Few loons have endured the frustrations that the current Mildred female (“Taupe Stripe”) has. Initially captured and banded on Soo Lake in 2004, she reared two healthy chicks with her mate in that year. But each year since has yielded no offspring for this bird, despite consistent effort.

Taupe Stripe’s struggles started when she was evicted from Soo by a stronger female in 2006. Thus began an itinerant lifestyle: temporary settlement as a loner on Goodyear Lake and frequent intrusion into other lakes in the area, probing for an opening. In 2010, she finally secured and defended a breeding position on Maud Lake. Like other small, shallow lakes, though, Maud suffers from a limited prey base. Efforts by the loon pair there in the three years before her arrival were excruciating — hatched eggs followed by starvation of chicks in the 2nd week of life, the first week, and then the fourth week. Taupe Stripe and her two mates fared no better, failing to produce young in 2010, 2011, 2012, and 2013. She fell off our radar in late 2013 and 2014, but resurfaced in 2015 and 2016 — again, as a floater.

When day to day survival is a challenge, as it is for loons, you focus on the present. Taupe Stripe ultimately settled on Mildred Lake in early 2017. Unlike Maud, Mildred is a large, clear lake with a strong record of fledging chicks that hatch. Although she and her unbanded mate lost a small chick on Mildred last year, they have turned things around. Last week we caught Taupe Stripe, her mate (now banded), and their strapping six-week-old chick. Things were still looking good for the family upon my visit there today. And thirteen years of pointless wandering, frustration, and disappointment are forgotten.

For the past several years, I have begun to turn my attention to the effect of lake size on breeding success of common loons. Clearly loons on large lakes produce more and healthier chicks than those on small lakes. We showed that on our paper from six years ago. This raises the question of why loons ever attempt to breed on small lakes. They are doomed to failure — or at least to greatly reduced likelihood of success. The water is muddied further by the fact that loons reared on small lakes prefer to breed on small lakes themselves. That’s right: chicks fortunate enough to avoid starvation on small, food-limited lakes replay the whole scenario as adults, subjecting their young to the same travail they themselves faced.

The puzzle of loons breeding on small lakes was thrown into start relief again yesterday, when I visited the Wind Pudding-West territory on a scouting trip for nocturnal capture. After not finding the chick and parents in the shallow bay on the lake’s western side, where we had seen them on previous visits, I headed towards the channel that connects that bay with the main lake. I was crestfallen when I reached the channel, as it was choked with lily pads and grasses to the point where it was difficult for me to find a passage through — even in a canoe. This discovery led me to doubt whether the pair might lead their chick through the channel and into the main lake as a means of finding more food for it. I began to fear that — walled off from an abundant source of food — the chick had probably starved to death on the shallow western bay since our last visit.

I had underestimated the determination of the pair to provide for their chick. As I paddled to the end of the navigable portion of the channel, I heard a chick’s desperate cries to its parents. I spotted the chick about half way across the marshy isthmus that now separates the shallow western bay from the main lake. The isthmus is no more than 20 meters wide perhaps, but it is densely overgrown with marsh grass to the point where the chick — equipped only with legs at the very posterior of its body — was forced to lunge awkwardly forward in order to make headway towards the main lake. To make matters worse, the chick had no clear idea of where it was going. I caught the chick’s initial confusion on video, as it sits within the marsh grass, uncertain how to extricate itself.

The second installment shows the chick after it has blundered around in the grass for a time but finally gotten a sense of where its parent wants it to go. The chick stops to give a distress call, then hears its parent call to it, which seems to give the chick the strength to complete its journey. (Apologies for the nervous narration and grainy video!)

The fact that the parents can entice this year’s chick to cross the isthmus and take advantage of food in both the western bay and main lake means that they are better off than they were here in 2016, when a chick wasted away and finally died of starvation. However, we caught the chick and female in the video last night. They are both severely underweight. The female, in fact, has the lowest mass we have ever measured for an adult loon. So even if the pair can find enough food to fledge the chick, chick-rearing seems to have taken a toll on the parents. Add yet one more item to the growing list of reasons to avoid breeding on small lakes with limited food.

The deformity was obvious back on May 17th, when we first saw her. The breeding female on Johnson Lake had part of her bill jutting upwards at a crazy angle. At first, viewing her at a distance, we thought that the dark spike that appeared to emerge from her bill might be a lure of some kind that she had latched onto mistakenly and been unable to dislodge. But, as Elaina’s photo shows, the distal half of her bill is bent upwards at a 45 degree angle. We were alarmed at her situation, which appeared uncomfortable, at least, and deadly, at worst.

But she behaved normally. Since we carefully observe, painstakingly describe, and publish articles about loon behavior, we habitually assess any loon’s comportment that we see according to thousands of others seen before. Her diving and foraging was normal. Far from permitting too-close approach by humans — a common red flag that can indicate severe injury — she was actually rather skittish. She pointedly moved away from us whenever we approached in an effort to look for leg bands.

Anatomically, she is far from normal. Bird’s bills consist of a matrix of bony support, covered by a keratinized epidermal layer (rhamphotheca). In other words, the displaced part of this loon’s bill should comprise not merely soft tissue but bone. Mark Pokras, associate professor emeritus at Tufts School of Veterinary Medicine, assures me that the fact that the bony foundation that should extend to the bill tip is missing means that it “will never grow back normally”. The best we can hope for, he says, is that the bent keratinized tissue — all that remains of the end of her upper mandible — drops off eventually. I was chagrined to hear this news but heartened to learn also that Dr. Pokras has, during his decades of loon anatomical study, seen about 10 cases where large portions of loon bills have been missing. These cases include a male in Maine that had only half of an upper mandible (as this female does) but that fed itself normally, held its territory, and produced offspring in multiple years.

That loons can survive an injury of this kind to a crucial feeding organ and still breed seems remarkable. I suppose their resilience might be explained partly by the  challenges they face routinely across the range of different landscapes they inhabit. That is, an animal that must locate, pursue, and capture a broad spectrum of actively-swimming prey — in water that is sometimes fresh, sometimes salty; sometimes clear, sometimes turbid, must be a flexible and adaptable creature indeed.

We all focus most of our attention on breeding pairs and their chicks. Why not? Breeders are the loons we get to know — day after day, year after year — as they struggle to hold their territories, choose nest sites safe from raccoons, incubate their eggs for 4 long weeks, and then protect helpless offspring from all manner of environmental threats. We admire the toil and turmoil they face each year and are downcast when they lose their breeding position, nest, or chick. And we grieve when they die. I am probably unusual in this regard, but I am also inspired by observing the challenges that breeding pairs routinely confront and overcome.

In our obsession with breeding individuals, though, we forget about the many loons living on the margins. These are “floaters” — mostly 2 to 7-year olds who spend the entire summer without a fixed home. Floaters are the individuals that forage alone on small lakes or skulk along the outskirts of defended territories, occasionally socializing with or accosting territory holders. Unlike territorial loons, they drift about.

Although their lives might seem simpler and less stressful than those of territorial loons, floaters — even young ones — face challenges of their own. Our work has shown that 2- to 4-year olds are much lighter than 5- to 7-year olds, are more submissive to territory holders during territorial intrusions, and almost never initiate battles for territorial ownership. Yet these youngsters do intrude into breeding territories. We presume, therefore, that even as they mature, young floaters collect information about owners. Our data show that young floaters intrude strategically into territories within a focused area (usually about 10km in diameter, see figure below from our recent paper) so as to meet and interact with owners of their own sex that they might

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evict down the road.

Having reached optimal adult condition, floaters of 5+ years of age begin to size up owners with greater urgency, choosing to battle those that appear weak or are noticeably weaker than they were on a previous visit. Male floaters probably also listen to the quality of a male owner’s yodel, because certain acoustic elements of the yodel convey information about the yodeller’s body size and condition. As we have seen repeatedly, intrusions by floaters of 5+ years of age are not welcomed by territory holders — and can be dangerous for both parties.

Considering that 2 to 4 year-olds are still reaching optimal body condition and 5 to 7 year olds are putting themselves at risk by actively seeking territories, it is surprising that floaters of both age groups survive at a rate just as high (about 90% annually) as established pair members (see figure below). Apparently the risks of probing and competing for a territory among young loons are roughly equivalent to those that come with

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territory defense and chick-rearing among older individuals. (Note from the figure that only older age-classes, and only males, show lower survival.)

We are used to the invisibility of floaters. That is, we see and study them as intruders into defended territories, but we seldom consider where they come from or how they live. So I always get a jolt when a dead floater turns up, like the tame 5 year-old male in Linda’s photo from the Lake Nokomis area. These rare unpleasant finds are a good reminder that gaining a territory is a long and difficult slog.

 

Since snow and ice lingered far too long this spring, loons were late to nest in northern Wisconsin. The lateness of the season has also reduced opportunities to renest after early nest failures. There was simply limited time for pairs to weather four weeks of incubation and still rear the chicks to a point where they could learn to fend for themselves and make their way to Florida. Add to the narrow window this year the mishaps that cost us young chicks on several territories….and I was beginning to sweat.

But my fears of another off-year for nesting success in the Upper Midwest loon population have not been realized. A relatively short period of black fly abundance has helped immensely. As our recent paper showed, abandonments from black fly harassment are a good predictor of nesting success; that pattern has continued in 2018. So it seems likely that this year will break our four-year breeding slump.

Here are the numbers. As of July 4th, we had an estimated 48 breeding pairs in our study area with a chick or chicks. Eighteen (give or take a few) were still on nests, of which over half will produce chicks also. That leaves us with roughly 60 loon pairs with chicks. A handful of the 60 pairs will lose their chicks before 8 weeks; in addition, though, we will make roving visits to non-study lakes within and just outside the study area and find about 6-8 more pairs with chicks. When the dust has settled, we should end up with a number of pairs with chicks that is very close to the 65 successful breeding pairs we were able to band in 2013. That fact is worthy of note, because 2013 was both a year in which our procedures and lake coverage were similar to this year, and the last solid year of breeding. So we can all breathe a great sigh of relief — and enjoy Linda’s cool photo of the freshly-hatched chick on Muskellunge Lake and the female, with moist eggshell fragments still adhering to her breast.

As of today, 32 of our territorial pairs have hatched chicks. We are on pace with last year, despite the three-week delay in nesting resulting from the cold winter. I am encouraged; 2018 looks to be at least an average year for chick production.

My optimism about the breeding season has been tempered of late, as we have gotten fresh evidence of the frailty of newly-hatched chicks. In the past two weeks, four pairs with tiny chicks have lost them — a higher than average rate of loss. Linda first reported that the chick on her lake suddenly disappeared; her observations suggest that a snapping turtle might be the culprit. Yesterday, the chick on Crystal Lake (Lincoln County) fell victim to the attack of an intruding loon, as reported by a lake resident. And two northerly pairs — on Blue-Southeast and Carrol — also completed four weeks of incubation only to lose their chicks in the first few days after hatching. The causes of chick loss are unknown in these two cases.

Loss of chicks in the first two weeks of life is not terribly surprising. Young chicks must confront a great many challenges, including simply keeping themselves warm and avoiding physical injury as they learn to swim and move about. But the greatest hazards to hatchlings, we have learned, are strictly biological. Being tiny, having limited mobility, and with only a vague sense of the dangers posed by much larger organisms in their habitat, young chicks can be attacked and killed by a wide variety of animals — intruding loons, snapping turtles, muskies, and eagles, to name a few. In contrast, adult loons are wary, agile, and large enough that the list of potential attackers is short. Adults have simply outgrown much of the danger from other living things in their environment.

As discouraging as it is, I am convinced that this recent spate of chick deaths is a statistical blip. There has been no sudden change in the loons’ habitat, or explosion in the population of any predator, that could signal the beginning of a worrisome trend. Rather, this is just an unfortunate negative swing that will be washed out by later swings, negative and positive, and ultimately forgotten. Perhaps we can hurry the process along by focusing on Linda’s recent photo of the female (“Honey”) and chick on Muskellunge Lake.

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.

 

Most of us have been there: determined to take the next step in life but thwarted in our efforts to do so. More often than not, another individual occupies the position we seek. That is the situation in which nine year-old W/G,B/S (hereafter “White-Green”), finds herself on Blue Lake.

Blue seems a good fit for White-Green. She grew up on Franklin Lake in Forest County, another large, clear-water lake 35 miles to the northeast. Since young males and females try to settle on breeding lakes similar to their natal ones, it is natural that White-Green should try to find a place on Blue.

But setting your sights on a goal and achieving it are two different things. Back in 2014, when she was only five years old, White-Green battled with the 15 year-old female from the Blue-West territory and lost. Since then, she has made sporadic attempts to evict her decade-older rival, failing each time. In 2016, she observed the violent overthrow of the male at Blue-Southeast by a younger rival. However, the carnage that ensued offered White-Green no opening at a breeding position at Blue-Southeast, although she paired briefly with the male evicted from that territory. Since then, we have so often seen White-Green on Blue Lake – and never on adjacent lakes that we also monitor — that she must live there, hiding out in the swath of unoccupied space between the two breeding pairs. And waiting.

She waits still. Two weeks ago, White-Green again challenged the Blue-West female, in what has become an annual ritual. I have begun to feel frustrated on White-Green’s behalf. Her many fruitless attempts at usurping a space recall times when I myself have been baffled in a crucial life pursuit. It would seem that the writing is on the wall: White-Green is not strong enough to subdue the breeding female at either end of the lake and seize their breeding position. Shouldn’t she move on? Isn’t she wasting valuable time in the prime of her life? As a biologist, I come at this from another angle, asking, “Could White-Green’s obsession with acquiring a territory on Blue Lake be evolutionarily advantageous?”

A precise answer to this question would require a calculation of evolutionary fitness benefits of fighting for a known resource versus turning her attention to a new target — a neighboring territory on Bobcat, Bolger, or Kawaguesaga. We do not have sufficient data to make such a quantitative comparison. However, White-Green’s “siege” of the Blue-West territory does highlight two quirky features of the loon breeding system that might help us understand her odd behavior.

Whether male or female, nonbreeding loons in search of a territory set their sights on a handful of them that they visit often, rather than casting a wide net that includes dozens of potential territories. We infer from the narrow scope of their search that young nonbreeders might use a strategy of sizing up territory owners, monitoring their condition regularly, and challenging them for ownership when they seem most vulnerable. (Of course, nonbreeders would prefer the low stress alternative of replacing a breeder that has died.) The tradeoffs of focusing on a small number of territories are clear. By getting to know the behavior of a few breeders well, young nonbreeders might be able to pick up subtle changes in breeder behavior that signal weakness and allow them to time their eviction attempts effectively. And conducting a narrow search might also permit a nonbreeder to learn about the illness or death of a territory owner rapidly, so that they can quickly mount a bid for the territory and claim it before others learn of the opportunity.

Another quirk of the loon breeding system is a female-biased sex ratio caused by greater longevity among females. That is, there are always more breeding females than breeding males in the population, since many males die young. The longer lives of females is a double-edged sword from their standpoint. On the one hand, there is vigorous competition for any female breeding vacancy that becomes available. On the other hand, females live long enough that what at first appears to be an unhealthy obsession with one territory or two might ultimately be rewarded.

Breeding prospects for loons in northern Wisconsin seemed dim only three weeks ago. Not only had a frigid April delayed the start of nesting, but Simulium annulus was doing its best to keep loons from warming the eggs that had taken so long to appear. A statistical correlation between cold spring temperatures and black fly harassment had me fearing that the long-awaited nests would be abandoned in short order – delaying the season still further. My hopes for a bounce-back year of breeding, after 2017’s disappointment, seemed distant.

As I keep learning in life, unfathomably horrid situations often improve. So it was this spring. To be sure, loons were forced to abandon a few early nests – those at Langley, Fox, and Wind Pudding-East, for example – owing to fly harassment. But loon pairs that had been reluctant incubators in mid-May suddenly bent to the task late in the month. Even after accounting for the inevitable wolfing down of eggs in exposed nests – such as those at Two Sisters-Far East, Long, and Little Bearskin — by raccoons and their ilk, the vast majority of our breeders are sitting on eggs (like the male on Linda’s lake; see photo). At last count, 79 of 123 pairs we cover are on nests that have survived the crucial first ten days. Two weeks or more of incubation remain for most of these territories. But barring some unforeseen disaster, 2018 might be one of the most productive years for northern Wisconsin loons in the last quarter century. Who would have guessed that a breeding season that started so inauspiciously would gain such momentum?