breeding decline

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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.

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Few territories in the Wisconsin Study Area rival Flannery Lake in the futility of its breeding efforts. Despite at least one breeding attempt annually, Flannery has hatched only nine chicks since 1996. If that does not sound too bad, then consider that only two of those nine chicks reached ten weeks of age — the age at which young juveniles can be considered to have fledged. Moreover, one of those two fledglings was severely emaciated as a consequence of its father’s death, the father’s replacement by a new male, and the stepfather’s cruel treatment of it. We are quite doubtful that this unfortunate juvenile made it off the lake and migrated.

We cannot blame Flannery’s poor breeding record on the ineptitude of a few breeding adults. Over the quarter century of fruitless breeding attempts, four different males and four different females have ruled the lake, incubated eggs, and witnessed the loss of the nest or young. Each adult, in turn, has — it would seem — fallen victim to the lake’s curse. The breeding drought of the lake appears even more peculiar when one considers that Flannery was the most consistent and productive lake in the study area from 1991 to 1995. It is as if someone threw a switch in winter 1995, and the lake’s fortunes turned.

A cruel irony of Flannery’s reproductive struggles is that it possesses two clear hallmarks of a successful loon territory. The lake is both large enough — at 141 acres, counting its attached sister lake — and rich enough in nesting habitat — multiple islands — that we might have expected better. Indeed, every regular lake in the study area has outproduced Flannery in chicks, including dozens far smaller and with less suitable nesting areas. How has Flannery been able to do so little with so much?

Does Flannery merely typify the pattern of reproductive decline that I have mentioned so many times in recent blogs? That is, is Flannery simply a victim of the reproductive downturn that has hit all lakes in the area? No, the downturn of Flannery occurred much earlier and is far steeper than the downward slide of other study lakes. Flannery is truly unique.

I cannot solve the puzzle of Flannery’s demise as a chick-producer. I have consulted lake residents to learn why so many nests placed in safe locations have been inexplicably lost, so many healthy chicks have vanished without explanation. Some residents, like me, are getting a bit paranoid about the pattern. One said, years ago, that they thought “teens” might be to blame for disturbing nests and perhaps even taking eggs. But that possibility does not pass muster; surely teens that started hounding the loons or grabbing eggs in 1996 would have grown up and ceased this behavior by now.

Despite my unpleasant experience in tracking Flannery’s breeding history, I hold out hope for them each year. This year, I always think…..THIS year will be the one when they turn it around. In 2021 and from now on, perhaps, Flannery will come to resemble Muskellunge, a lake of similar size to Flannery and less breeding habitat — and one that has produced ten times as many chicks. Owing in part to the diligent egg-turning of the male and female there (see Linda’s photo), Muskellunge should hatch their eggs (again!) within a few days. Maybe Flannery will become the Muskellunge of the 2020s. Quite frankly, I do not see why not.