Too Many Loons in the Water

on June 3, 2022June 3, 2022

One of the pleasing sights of spring in the Northwoods is that of a territorial pair of loons, foraging side by side. No doubt the myth of lifetime fidelity of loons to their mates arises, at least in part, from the tight association of female and male loons at this time. Their apparent devotion to each other, their compulsion to remain together at all times, the touching plaintive wails that keep them in contact when they chance to become separated for a brief period all recall young human couples with limitless possibilities before them.

During the past three weeks in Minnesota and Wisconsin, I have seen many loon pairs foraging, resting, and preening together. It is truly heart-warming — to a degree. You see, once the territory resettlement period — the first three weeks after ice-out, roughly — has come to a close, loon pairs should be nesting, which means that humans watching out for “their loon pair” should see only one pair member or the other on the water.

Egg-laying marks the start of the nerve-wracking 28-day period of incubation where innumerable things could go wrong. A raccoon could wander by; an eagle could flush the incubating bird and feast on the eggs; a sudden downpour could turn a nest that seemed safely above water level into egg soup, cooling the eggs and killing the embryos. But one single cause of incubation failure has emerged as the single greatest threat to loon breeding success in Wisconsin and Minnesota in the past decade. The agent, a single species of black fly with a peculiar taste for loon blood, has recently surpassed even egg predation by raccoons and their ilk as a cause of nesting failure. When hundreds of black flies surround incubating loons and bite them mercilessly on the head and nape, the agony can become too awful to bear, causing the pair to abandon the nest. In recent years, black fly survival and persistence dictate how productive an entire loon population will be. It is that simple.

Yesterday, five of us — four members of the loon research team and a reporter for Minnesota Public Radio — ventured out onto the Whitefish Chain to mop up the few territorial pairs that we had not yet been able to visit this year. The trip was memorable for more than loons. An unexpectedly stiff west wind turned Middle Whitefish into a seething Lake Superior, forcing us to beach our motorboat prematurely at Boyd Lodge. (It took four Blizzards at DQ in Crosslake to help us move on after that hair-raising experience!)

Despite sketchy conditions, we visited nine new territorial pairs. We were thrilled when Kate spotted an incubating loon in a protected cove of Pig Lake. But that was the only territorial pair we scouted that was sitting on eggs. All others behaved as if the ice had just come off: they preened, rested, and foraged side by side. What would have been a cheerful sight in mid-May causes consternation now. Sixty to seventy percent of all pairs should be incubating eggs at this point in the season. Sadly, the featured image from Sibley-South depicts the situation in many of these lakes at present: two perfect golden-brown eggs — and loons nowhere nearby.

What Do We Know about the Minnesota Loon Population?

on November 24, 2021November 24, 2021

I have said a number of times that we do not know how the Minnesota loon population is doing. That blanket statement is misleading. In fact, two well-organized efforts to gather data on Minnesota loons — both run by the DNR and staffed by armies of citizen scientists — have been under way for decades. These massive efforts have given us glimmers of information about the status of loons in the state that I will summarize here.

The Minnesota Loon Monitoring Program

Begun in 1994, the Minnesota Loon Monitoring Program relies upon volunteers to count loons within six regions in the state and produces a summary report every five years. A second project, the Volunteer LoonWatcher Survey, also run by the DNR, began in 1979. Since the MLMP aligns closely with one important goal of our Minnesota work — assessing the status of the Minnesota loon population — I will limit my comments to that survey.

What Do the MLMP Data Show?

Of course, using volunteers — some without boats and binoculars — to measure loon numbers increases uncertainty in measurement. But despite inevitable fluctuations in measurements from individual regions and years, the MLMP survey seems to be an effective tool for estimating loon populations. So it is reasonable to look at MLMP data and expect to see meaningful patterns.

One of the first patterns you notice in the MLMP survey data is the noise within it. The true density of loons on lakes within each region of Minnesota should not vary much from one year to the next, because loons are long-lived and reproduce at a low rate. Yet the MLMP data show huge fluctuations in loon density from year to year, especially in Itasca, Otter Tail, and Becker Counties. That substantial scatter in the data is important, because it makes interpretation difficult.

Second, despite the noise, it is clear that the density of loons varies greatly between regions. The DNR’s analysis shows only one loon per 100 acres of lake in Kandiyohi County (southwestern part of the state) but three or more loons per 100 acres in Itasca County (northern part). The four other surveyed regions — Becker, Otter Tail, Aitken/Crow Wing, and Cook/Lake — have loon densities that fall between these two extremes. Differences in density across the state are significant, because they help us identify regions of particular importance to a species. With apologies to loon lovers in southern Minnesota, if loons are three times as dense in Itasca County as in Kandiyohi, then Itasca is a much higher conservation priority. (This sort of “triage” perspective is the bread and butter of conservation biology.)

Third, population trends — the aspects of the survey in which we are most interested — are dimly visible within the data, despite year-to-year scatter. According to the DNR analysis, two regions — Cook/Lake and Itasca — have seen small declines in loon density since 1994; one — Otter Tail — has seen a small increase; and the other three regions have experienced no significant change. These conclusions highlight one difficulty we face in assessing the MLMP results. If there are two bits of bad news and one bit of good, what do we conclude about Minnesota’s loon population as a whole?

According to the DNR summary, “MLMP results suggest that Minnesota’s loon population remains stable with an average of 2 loons per 100 acres of lake across all six Index Areas.” It would be pleasing to conclude, as this statement does, that: 1) there is one statewide population pattern and 2) that this overarching pattern could be encapsulated so simply. But the DNR’s summary seems to gloss over some worrisome trends in the data.

What Do the Data Show for the Past Ten Years?

In light of the brevity of the DNR’s summary, it seems worthwhile to take a deeper dive into the MLMP. One oddity of the 2020 DNR report is that it uses 1994 to anchor the trend line. Why 1994? Simply because this was the inaugural year of data collection. But we are most interested in the trend over the past decade, because that gives us a better sense of what is happening now. Over the past ten years, Crow Wing/Aitken and Itasca regions both appear to have suffered sharp declines in loon density; Cook/Lake has declined slightly; and Becker and Otter Tail regions have been more or less stable. Only Kandiyohi County provides good news, as it appears to have greatly increased in loon density in the past decade. But since loon density in Kandiyohi remains far below that in Crow Wing/Aitken and Itasca, the good news from Kandiyohi does not even begin to offset the disappointing findings from Crow Wing/Aitken and Itasca.

What is the Real Take-Home about Minnesota Loons?

We cannot reach any firm conclusion about the status of Minnesota loons based on the Minnesota Loon Monitoring Report. There is simply too much scatter in the data for that. However, careful inspection of recent findings reveals worrisome downward trends in two vital loon population hubs. I take these troubling signs seriously. With support from the National Loon Center in Crosslake, I am accelerating my effort (begun in 2021) to establish a large marked study population in one of these two hubs — Crow Wing County. In the next few years, we will produce estimates of adult survival, reproductive success, and other demographic parameters to construct a new population model for the region. Our fine-grained analysis will indicate whether the downward trend suggested by the MLMP data is real and sustained or whether those of us who wish to conserve loons in Minnesota can breathe a great, collective sigh of relief.

Meanwhile in Minnesota…

on May 7, 2021May 7, 2021

As I mentioned a few posts ago, the Loon Project is expanding into Minnesota, the state that contains more breeding loons than any other. Of course, our plan to establish a second study area 200 miles west of the current one in Wisconsin is ambitious. So I have enlisted the help of five LP veterans to help us cover our sprawling study area. These sturdy souls include Gabby and Linda, who are keeping track of our Wisconsin birds until the bulk of the team members arrive in a week, and Kristin, who, joined by new team member Katy, is taking our first look at the Minnesota study population. All of these folks have really stepped up for the Project.

Early-season work is both arduous and exciting. Arduous because we have so many loon pairs to visit. Arduous because these now hundreds of pairs must be visited one at a time and each pair member observed until we are confident we know its identity. But also exciting because we have not seen these birds since the previous summer, if at all. During the fall, winter, and spring periods, many of our loons have died or been evicted by younger rivals. And many of these young upstarts are birds we banded as chicks five to ten years ago on adjacent lakes.

Minnesota is a whole different ballgame. When we decided to take on the task of starting a new study population on the lakes in and around Crosslake, we knew that we were making a pledge to cover brand new lakes whose loons were abundant but little known. We also understood that, unlike our breeding pairs in Wisconsin, most of the Minnesota loons defended territories on the massive Whitefish Chain, where our protocol of dropping solo canoes in at boat landings and paddling to the birds was unworkable. In short, we were pledging to take on a new study population that required a completely different mode of research.

I couldn’t wait to get started. Though tethered to my instructional responsibilities in California, I gazed at these unknown Minnesota lakes on Google Earth and felt my excitement build. I collected what information I could about the lakes and loons from folks in the area. I studied maps of loon activity and banding logs provided by Kevin Kenow of USGS, who captured and marked a few dozen birds on the Chain five to six years ago and generously shared his knowledge and data. And I scratched my head.

Since I was out of commission, I needed to find someone with great knowledge of loons and a willingness to confront the daunting challenge of making our first visit to the Chain. I told Kristin that I needed her to: 1) visit an unknown study area, 2) census dozens of unknown pairs, most of which would be unmarked, 3) travel by large motorboat on an unfamiliar lake with tricky wave and wind conditions, 4) work out all of the logistics of this work with a group of unfamiliar (but enthusiastic) Minnesotans, and 5) get permission from her advisor to suspend her Ph.D. preparation and take on the project at all. I am not sure how I managed to ask her with a straight face. Predictably, though, Kristin’s response was: “Oh – that would be a blast!”. And so Kristin has begun this crucial reconnaissance. Joined

Kristin and Katy study a map of the Chain before setting out to find loons.

One of the ten nests found by Kristin and Katy on the Whitefish Chain.

by Katy, a new LP team member who is fluent in the local dialect and has turned out to be a quick study, Kristin has now covered all but a few nooks and crannies of the Chain. As of this writing, K and K have found 45 breeding pairs on the Chain and ten active nests, like the one shown above. Most of the pairs are unmarked, but they report 14 of Kevin’s banded adults are still on territory. (These marked individuals will be most valuable, as they will permit us to make preliminary estimates of territory eviction and survival for the new study population.) K and K will wrap up their coverage of the big water today, they say, and spend the next few days visiting small lakes adjacent to Whitefish. These small

lake visits will no doubt bring a tear to Kristin’s eye, as they will recall the work she used to do back in the Wisconsin study area.

By starting before sunrise, Kristin and Katy made the most of windless conditions.

Kristin and Katy’s effort to establish a foundation for our Minnesota work epitomizes the work of the Loon Project. We pride ourselves in carrying out research that is uncomfortable and physically-demanding, yet also exacting and painstaking. We tackle research questions that most others deem inaccessible. The work just seems too difficult, our study animals too recalcitrant. How can one accumulate sufficient data to test hypotheses about animal behavior and ecology under these conditions?