A week or so ago I gave a talk to the Northeast Loon Study Working Group. Inauspiciously-named and -initialled, NELSWG comprises loon conservationists from New England, the Upper Midwest, and a smattering of other regions within the loon’s breeding range. At present, NELSWG is the only group that attempts to pull together data on loon populations and brainstorm strategies for protecting the species. During my talk I shared our data showing that masses of adult loons and chicks decline as water clarity declines. I then updated the group on my analysis of male and female traits that lead to breeding success of pairs.
To remind you, a male’s knowledge of the territory makes a huge impact on the breeding success of a pair. Since males choose the nest location, males are a drag on nesting success in their first few years on a territory because they place the nest in lots of dangerous places. (Note the low blue bars for years 0 to 3 above.) On the other hand, males that have been on a territory for seven or more years are a boon to pair nesting success, because they have learned the safest spots to place nests. (Note the blue bars from 8 to 20 years on territory.) Females have an impact too. In their first year on a territory, females cause low hatching success for their pair. In later years, female territory experience boosts hatching success slightly.
It is almost more interesting to see the factors that do not affect breeding success. A male’s age does not affect his pair’s ability to fledge chicks at all. At first glance, this seems confusing. How can the male’s age have no positive impact on breeding success of a pair, when a male’s breeding experience on a territory is hugely important? The answer relates to cause. It is true that old males tend to have very high breeding success, but this is not because of their age but because, in most cases, they have been on a territory for many years. We know that age itself is not causing high breeding success because old males that nest on new territories have no greater breeding success than young males on new territories. It is familiarity with the territory and not age that is the salient factor.
Female age has only a weak negative impact on breeding success. In other words, older females lose chicks at a slightly higher rate than young females. This pattern is a bit difficult to make sense of, because the effect is so steady and gradual. Why would a 15-year-old female lose chicks at a higher rate than a 10-year-old female parent? Both females are in the prime of life, in the loon sense.
To the listeners at NELSWG, though, the pattern that was most remarkable was the lack of a strong effect of mate familiarity. While pairs that know each other nest a few days earlier than pairs that are in their first year together, the pattern is weak (see below). Furthermore, the slightly earlier hatch date among pairs that know each other does not translate into a detectable advantage in overall breeding success. In short, pairs benefit only slightly from knowing their mate well.
How can this be? How can a male and female remain together year after year, raise young cooperatively — and still not benefit from this lengthy association? That was the question asked by Lee Attix at the NELSWG meeting. I don’t have a good answer for Lee. As a male in a 38-year relationship who has raised young cooperatively, I am well aware of the benefits that a long-term partnership can bring in the human species. But loons are different.
I should have known all along. I should have known last May, when the ancient outboard motor we had just bought to cover the Whitefish Chain spewed a foul rainbow sheen onto the water’s surface and belched a caustic purple cloud that momentarily blinded us. I should have known as I filled huge tanks of gasoline at the Holiday convenience store in Crosslake, hefted them down to the dock, and hooked them up to the belching motor. I should have balked at the absurdity of using a filthy, fossil-fuel-guzzling outboard to study an animal that requires clean air and water.
Instead, I shrugged. “This is how people get around in the Northwoods”, I thought. “This is inevitable. This is the environmental cost of studying loons on big lakes.”
In my own defense, my understanding of proper boating practices became ingrained during my childhood. Back then, when we needed to provision our cottage on an island on 40-mile-long Lake Temagami in central Ontario, we took our little 2-stroke outboard over to the Ojibway Store on Devil’s Island. I still recall taking in the pleasing aroma of balsam fir mingled with mixed gasoline as we listened to the soft lapping of waves against the store’s dock. At the time, my major concern was whether Mom would treat us to Burnt Almond bars when she had finished ordering our groceries. Gasoline was just an innocuous part of the landscape we inhabited.
Indeed, to folks of my generation and generations adjacent, the angry whine of an outboard motor, the slap of a stiff wind in our faces, and the sight of parting, churning waters behind us seem inextricably linked to the pungent smell of gasoline.
But it need not be so. There is a growing market for electric outboards (and inboards) that can replace gasoline motors smoothly and are far cleaner (of course), quieter, and — according to what experts say — very reliable and low-maintenance. I have been researching this.
Why have I experienced this sudden desire to go electric on the water? Two reasons. First, the last two Wisconsin field teams and I faced an absolute nightmare every time we tried to start up our vintage 9-horsepower Evinrude. I did not collect data on our efforts, but I believe we averaged 43 almost-shoulder-dislocating tugs of the starter cord per lake to get that dirty old 2-stroke started. I have had it! (I believe Sarah ’22, Molly, Claudia, Chris, Tia, Bailee, and Sarah ’21 will applaud this move.)
Second, I can no longer deny the obvious. The relentless march of climate change has begun to hurt loons in the Upper Midwest. We can see it in the increase in the May black fly population, which forces loon pairs to suffer horribly as they to incubate their eggs, often to the point of abandonment. And it is even more evident in the sharp decline in July water clarity during the past quarter century (see below) — a decline that impairs loon parents’ ability to find food to feed their chicks. Both increased black flies and decreased water clarity, we now know, come about in large part because today’s warmer, rainier summers produce more flowing water that: 1) supports increased black fly reproduction and 2) washes more matter into lakes that reduces clarity.
So I have finally figured something out that I should have guessed before. Climate change is hurting loon populations in the Upper Midwest in multiple, measurable ways. Cutting back on fossil fuel usage where I can will help slow this damaging pattern. And that is a step in the right direction.
The past month and a half have been a roller coaster ride, though mostly downwards. Six weeks ago I learned that major funding for my field work in Minnesota had dried up. I cursed my luck. I scratched my head. A thousand “what ifs” passed through my brain.
But looking back was pointless. In time, my mind began to turn to one cheerful and unassailable fact. Loon Project field teams in 2021 and 2022 had given their all to expand our database into a new state where, initially, we knew almost no one. As we began to meet the warm, supportive, loon-loving folks of Minnesota, we gained momentum. The National Loon Center provided tons of support, financial and logistical. New friends shared boats, gave us access to private lakes, towed our capture boat from lake to lake in the middle of the night, or simply drove us around in their own boats during capture to help us find and mark breeding loon pairs. Kevin Kenow and his USGS colleagues spent six long nights in 2022 capturing loons to swell our study population. When the dust settled in early August of last year, we were well over halfway to our goal of establishing a Minnesota Study Area on par with our traditional study area in Wisconsin.
That we have not been diverted from that path is a tribute to our great pool of friends and supporters in Wisconsin, Minnesota, and across the U.S. One day a few weeks ago was a first turning point. An anonymous friend from Wisconsin pledged $7,000 “to support the Minnesota part of the Loon Project”. I was touched that someone in Wisconsin trusted me with this gift, and moreover, dedicated it not to the loons of their own state but to those of an adjacent one. *
Just yesterday, another group of donors from Minnesota helped us reach another turning point. Roger and Phyllis Sherman, Don Salisbury, and Gwen Myers have together contributed $21,000 to the Minnesota Loon Project to establish the Judith W. McIntyre Fund to support our work in the state.
It is a great honor to feel that I am building upon Dr. McIntyre’s seminal work on loons, which took place in Minnesota, Saskatchewan, and Upstate New York. Judy had a gift. She did robust, impactful science that taught us a great deal about loons. At the same time, she was able to convey her passion for loons and loon conservation in a charming, down-to-earth manner that reached the public. I have a dog-eared copy of her classic book, “The Common Loon: Spirit of Northern Lakes” on my shelf to which I often refer. When I think back to my interactions with Judy, though, what I remember most vividly is the warmth and humility with which she welcomed me to the fellowship of loon biologists back in the mid-1990s. She viewed the study of loons as a calling to which all could aspire — even the young whippersnapper that I then was.
The new Judith W. McIntyre Fund is a timely and exciting development. This gift adds to the dozens from other supporters of the Loon Project from Alaska to Colorado to Maine who have stepped up to donate during our time of greatest need. And I cannot forget other folks who have provided the Loon Project team with lodging in Wisconsin (especially Skip and Ruby, Mary, and Linda and Kevin) and Minnesota. Friends and supporters have truly kept the Loon Project afloat in recent years. Gifts earmarked for Minnesota have now brought us right back to where we were before the loss of funding six weeks ago. In other words, thanks to all of you, our goal of producing a robust population model for loons in north-central Minnesota is back on the horizon.
I know what you are thinking: another feel-good story of overcoming adversity that features loon/human parallels! Now that we are back in business in Minnesota, perhaps I will plague you less often with such tedious anecdotes. But things have been going pretty well lately. So I can’t make any promises.
* As I noted in an earlier post, research in our traditional Wisconsin Study Area will proceed as before. That is, we will continue to build the Minnesota Study Area without compromising our productive long-term study of loons in Wisconsin.
After losing our primary source of funding for Minnesota, we are facing a money crunch. The news came rather suddenly. It has left me pondering this sea change in our circumstances and wondering where it leaves us.
It is ironic to lose our funding at this particular moment. After intensive field efforts in 2021 and 2022, the Chapman/Loon Project database now contains two full years of field data from Minnesota. We have made scores of friends and lake contacts — mostly through the tireless efforts of students on the LP field team in Minnesota. Having marked one or both adults on 57 of 105 territories we cover in and around Crosslake, we are more than halfway to our goal of building out the Minnesota Study Area. Completion of our marking efforts in 2023 and 2024 would bring Minnesota up to par with our long-term study population in Wisconsin. Most important, we have roughly half of the necessary data to construct the first-ever true population model in the state using marked loons. So it is only a slight exaggeration to say that we have accomplished in two years in Minnesota what it took us 10 to 15 years to achieve in Wisconsin.
In short, our 2021 and 2022 field teams in Minnesota have built a great LP database that has all of the promise we thought it would. I would be remiss if I did not thank Kevin and the USGS loon capture team that contributed mightily to our banding efforts in 2022. A bunch of other folks helped out with capture and tracking of the Minnesota population in 2021 and 2022, including Mike and Natasha of the NLC, Richard and Terri, Dawn and Keith, Mary, and Kris. Jon, Melanie, and Mike from Boyd Lodge housed the field team during our work. Mike and John loaned us their boats. (Apologies if I have forgotten someone.)
Naturally, now that we have established a robust study population from which we will soon be able to extract reliable population data, I am acutely concerned about the sudden funding shortfall. But should you share my concern? If you live in Wisconsin or Maine or Ontario, why should you care about Minnesota loons? After all, we have excellent long-term data on the northern Wisconsin loon population that provides a sensitive gauge of the population trend in one part of the Upper Midwest. Why can’t we generalize the results from Wisconsin to Minnesota? In other words, if the Wisconsin loon population is thriving or tanking, isn’t it safe to presume that the Minnesota population is doing the same?
Minnesota and Wisconsin loon populations certainly seem similar. The states share a lengthy border across which loons fly freely. We have learned from recoveries of our banded birds in other seasons that the migration and wintering grounds of Wisconsin and Minnesota loons overlap almost completely. Adult loons in Wisconsin and Minnesota are of very similar size — and both populations contain adults much smaller than the loons of New England. Loons consume the same species of fish, are plagued by the same species of black fly, and must dive, duck, and dodge boats and fishing lures in both states. Importantly, lead fishing tackle — banned in New England — kills many adults and chicks in Wisconsin and Minnesota both. And, of course, loons are also loved and fiercely protected by most lake residents and visitors in Minnesota and Wisconsin. Doesn’t all of this mean that the population trend we detect in Wisconsin loons is likely to hold also in Minnesota?
Perhaps. But there are also differences. In general, loons appear to be packed more densely in Minnesota than in Wisconsin. Weather patterns, while broadly overlapping, differ between the states. Minnesota loons are more northerly, on average, than loons in Wisconsin. To presume that the two states’ loon populations fluctuate in harmony is risky. And, of course, if the Minnesota loon population echoes the Wisconsin loon population, our Minnesota measurements are even more important to make. Remember, the northern Wisconsin loon population is in serious decline. Minnesota loons could be declining in concert with Wisconsin loons, could be stable, or could be declining more rapidly than Wisconsin’s loons. Without running the numbers, we just don’t know.
The condition of Minnesota loons matters for another reason. Since loons in the Upper Midwest experience many of the same hazards as loons across the breeding range (e.g. water clarity, black flies, human angling, lead toxicity, and recreational pressure), our detailed and rigorous observations in Wisconsin and Minnesota have implications far beyond the Upper Midwest. By studying two populations 200 miles apart, we can compare factors that impinge on loons across populations. Any common patterns that we see across the two study populations are likely to indicate factors of broad impact — factors probably important in New Hampshire, Quebec, and Montana.
My discussion of the Minnesota loon population exposes a second irony. Minnesota provides a summer home for more loons — by a 3 to 1 margin — than any state in the lower 48, and Minnesotans love their state bird. Yet Minnesota arguably knows less about its loons than any other state in the contiguous U.S. (As I pointed out some months ago, what data we do have on Minnesota loons create cause for concern.) The LP database in Minnesota — once we finish building it and can build a model to learn about population dynamics — would permit us to remedy this unfortunate irony regarding Minnesota’s loons. Our work would alert us to any decline in the state, and our accompanying study of causes of reproductive failure could help us design and put in place a conservation plan that (with luck) could reverse any decline. Yet with this crucial milestone in sight, we suddenly lack the funding we need to reach it.
In truth, we have always faced challenges in Minnesota. Our most important lake there is Whitefish, which contains about a third of our territories, and where we are sometimes driven off of the lake by brutal winds and whitecaps. Even our “small lakes” in Minnesota are, on average, 50% larger than those in Wisconsin, which forces us to spend longer periods finding study animals by canoe. When compared with Wisconsin, everything is expensive around Crosslake and often in short supply — that goes for lodging, storage space, equipment, and most everything else. And tacking a Minnesota Study Area onto the Wisconsin Study Area has doubled my annual workload. Despite my determined efforts, I have not spent enough time in Minnesota nor have I been able to adequately support the field team there. Considering the 1,329 obstacles we confront in Minnesota — to which we can now add lack of funding — maybe we should throw up our hands and throw in the towel.
But then, loons could say the same. Territorial pairs face enormous obstacles each summer in trying to raise chicks. They must find safe nesting sites, defend them from predators, and incubate their eggs for four long weeks regardless of weather conditions. Hatching, which would appear worthy of a celebration, is, in reality, not even a halfway point for the pair. Instead, hatching merely introduces a new suite of hazards for parents, including new predators, the threat of infanticide by intruding loons, and the difficulty of finding enough food for their chicks — especially if they are on a small lake and it has been a rainy summer. And, of course, both parents are in constant danger of being evicted from their territory by young upstart loons that are always on the prowl for breeding territories. In short, the task of raising two healthy chicks, or even one, is incredibly daunting. If loons had the ability to ponder the vast array of obstacles to successful reproduction, they might never attempt it.
The desperate struggle of loons to raise young despite a host of challenges was illustrated vividly by the loon pair on the Little Pine-Dream Island territory this year. Little Pine is a pleasant, rather quiet lake on the Whitefish Chain. We marked the Dream Island pair in 2021, during which they raised a chick. Both pair members returned this year, so we knew they were veterans with a track record of chick production. But their experience in earlier years did not prepare them for the buzzsaw they encountered this past summer. When we found the Dream Island pair on May 27th, they were off the nest and spending a great deal of time under water. We quickly learned why. Black flies were tormenting them mercilessly. The relentless flies were present in huge numbers on the nest and on vegetation near the nest. They frolicked in great clouds in the air above the nest. And the pair members’ heads were blanketed by flies, each probing the skin for a spot to make an incision. Even constant diving by both male and female failed to dislodge these blood-sucking pests. During our visit, the male (pictured below in the water near the nest) made a pitiful attempt to mount the nest and resume incubation, but he could not bear to do so.
After surveying the nightmare scenario at Dream Island, I gave them a low probability of resuming their incubation duties in time to rescue the eggs and hatch their chicks. It did not seem possible that a male and female whose heads and necks were thickly encrusted with welts from hundreds upon hundreds of fly bites would see this nesting attempt through to hatching. But by some miracle, the pair hatched both eggs successfully three weeks later. I was flabbergasted. Despite 30 years spent watching nesting behavior of loons, this one successful attempt against all odds remains seared into my brain. It is impossible to know how many female black flies participated in the blood-letting of the Dream Island pair. But I suspect, like us, they had at least 1,329 reasons to quit.
I find myself drawing inspiration from the Dream Island pair. No one could have anticipated that they would hatch their eggs after facing such an unexpected and disheartening challenge. Yet offered the temptation of bowing to adversity, they stuck it out and triumphed.
Field ecologists are often told that they come to resemble their study animal. I am not dismayed by this comparison. In fact, if I can bring half as much determination and stick-to-it-iveness to my research program as the Dream Island pair bring to their nesting efforts, I will consider myself an unalloyed success.
This seems a good time for me to emulate the Dream Island loons and resist the temptation to give up the Minnesota work. The stakes are enormous. Minnesotans would be devastated to lose loons from the state or even from part of the state. And based on my work in neighboring Wisconsin, Minnesota loons are likely in trouble. Do I turn away from these good people — and a new set of loons with which I have begun to bond — when I meet some adversity?
So I am asking for your help. If we are able to raise $3,500, that will permit us to go to Crosslake and complete the late May census of the 105 or so loon territories that comprise our study area there. The census is a vital part of the year’s field effort, because sightings (or non-sightings) of adults we marked in 2021 and 2022 permit us to calculate the rate of return to the territory from the previous year, an indication of adult survival. If we are even more fortunate and receive $7,000 in donations for the 2023 Minnesota field effort, that will allow us to complete the all-important May census and also visit the territories again once or twice in July to determine rate of reproductive success. Reproductive success is a second important piece of demographic data that will help us refine the population model we build in two years. Finally, if by some miracle we are able to pull together $17,000 for Minnesota, that will permit us to do the census, measure reproductive success late in the year, and band enough new loons to bring our Minnesota Study Area up from two-thirds finished to fully marked. The 2023 banding effort would increase our sample of banded birds and strengthen the population assessment we will carry out in the near future.
If you have already donated to our study, thank you so much! If you have not yet contributed financially to our work and are now able to assist with our Minnesota field effort, we would appreciate it! As I have explained, your donation will be spent in an effort to learn about and conserve Minnesota loons. (If you wish to donate funds, but would like your donation to go to helping loons in our traditional Wisconsin population instead of the new Minnesota population, please specify that when you donate, and we will honor your request.)
Feel free to e-mail me at email@example.com if you have questions about our fundraising effort and how you can help. For example, if you can offer us housing in the Crosslake area for a week in May and/or for ten days to two weeks in late July, that would reduce our funding needs greatly and bring us closer to our goals.
Thanks for any help you can give us. I am anxious to complete the promising work that we began two years ago and will move heaven and earth to keep the Minnesota Study Area afloat. Things look grim at the moment, but I am hopeful that, like the Dream Island pair, I can weather adversity and emerge stronger on the far side of it.
An association between loons and water clarity seems reasonable. After all, loons are visual predators. Why would they spend time in water through which they cannot see?
Yet I learned in Wisconsin in the mid 1990s that loons do not strongly favor clear water. While many of my study lakes, like Alva and Two Sisters, are quite clear and produce chicks regularly, many others, such as Hancock and Oneida, are both turbid and productive. In short, loons in the Upper Midwest thrive and fledge chicks on lakes that vary between 3 and 20 feet of visibility. Indeed a scientific analysis showed that water clarity is not among the factors that dictates use of a lake by loons.
If you think about it, you can understand why a migratory species like the common loon does not overspecialize on water of a certain clarity. As we know from Kevin Kenow’s work, loons fly hundreds of miles across largely unknown terrain and then must land on a waterbody somewhere. If they are in desperate need of a meal at such times — as we might presume — they had better not be too finicky about the menu and the eating conditions. Flexibility must be especially important among juveniles migrating south for the first time, who are crossing terrain that is entirely unfamiliar to them and must find food nevertheless. And, of course, migration begins or ends in the Gulf of Mexico or Atlantic, where both diet and water clarity are entirely different from that during the summer months.
Just to be very plain here, I am saying that short-term water clarity (during the month of capture) increases loon masses because they probably see their food more easily, but some factor related to long-term clarity (how clear the water is on average, over many years) actually makes it harder for loons to put on mass. How do we make sense of this brain-twister?
We can only speculate about the long-term water-clarity-related factor that hinders loons’ foraging. However, there is a prime suspect. Human recreation is strongly correlated with lake water clarity. In other words, people like to spend time boating, fishing, and swimming in clear lakes. During the time when loon parents are trying to stuff their chicks with food, we humans are out there complicating the process by frolicking about in their vicinity. It seems quite plausible that this burst of human activity causes loons to lose precious foraging time and perhaps also access to their favorite foraging spot, if humans are using it. So we can easily see how human activity might cost loons some food and thus reduce mass.
If I am correct that humans impair loon foraging in clear lakes, then we can count breeding on a clear lake as a mixed blessing for loons. Clear water makes food easy to see and catch, but it brings hordes of humans that loons and their young must avoid — which cancels out a good deal of this advantage. Now, if a loon pair were to breed on a lake that had clear water and was inaccessible to humans, they would have it made! Sadly, this seldom happens in our neck of the woods.
In addition to this cool but somewhat distressing news about loon biology, I have distressing and not at all cool news about the Loon Project. We have just lost our primary funding source and are therefore going to be a bit tight for 2023 and perhaps beyond. I am hoping to use a “rainy day fund” to make it through 2023 in Wisconsin. Continuation of the work in Minnesota, which we began only two years ago, is now very much in doubt. If you can consider a donation to help us fight through this lean period — so that we can continue to learn about loon biology in ways that might help preserve the Upper Midwest loon population — we would really appreciate it.
Ensconced as I am in the endless summer of southern California, it is easy for me to forget what loons are facing. As we know from Kevin Kenow’s excellent work, about half of all adults have now left their breeding lakes in Minnesota and Wisconsin and are on their way southwards. Many of these birds are hanging out in the Great Lakes before making the long overland journey to Florida. Some adults remain faithfully with their chicks, hoping to stuff a few extra fish into them before abandoning them to their own devices.
Adults’ departure leaves only chicks on the breeding grounds. Thanks to the the work of our fall observation teams and Brian Hoover, who pulled the data together and wrote it up, we know that most juveniles leave their natal lakes in the fall but hang out nearby. They search diligently for large, food-rich lakes, especially favoring those that resemble their natal one in pH. Their strategy is clear. First, stuff your face with fish where they are abundant and similar to the ones you first learned to hunt. Next, wait until the last possible minute to build up your energy stores. Finally, bolt for Florida before the ice makes it impossible to take off.
The juveniles’ plan has a touching pragmatism to it. There is no subtlety. Birds of the year are not burdened with territorial responsibilities or pangs of parental guilt. They just wish to survive long enough to reach the wintering grounds. And, generally speaking, they do.
But a few get left behind. Thus it happened with the Lake Thompson juvenile this fall. A great strapping youngster when we caught him in late July at five weeks of age, he continued to grow and thrive in the 12 weeks since we last saw him. Ultimately, he had no more need of his parents and moved five miles west to Boom Lake in Rhinelander to fatten up for migration. There, however, he ran afoul of a reckless hunter. Linda and Kevin Grenzer caught him last night and quickly saw that his left wing was fractured. X-rays at REGI confirmed the break — caused by goose shot visible in the x-ray.
If you feel as though you haven’t heard from me in awhile, it is because I’ve been in the weeds. But my time in the weeds has been fruitful.
I have been analyzing loon reproductive patterns. Specifically, I am investigating what about adult loons themselves and their surroundings leads to success in hatching their eggs. The trove of detailed breeding data we have — 100+ territories followed closely for almost 30 years — gives us a unique window onto predictors of hatching success. I gave a hint of this analysis some months ago. But more data and a refinement of earlier statistics have clarified our understanding and led to new findings.
One of these findings might be familiar. Males, which choose the nest location, improve in hatching success as their familiarity with a territory grows. This is easy to understand. They use trial and error to find a good nest location. During the first few years on a new territory, they blunder about and lose many nests to predators. Over time, they improve their hatching success by avoiding sites where predators took the eggs. As the predictive curve shows, males make rapid progress in their first year or two on a new territory. Once three to four years have passed, their year-to-year improvement is small.
However, males continue to show incremental — but statistically significant — improvement in hatching success from year to year, even after 15 years on the same territory. Although the annual improvement is slight, it adds up. For example, a male with 20 years on a territory has a 27% better chance of hatching his eggs than a male in his second year. It’s a little hard to imagine the reason for this sustained improvement. Does a male only notice certain biological aspects of his breeding territory through prolonged exposure to them? For example, might a male observe over the course of many years that mammalian shoreline activity is higher at the south end of the lake than the north end and avoid placing a nest at the south end if — say, in his 17th year — circumstances should force him to relocate it? Maybe. In any event, the finding is exciting for the study of animals generally. It suggests that, for an intelligent animal inhabiting a spatially complex territory, adaptive learning — that is, learning that increases reproductive fitness — never really ends.
What about females? Like males, females improve in hatching success over time, but the pattern is completely different. Females have low hatching success in their first year on a territory but improve markedly in their second year. However, they do not continue to improve. Hatching success for females “tops out” after their second year on a territory. The female improvement pattern seems less difficult to explain than the male pattern. Since females do not control nest placement, they do not have any obvious means to get better at hatching eggs as males do. But they must learn something vital about the territory in that first year in order to enjoy greater hatching success in all other years. Perhaps they quickly learn where to forage in that first crucial year and retain that knowledge from the second year on. If so, that important knowledge might allow them to nest more often or better sustain the incubation effort.
Comparison of the two figures shows the contrast between males’ steady improvement in hatching success over their entire residency on a territory and females’ one-time jump up to higher hatching success after their initial year.
How can we be sure that the effects I have described are attributable to females’ and males’ experience on a territory instead of merely age? It seems reasonable to hypothesize that adult loons might get better at hatching eggs simply as they gain experience with nesting, regardless of the territory they are on. But this is not the case. I included age as a variable in the statistical analysis, and age turned out to be a poor predictor of hatching success. Thus, a 29-year-old male who loses his territory and settles with a new female on a new territory is right back to square one. He must learn again by trial and error on the new territory where to nest and where not to nest. He is no better off than a five-year-old male that has just settled on his first territory.
What about duration of the pair bond? Since males and females both incubate the eggs equally, they must coordinate their incubation schedules in order to hatch the eggs. So one might have expected that many years of breeding together would translate into greater hatching success for a male and female. But I included duration of the pair bond as a variable in the statistical analysis. Like age, pair bond duration is inconsequential. Yes, males and females that have been together for many years tend to hatch their eggs more successfully than new pairs, but they do so because: 1) the female is past her first difficult year of low hatching success, and 2) the male continues to improve his nest placement over many years on a familiar territory.
Why do I spend so much time making what must seem like fine distinctions? Does it really matter whether old males and females hatch a lot of chicks because they are old or because of experience on a territory? Who cares that old males and females hatch more young not because of more time spent together but because each of them has gained experience with a territory asindividuals? We should all care. Since territory familiarity, not age or pair-bond duration, confers reproductive ability upon adult males and females, we should redouble our efforts to ensure not merely that loons themselves live long lives, but that we minimize disturbance to the familiar nesting areas on which their breeding success depends.
Beautiful photo of Clune sitting on his nest by Linda Grenzer.
The pattern is stark. As you can see from the graph below, loon pairs using artificial nesting platforms have produced a much higher rate of fledged chicks in the Wisconsin Study Area than in the Minnesota Study Area. The pattern was especially dramatic in 2021, when Wisconsin platform pairs reared twice as many chicks per platform as Minnesota pairs. But to compare study areas on the basis of a single year is unwise. Moreover, 2021 was a dreadful year for black flies in north-central Minnesota; most Minnesota nests started in May of last year were abandoned because of the blood-sucking pests. The current year provides a better comparison because flies were not severe in either state. Yet even when we carry out this “apples to apples” comparison by looking only at 2022 data, Wisconsin platforms look far more productive than their Minnesota counterparts. How can this be?
Let’s be very clear on one point. Lake residents in both Minnesota and Wisconsin are moving heaven and earth to help loons. Indeed, folks in both states who float platforms for loons commonly shift them from a first spot to a second and even a third, if doing so keeps nests safe from mammalian egg predators, eagles, waves, and curious humans. It makes no sense to suppose that Wisconsinites are better or more committed platform monitors than Minnesotans.
How then might we explain this curious cross-state disparity in platform success? Perhaps the difference can be attributed to lake size. Since more of the platforms that we study in Minnesota are found on large lakes, the lower rate of fledged chick production from platforms in Minnesota might simply result from higher wind and boat exposure on large lakes, not any state-to-state difference. Lake size, however, cannot explain better platform outcomes in Wisconsin. As the graph below illustrates, the proportion of hatched chicks that actually survives to fledging age is higher in Wisconsin both on large and small lakes. Furthermore, survival of hatchlings is, in general, a bit higher on large than small lakes. So having more large lakes in a sample should increase fledging success, not decrease it.
The new graph does shed some light on the platform pattern. Chicks seem to fledge better in Wisconsin at least in part because more hatched chicks make it to adult size. That is, part of the reason for greater fledging success at Wisconsin platform nests is high chick survival, not necessarily high nest survival.
Could it be that platforms are somewhat overused in Minnesota? In the past two years, 67 of 141 Minnesota nests (48%) but only 43 of 195 Wisconsin nests (22%) have been placed on platforms. Maybe in their zeal to support the state bird, some Minnesotans have lured loons to nest on lakes or parts of lakes that are unsuitable for rearing chicks. At present, this is only one speculative hypothesis to explain the rather low fledged chick production of Minnesota platforms. But it is certainly worthy of investigation. *
Featured photo by Woody Hagge
*I must quickly note that most platforms in Minnesota seem well-placed. Some clearly provide loons an opportunity to nest in locations that lack nesting habitat but where food is plentiful. Such locations are perfect for platforms and must help the loon population produce more chicks than it would otherwise.
We all love loons. So naturally we should take any step we can to help them. Right? In that light, artificial nesting platforms (ANPs), or loon rafts, would seem to be a no-brainer. Platforms make it easier for loon pairs to produce chicks.
ANPs fit neatly within the framework of loon conservation. Accepted enthusiastically by most loon pairs, they would seem to provide a perfect, low-cost solution to increase loon populations. They are easy to construct; a person with a modicum of carpentry experience can find plans online and build a platform in a day or less. So platforms provide a simple method by which a single loon enthusiast can improve the breeding success of a pair of loons for many years. Across the loon breeding range, platforms have become a panacea for bolstering reproductive success.
But are nesting platforms all that we need them to be? Now that loon populations appear to be in trouble in Wisconsin and perhaps even in Ontario — and now that some of the causes of declines are beginning to come into focus — maybe it is time for us to step back for a moment. Maybe we should ask whether platforms address the actual problems that loon populations face. To state it technically, can platforms mitigate the specific negative factors hurting loon populations and make populations viable in the long term?
We first need to recognize that platforms address a single, very narrow problem faced by loons. Loon pairs must sit on their eggs — in an exposed location — for 28 days. If a mammalian predator wanders by during that month, the nest is lost. Platforms solve this problem beautifully. They increase the rate of hatching by about 70%. But increasing of hatching success is all platforms do. Platforms put more small chicks in the water — a pleasing outcome for folks that deploy them — but they do nothing to help those chicks reach fledging age. They do not feed chicks; they do not protect chicks from predators. They do not boost adult loon survival. They have no effect on the rate of boat strikes or angling casualties or lead poisonings of adults and chicks. In short, if loon populations suffer declines owing to reduced hatching success, then nesting platforms are just what the doctor ordered. If declines are caused by anything else, then platforms would appear ill-suited to the task.
What do we know at this point about the status of loon breeding populations and factors that might threaten them? Precious little, I am afraid, especially if we are speaking of the entire species range. But we have begun to identify specific threats to loon populations in the Upper Midwest.
How well does the use of nesting platforms to boost hatching success of loons map onto the quadruple threat of increased black flies, decreased water clarity, lead poisoning, and spiking mortality of young adults? With respect to black flies, platforms might mitigate the problem somewhat. Platform-nesting loons suffer abandonments just as severely as do loons nesting at natural sites, but the increased hatching success of second nests on platforms offsets the hit to hatching success caused by black fly-induced abandonments of first nests. Platforms, of course, have no impact on the decreased growth rate and increased mortality of loon chicks owing to declining water clarity and the resultant difficulty of feeding chicks. Likewise, platforms cannot affect the incidence of lead poisoning in an area. And platforms cannot possibly save young adult loons from whatever has caused them to die at such an alarming rate in recent years.
On the whole, then, floating nest platforms do not appear to address effectively the threats faced by loon breeding populations (to the extent that Wisconsin represents loon populations generally).
While that quick analysis might seem reasonable, I have ignored one crucial fact about loon nesting habitat and platforms. Platforms often provide loons with an opportunity to breed in lakes or parts of lakes where they otherwise could not because of the absence or poor quality of nesting habitat. In other words, platforms actually create new nesting habitat. If the new nesting habitat that platforms make available contains enough food that parents can fledge the chicks they hatch there, platforms might provide “bonus chicks” that give the loon population a boost. *
Of course, platforms are so enticing to loons that they must be deployed thoughtfully. A platform placed on a very small lake might lure a pair of loons to use it but result in starvation of the chick(s) because of food limitation. Since a pair lured into such a tragic situation might otherwise have nested and reared chicks successfully elsewhere, such misuse of nesting platforms exacts a cost on the breeding success of the population. (Loon conservationists recognize the pitfalls of using nesting platforms thoughtlessly and only deploy them where they are likely to do more harm than good.)
While loon platforms seem effective at boosting loon populations in some respects but appear ineffective or even harmful in other respects, what conclusion can we reach? Lacking hard data, we can only speculate. However, it is probably safe to conclude that judicious use of nesting platforms in lakes or parts of lakes that lack good nesting habitat adds enough “bonus fledglings” to the population to make platforms an effective conservation tool. Indeed, with the list of threats to loon populations growing, we might soon face a situation where we are casting about for new loon habitats with plenty of food but nowhere to nest — so that we can rely upon platforms to place a good many more chicks in the water.
* Population ecologists will recognize a potential flaw in my reasoning. Even if platforms result in a huge increase in fledged chicks in a population, density-dependent mortality during winter or migration (e.g. owing to food shortage) might wipe out all of these extra individuals. In that case, platforms would not be an effective conservation tool. In fact, increased adult mortality from a variety of causes could produce population decline even in the event of huge “bonus” chick production via platforms.