concerns a young woman’s efforts to break up with an unfortunate boyfriend, its profound significance to me becomes even more alarming.

I can explain. New Rules describes a very logical practice common to many of us: trying to interpret a vexing phenomenon and chart a course forward by looking, not at a single event, but a series of related events. The idea, of course, is that an isolated event might be misleading, whereas many events, studied together, offer a better picture of the world. And this is what scientists like me do. We resist the temptation to generalize to the world from a single event and instead study sets of related events and use statistical tests to discern patterns that may or may not align with our hypotheses. When I heard New Rules for the first time, I laughed out loud, because Dua Lipa sings “Now I’m standin’ back from it, I finally see the pattern” — referring to her boyfriend’s persistent misbehavior. This is just exactly what I have devoted my life to doing… a very different context.

Here is the latest puzzle in which I am trying to see the pattern: old female loons are reluctant incubators. That is, when sitting out in the open on a nest becomes unpleasant, old females are less likely to put up with the unpleasantness and continue sitting on the eggs. Instead, they tend to bail on the breeding attempt, to their great cost and that of their mate. In loons, of course, the unpleasantness derives from black flies that specialize on sucking loon blood, Simulium annulus, which are in profusion at the moment in the study area. (The photo below is from Clara Lake, where the pair is beseiged.)

2019-05-17 09.45.12

I observed the reluctance of an old female to sit on eggs on Oneida-West four days ago. The very tame male that just took over the territory this year  — a 9 year-old hatched on McCormick who settled first on Oneida-East, and then shifted to the territory on the opposite end of the lake — had a nape that was seriously chewed up. The feathers on his nape were misaligned, showing that the skin beneath them was swollen from countless bites of black flies. Disrupted nape feathers are a telltale sign that the loon has been incubating for a long period in the presence of many black flies. But the female of the pair, a veteran of 23 years breeding on Oneida Lake and mother of at least 18 fledged chicks, had a pristine nape. While her appearance was more pleasing to the eye than the male’s, it revealed her dark secret: she had been neglecting her incubation duties after laying an egg in the nest a few days before.

One pattern is clear here. Statistical analysis of known-age breeding pairs has shown a very strong tendency for pairs containing old females to abandon their eggs when black flies are severe. In contrast, old males, young males, and young females incubate clutches enthusiastically when black flies abound. Why on earth would old females have evolved to drop the ball on incubation as they do?

As a biologist, I have learned that most behavior is adaptive — it tends to increase the breeding output of the individual displaying the behavior — so I am inclined to interpret what might be called irresponsibility on the part of old females as calculated to help them in the long run. Perhaps old females have somewhat weaker immune systems than young females, so that exposing themselves to countless bites and the harmful protozoans that flies transmit might weaken them, making them vulnerable to territory eviction by a healthier female competitor. By refusing to incubate and weaken themselves, old females are costing themselves a single chance to rear young but might be protecting their ownership of the territory, which increases the young they raise down the road.

My explanation for old females’ behavior is just one possibility. It is quite likely to be incorrect. Like Dua Lipa, I will have to stand back a bit more — and collect more data on old females — to see the true pattern.

What is better than finding out that your just-published article has been featured by an online science media outlet? Finding out from your dean! An hour ago this happened to me as I strolled out of our new science building.

We were excited to learn this article has excited some attention. It was a bit of a sleeper. Published in a good — but not spectacular — journal, our investigation of the flies’ impacts and loons’ logical responses to them caught the eye of the journal’s media department. I will not bore you by rehashing our findings, which I have discussed before. By the way, a related media blurb included Linda Grenzer’s cool photo of the male on her lake sticking on the nest in 2017 despite flies biting him mercilessly. (Another of Linda’s related photos appears above.)

Fortunately, this year has been a mild one for black flies. So while pondering the harsh negative impacts that black flies often have on loon nesting behavior and breeding success, we can all relish their absence.