My world gets turned topsy-turvy each year when the first chick hatches. Each year at this time most pairs are struggling just to hold their territories, find safe nesting sites, lay eggs, and fight off the black flies that chew on them. Today, for example, I visited four established pairs that had built nests and laid eggs, but only one — I am proud to say it is the pair on our home lake, Currie — is still incubating the eggs. The others had abandoned their nests owing to black fly infestation. Four lakes is too few to draw conclusions, but my findings today illustrate the debacle produced by black flies again this year. I am just not quite sure how to reconcile the carnage I saw today on my circuit of lakes with the engaging photo that Linda Grenzer took of the Jersey City male alertly guarding his chick.

I suppose the clearest message sent by the news of a successful hatch is that the world is varied and bright spots remain. Indeed, many loon pairs are beating the black flies and thriving. In fact, a few dozen pairs will follow JCF’s lead and hatch young in the next week or two. Moreover, most pairs that have fallen victim to black flies will lay a second clutch of eggs shortly; there is still ample time to hatch and rear young that can migrate south in November. So do not worry if the loons on your lake are swimming distractedly about right now instead of sitting on eggs. They will likely get back to it soon. In the meantime, take heart — as I am trying to — in the photo above.



What I witnessed on Wind Puddling Lake yesterday is an occurrence we have seen many times now. Instead of the usual two-egg or one-egg clutch, a pair has three or even four eggs. Why the supernumerary egg(s)? There are two likely explanations. First, the female’s cycle of egg production might have been thrown off, causing her to add a third egg, when she would normally have shut down after two. Second, the female laid two eggs, then the pair abandoned them, but they have reused the first nest site and simply added two fresh eggs to the two, old, addled ones from their first nesting attempt.


We know that both 3-egg clutches and reuse of a nest containing abandoned eggs can explain extra eggs in loon nests. In 1997, the Washburn Lake female laid three viable eggs within a single nesting attempt. All three eggs hatched, in this case, producing three small chicks. But the task proved too much for the pair. They lost two of the chicks quickly and settled for raising of a single chick that year. That is the only case we know of where a female deposited three eggs in quick succession into a nest and had them all hatch. All other cases of three or four eggs in a nest have resulted from adding of two new eggs to a nest already containing two old, dead eggs from a first abandoned clutch. This is quite common.

Why would loons behave this way? First, let me point out that safe nest sites are sacred to loons. That is, they search — sometimes for years — to locate a site safe enough that the eggs hatch. Once a male has found a successful nesting site, he is loathe to leave it. So we can understand why a pair might wish to reuse a good site. The question is: why do loons not remove spoiled eggs from a nest before laying fresh eggs there? While it would seem highly inefficient to sit on four large eggs, when you are used to sitting on only two, loons have many times hatched chicks from four-egg nests. Thus, loons are capable of keeping four eggs warm. It may even be that the extra eggs provide a bit of extra warmth buffer, since having warm neighboring eggs helps each egg remain warm itself. So perhaps the answer to why loons do not discard the dead eggs is that leaving them in the nest has no cost and might even bring a slight benefit.

Nevertheless, I do not enjoy seeing a sight such as I saw at Wind Pudding. Supernumerary eggs almost always mean that black flies have been savaging the loons again. While not as severe as 2014, 2017 has been another year of black fly abundance. Many pairs have stuck doggedly to their nests, enduring the hateful pests. But about an equal number have already given up on their first nesting attempt or appear on the brink of it. If that attempt occurred at a favored nest location that produced hatched eggs in the past, we can expect to see more sights like this in the coming weeks.

As we expected from the early ice-out, nesting has begun a bit ahead of schedule. Linda’s photo shows “Clune”, a male hatched on Manson Lake in 1998, on a substantial nest mound in a marshy part of Muskellunge Lake. If all goes well for them, Clune and his mate (“Honey”) will alternate incubation duties for four weeks. Their reward will be 1 or 2 needy hatchlings that they will have to shield from the elements, protect from eagles and other loons, and feed tirelessly for three months. With luck, their efforts will yield two big, fat, sassy chicks, like those pictured here.

But they have a long way to go. May is the month when black flies emerge, bite loons mercilessly on the nest, and generally make them wish they had hands instead of wings. Al from West Horsehead reported today that the flies have driven the pair off of their egg for the time being. Since we know from experience that loons are loathe to abandon a nesting attempt, we hope that they will resume incubation shortly. (Surprisingly, eggs can hatch despite loons spending considerable time off the nest.)

I will return to Wisconsin in a few days myself to race around the study area and find what nests I can. I hope to find those nests by observing loons sitting peacefully on them, rather than thrashing about in the water nearby in a vain effort to rid themselves of their winged tormentors.

If you have been floundering lately, as I have, let’s gain some perspective by considering the plight of the Silver Lake loons. The pair’s struggles began in mid-May, as black flies thwarted their efforts at incubating a first clutch of eggs. According to Pat Schmidt, who watches the pair carefully throughout the breeding season, incubation proceeded normally during the nighttime — cool temperatures kept the relentless pests at bay. But the marked female and male were unable to stay on the eggs during daylight hours, when black flies were active and biting. On again, off again incubation finally gave way to abandonment during the last week of May, but the pair reset themselves quickly, adding two additional eggs to the two they had earlier tried and failed to hatch. Despite the cumbersome task of warming four large eggs simultaneously, the birds produced a chick at the very end of June. Their fortunes seemed to have turned.

The greatest risk faced by a breeding loon pair with a chick is our national bird. Bald eagles nest on tall white pines along lake shores and are a frequent sight over lakes. Indeed, eagles are such a routine part of the scenery on the lakes that loons often deign to wail at them as they pass overhead. Eagle fanciers might try to convince us that these raptors even purposely lull loons into a false sense of security with their constant, mostly innocuous flights nearby so that they can occasionally strike at loons suddenly with deadly purpose. An opportunity for such a surprise attack might occur when an eagle appears just above the tall trees at the lake’s edge as a week-old chick’s parents both happen to be underwater diving for food. Perhaps it was such happenstance that allowed an eagle to carry off the Silver Lake chick on July 2nd. In any event, eagle predation brought the breeding efforts of the pair to an unsuccessful close this year.

The sting felt by lake residents at the loss of the chick had begun to abate by July 18, at which point the territorial female, “Copper” (named for one of her plastic leg bands), found herself in a desperate battle. She was beaten badly, chased across the water, attacked from below as she rested on the lake surface, and finally forced to take refuge on land to escape further damage. By the time the violence had ceased, Copper had to be carried, helpless, to the Northwoods Wildlife Center. She died there a few days later.

As I have made clear in numerous posts, males are the ones that battle dangerously (apparently because of senescence) in most cases. So how do we explain the latest Silver debacle? An oddity concerning contestants might offer a clue in this case. Copper, who had reared chicks on Silver in 2014 and 2015, had battled repeatedly for ownership over the past several years with her bitter rival, “Mint”, the previous Silver female and mother of the chicks in 2010 and 2012. Even after losing the territory to Copper in early 2013, Mint was a frequent intruder into Silver Lake. Hence, both females had raised chicks in multiple years with the male, and both were highly motivated to vie for control of the territory. In addition, banding records indicate that Copper and Mint were of very similar size.

Now to game theory. If an animal encounters a long-lived opponent with which it is very closely matched in fighting ability but happens to get the upper hand at some point, it might then pay for that first animal to press its advantage and even kill the opponent. Why? Because our research has shown us that closely-matched pairs of females, like Copper and Mint, often give each other fits. Two females on Heiress and two others on Oscar-Jenny were so close in fighting ability that they traded off ownership of those territories over many years, each female hindered in her breeding efforts because of the constant interruptions of the other. The result was poor reproductive success for both rivals. Although there is enormous risk involved, it might occasionally pay for females to exhibit the vicious battling we associate with males. Specifically, a lightning strike to finish off your archrival might sometimes be worthwhile to avoid a chronic, destructive feud.


2016-05-20 16.48.46

It is late May again. With nesting underway, loons must confront the first of many hazards that stand between them and successful parenthood. Simulium annulus are blood-sucking black flies that attack common loon specifically. In a good year, they make life miserable for loons, forcing them to increase their diving frequency and decrease preening and resting — simply to avoid spending time on the surface, where they are at the mercy of the flies. In a big fly year, like 2014, black fly infestation can cause 70% of all first nests to be abandoned.

While we can understand how bites from flies would make life miserable for incubating loons, why should loons — like the male above photographed today on Tom Doyle Lake — leave their nests? Like many problems in biology and life, this involves a trade-off. A loon that incubates in spite of relentless attacks from black flies can hatch chicks from the nest. But tenacious incubators also face a high threat of blood-borne parasites from the flies, which might weaken them and shorten their lives. On the other hand, a loon that punts on its incubation duties in the face of the flies will lose that nesting attempt but be able to renest two weeks or so later, when black flies are all but gone. Although this delay lessens the chance of producing chicks for the year, it might make sense to a bird that must take a long-term view — favoring health and condition, rather than risking disease for a slightly greater chance of producing chicks.

As I was writing this last passage, I realized that this is yet one more case where we might expect the age of a breeder to have an impact on incubation behavior, based on senescence theory. An aging loon that stands to have only another year or two on its territory might well have greater fitness (i.e. lifetime chick production) by investing heavily in the current breeding year, rather than preserving its health for a future year that might never come. So we might expect male loons, which senesce mightily, to be tenacious incubators during their waning years. (In contrast, young males should readily abandon a nest, when black flies become thick.)

I will certainly look at the data to see if age has an impact on male incubation behavior; I am excited to do so. But there is a catch. As I have noted in a previous post, dual incubation by both males and females muddies the water. That is, we might expect that an old male would boost his eggs’ chances of hatching with heroic incubation during a heavy black fly season, but such a male is unlikely to be able to compensate fully for a mate that refuses to incubate. So at best we might expect that an old enthusiastic male incubator might decrease likelihood of nest abandonment by an amount great enough to justify his efforts.

I will let you know what I find out.


LMG_4295 one day old chick on back

After 2014’s disastrously low chick production owing to black fly infestation, I was anxious that breeding success would rebound in 2015. My concern defied reason. Loons are long-lived, of course, and a few or even several consecutive years of below-average chick production are not enough to have a lasting negative impact on the population. Still, blinded by the irrational human tendency to infer long-term impacts from short-term patterns, I wished to see our loon pairs come back and raise many chicks in 2015, just as Linda Grenzer’s pair has (see photo).

This year is shaping up to be a very good year indeed. As of this date, 31 of the 120 territories we follow (25.8%) have already hatched chicks. In contrast, only 2 breeding pairs (of 112 pairs; 1.8%) had chicks on this date in 2014. That is an unfair comparison, because the black flies devastated early nests in 2014. However, 2013 was a rather good year for chick production, and in 2013 only 20 of 108 pairs we followed (18.5%) had chicks on this date. Although these data are slightly biased because of yearly differences in nesting schedules — that is, 2013 was a slightly later year than this year — 2015 should be an awfully productive breeding season for loons in northern Wisconsin. As a scientist, I am breathing a huge, sheepish sigh of relief!

LMG_4598 Feeding chick on nest

It was actually yesterday when Linda reported that her much-loved and -studied loon pair had hatched two chicks. May chicks are a very good sign! Even a better sign: 75 of 119 territories we observe are on nests, and only 8-10 pairs abandoned their first breeding attempts owing to black fly infestation. In short, we are off to a good start and hope for a bumper crop of chicks in 2015.

Linda’s stunning photo illustrates the exceptional efforts that loon parents make to care for their chicks. In the photo, the female offers a tiny minnow to one hatchling, while the male looks on, and the second hatchling scampers about the nest. In the coming weeks, the pair will offer steadily larger fish to their young. Both pair members — but especially the male — will guard the chicks closely. The male will yodel at any intruders that fly over or land in the territory. He will be particularly vocal this year, because he has two chicks, not just one. The female too will attend the chicks closely when they are young, but she will start to wander off a bit after they reach four weeks of age, leaving her family to forage apart within the territory and even visiting neighboring lakes.

Why do females seem to sherk their parental responsibilities, forcing their mates to take up the slack? We do not know. We suspect, however, that females desert their families and fly off to nearby lakes to draw attention away from their own lake and chicks. You see, intruders are attracted to adults in the water; the more adult loons they see on the water, the more likely intruders are to land. So females with chicks further two goals by “decoying” intruders away from their own lakes. First, they protect their chicks from intruders, which sometimes attack and even kill them. Second decamping females protect their own breeding position on the lake by reducing the likelihood that intruders will find their chicks and target the lake for takeover attempts the following year.

black fly

Black flies have a terrible beauty. From a distance, they are merely pests, which we must tolerate for a few weeks each year. Up close, they are carefully crafted machines with specialized sensory capabilities and sharp tools sculpted to pierce the skin of mammals and birds and extract the blood they require to nourish their eggs. You have to respect them from the standpoint of evolutionary design.

Yet I spend little time admiring these creatures. Indeed, I dread the two-week period in early May when adult female black flies (Simulium annulus) emerge in vast numbers and descend upon loons. Black flies render each day a trial for loons, which are trying to locate nest sites, mate, build nests and prepare themselves for four weeks of joint incubation. Hounded by flies throughout daylight hours when they are above water, loons drop their normal routine and begin to dive incessantly to minimize blood lost to the flies. Breeding pairs that have completed nests and laid eggs are often forced to abandon efforts to incubate them owing to the relentless insects.

In the past several days, fly populations have spiked, and loon pairs are now suspending their breeding efforts for the moment and simply ditching the flies. We hope that loons’ nesting efforts are not so closely synchronized with fly emergence this year as they were last, when black flies reduced loon breeding success dramatically. If this is a typical year, a small percentage of loon pairs (say, 10-20%) will abandon their eggs on account of the flies, but many more pairs will persevere in spite of the pests. So our hopes for a banner year of chick production are, as yet, intact.

Although their travails pale in comparison to what loons face, even loon researchers are impacted by black flies. Eric, Joel, and Chris are in the final stages of covering the study lakes for the first time. Since they are trying to observe leg bands of loons that are diving constantly to avoid flies, the LP team will confront a steep challenge in the next few weeks. I hope they are up to it!

By any reasonable measure, 2014 has been a dreadful year for loon reproduction. Even if we capture every remaining loon chick that we know of, our total number banded will be almost exactly half of last year’s total. Clearly, the black flies hit the loons’ breeding efforts in the mouth, and they could not recover. Still, it is only one year. As my work has shown me over the past two decades, breeding success is a roller-coaster. In fact, if you combine last year’s bumper crop of chicks with the withered output of this year, the message is that loons are producing enough chicks to sustain the population. So all is not lost.

There have been a few bright spots this year. Though we were alarmed in early June when the Jersey City Flowage male ingested a fishing lure and became hopelessly entangled, the folks at REGI were able to save the bird, he was released near his old territory and recovered — except for possession of his territory! The REGI folks were brought an emaciated chick found by a roadside that they fed back to reasonable health and that we were able to foster successfully to a loon family that has raised it as their own. We recently banded both this fostered chick and its sibling, a true biological chick of the pair. Both chicks have become big healthy, strapping young birds, thanks to their parents’ tireless efforts.

In short, life goes on. I am confident that we will long remember 2014 and not wish to repeat the experience. But perhaps we should best remember 2014 as a year that, while dismal for chick production, was balanced out by strong reproductive years surrounding it and did not pass by without a few cheerful tidings.