Beating the Odds: Ancient Male at Townline Keeps Cranking Out Chicks


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He doesn’t look it, but this male from Townline Lake, just outside of Rhinelander, is at least twenty-seven years old. He is among a dwindling few males from among those we banded in the mid 90s. This bird was banded in 1994, at which point he was certainly at least five years old, which means that he was hatched in 1989 or before. Thus, twenty-seven is a minimum estimate for his age.

The age of “Silver over Red, Orange over Green” (as I call him affectionately) is not his only remarkable attribute. What sets this individual apart from most others is his ability to hold onto his territory year after year while fledging healthy chicks. (Below, he relaxes near his mate and two strapping chicks from 2016.) A successful common loon is not only good at locating safe nest sites and defending and feeding young. A breeder that wishes to

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reproduce successfully must confront intruders that land in the territory without warning throughout the breeding period.

Intrusions are especially frequent during the chick-rearing period. A common scenario plays out as follows. Early in the morning, a male is diving for food, while his two chicks track his progress from the surface. Each time he surfaces, the chicks rush over to him, snatch food from his grasp, and nibble relentlessly at his bill, neck and chest, signaling their unquenchable appetites. On one occasion, he surfaces holding a small yellow perch, only to find five adult loons in flight above his lake. He drops the fish, gives a short barking call, and the chicks dive and head to the nearest shore. The male too dives but surfaces near the middle of the lake, drawing the now-descending intruders to himself. Three quarters of an hour later he has driven off the intruders, thanks in part to a lunge and point yodel that caused his five visitors to scatter and tremolo. Shortly afterwards his mate returns, and both parents forage for the chicks. The family suffers no further disruptions until the evening, when another group of three nonbreeders circle and land, causing yet another brief skirmish.

Considering that a large pool of territorial intruders are constantly sizing up the resident male or female of any successful territory for an eviction attempt, it seems remarkable that residents are able to hold on to their territories for even a single year. Yet Silver over Red, Orange over Green has put together a string of 23 years of straight ownership, the only blemishes a half-year in 1996 and another in 2003, when he was briefly deposed. He has fledged 20 chicks during his breeding career with four different mates. This male is not the only resident with an impressive resume. A female on nearby Langley has fledged 17 chicks on that territory since 1995, while the O’Day female has been on territory since at least 1997 and has produced at least 16 full-grown chicks during her breeding career.

But female loons are survivors. Females enjoy a high rate of survival and no detectable senescence well into their twenties. Males, on the other hand, hit the wall abruptly at age 20; almost half of all territorial males of age 20 will perish before the subsequent year. So when we see a male who defies the odds, like this one, it is worth looking closely to see if he possesses an attribute that sets him apart. As a scientist, I am loathe to draw conclusions based on a sample of one. Colleagues in my field would dismiss any such conclusions out of hand. But today Nelson, one of my Chapman research students this year, reported that Silver over Red, Orange over Green is the tamest bird we have ever measured in the study area. So let me invite ridicule by advancing a very preliminary hypothesis. Perhaps the key to lifetime productivity in a habitat rife with human recreation is picking one’s battles carefully. Maybe by ignoring the inquisitive, well-meaning primates in their watercraft, this male has been able to conserve his metabolic resources for provisioning young and driving off pesky intruders.

Home Alone on O’Day


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Why would a breeding pair of loons — which has made an enormous investment in defending a territory, finding a nest site, incubating their eggs for almost a month, and then rearing their chicks — leave them alone? Such behavior seems reckless, almost dysfunctional. Yet loon pairs commonly “desert” their offspring for periods of hours, while they themselves visit neighboring lakes. During such times, of course, chicks are left to cope with all manner of predators and other dangers without parental assistance.

The leaving of chicks behind by parents does not occur willy-nilly. That is, not ALL chicks are deserted, only those that have reached at least four weeks of age. Some chicks, like those I watched on O’Day Lake this morning, are highly alert to their surroundings, like adults, and capable enough hunters that they are already providing over half of their own food. (Note the expert-looking dive by the chick in the video.) One can imagine that temporarily leaving behind chicks of this age does not carry huge risks. At six weeks of age, chicks can detect and flee from eagles, when necessary. So perhaps the risk of leaving your chicks to fraternize with neighboring adults is not great.

Still, temporary chick-desertion surely carries some risk. If the choices are remaining on your territory with your chicks versus departing to a nearby lake to visit with other adults, the first option is clearly the safer one. The only conclusion to draw from what appears to be rather reckless socializing by pairs with chicks is that they must gain something nontrivial from doing so to compensate for the small risk that their chicks will be lost during their absence.

Their are several possible explanations for parents’ trips to neighboring lakes. One hypothesis maintains that parents encounter and become familiar with neighbors whom they might have to battle later for a territory or with whom they might pair in the future. If so, recognizing and learning about other adults might provide for more effective fighting or breeding. A second idea is that parents leave their chicks in order to forage on lakes other than their own so as to maintain robust food levels for the chicks. Thirdly, temporary desertion of the chicks might constitute part of the weaning process; chicks often beg incessantly when with their parents, and perhaps chicks must be without parents to begin foraging effectively on their own in preparation for adulthood. A fourth explanation is that parents, which are conspicuous to other adults owing to their bright plumage, desert their breeding lakes in order to avoid giving away the fact that they have chicks. (Behaving this way might reduce the likelihood that a young nonbreeder could target the territory for eviction, since we know that intruders use chicks as an indication of a good territory.  ) If this explanation is correct, then parents are essentially trying to “decoy” intruders away from their own lake by visiting a neighboring territory nearby. The hypothesis is plausible, because: 1) intruders are strongly drawn to other adults in the water, and 2) intruders appear to find chicks only after seeing and approaching the chicks’ parents.

One final curious behavior seen in loons and chicks provides partial corroboration for the “decoy hypothesis”. When faced with an intruding loon flying over their lake, adults and their chicks dive and scatter. That is to say, adults and their chicks make every effort to hide from intruders by diving and spreading out in the lake, which complicates discovery. If loon parents are desperate to hide their chicks from intruders, what better way to do so than by flying off to other lakes near their own — and thus using their conspicuousness to draw intruders to those lakes — and leaving their cryptic chicks at home, where they will most likely escape notice from the air.

The decoy hypothesis is complex. Its crux is that loon parents are protecting their own future breeding prospects by taking a slight risk with their current chicks. In time, we will be able to determine if parents that practice short-term chick desertion enjoy longer territorial tenure. If so, this will be a stunning example of effective long-term planning in the animal kingdom!


Misdirected Parental Care: Loons Rear a Goldeneye Duckling


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With Mother’s and Father’s days still fresh in mind, maybe this is an apt occasion to relate a quirky instance of parenting in loons. The topic came up abruptly last week, when Doug Giles, a lake resident in British Columbia, sent these photos. At first, I could not even

_IMG0771 fathom what species of duckling was receiving this unanticipated caregiving. A frantic web search of ducks breeding in the vicinity revealed that this is a young Common Goldeneye. But how could such a duckling escape the watchful eye of its own mother and blunder into the path of a pair of loons?

The curious breeding behavior of goldeneye ducks provides a clue. Goldeneyes lay 7 to 10 eggs in tree cavities, and the female is the sole incubator. (Male goldeneyes leave the picture shortly after incubation begins and play no role in rearing offspring.) Goldeneye ducklings follow their mother away from the nest a few days after hatching. Unlike loons, goldeneye young feed themselves; their mother merely protects them and guides them to feeding areas where they are relatively safe from predators. The task of herding ten or so ducklings about creates logistic hurdles; ducklings commonly fall behind or lose track of their mother and siblings. When goldeneye hens converge in the process of guiding their respective broods, young intermingle, creating creches of dozens of ducklings of varying parentage. Finally, female goldeneyes, especially those with small broods, often abandon them — leaving the ducklings to fend for themselves or coalesce with broods where the female is still present.



In short, rearing of massive goldeneye broods seems haphazard and impersonal when compared with the parental behavior of common loons. If common loons are modern-day human parents in the era of small families, abundant participation awards, and kindergarten SAT prep; goldeneyes are the all-out reproducers of the pioneer days, never quite certain of how many young they have and where they all are! So we should not be surprised to encounter a misplaced or forgotten goldeneye duckling.

But why would loons adopt a young animal that differs markedly from a loon chick? First, it is important to understand that loons — like many animals — are hormonally primed to care for young. That is, young production is the crucial measure of evolutionary fitness, so we should expect all species to be committed to the rearing of young, if parental care is obligatory for survival in that species. Apparently, the drive to provide parental care is sufficiently strong that it can get misdirected at times. Among all ducks that loons might adopt, goldeneye are a good match, as they are diving ducks (not dabblers, like mallards) and subsist mainly on aquatic invertebrates and occasional small fish. Clearly this duckling is developing more of a taste for fish than is usual for its species, as Doug Giles’ first photo shows. The duckling’s willingness to accept food from another individual, moreover, shows impressive flexibility in behavior that we might not have expected.

While we can understand how the adoption of a goldeneye by loons is plausible, it is still a remarkable event. The likeliest outcome of a close brush between a small duckling and a loon pair is an attack; many ducklings are killed by loons each year. Perhaps this loon pair was primed for adoption by having lost their second chick shortly before they encountered the stray duckling.

One factor to which we definitely cannot attribute the successful adoption is relatedness between ducks and loons. Ornithologists have long known that ducks and geese are not closely related to loons. In fact, goldeneyes are cousins of turkeys and chickens, while loons are in the evolutionary lineage that includes herons, cormorants and penguins. The superficial similarity in appearance between loons and ducks results from evolutionary convergence, not common ancestry. In my view, the distant relationship between loons and goldeneyes is yet one more reason to marvel at the odd parent-offspring bond that has formed here — and hope that it leads to a good outcome.


More Carnage at Blue-Southeast


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Mina caught the tail end of the battle. By the time he arrived for his observations, the territorial male on Blue-Southeast was on his heels. No doubt shell-shocked from a beating he had received from an aggressive four-year-old male that had lurked in the neighborhood for two years and was making a play for territory ownership, the territorial male beat a hasty retreat, actually flying off of the lake with another intruder.

The strategic retreat of the territorial male left his mate in dire straits. Without another parent to engage intruders, the female alone had to defend the week-old chick from the aggressive onslaught of the four-year-old male. The situation was hopeless, the suspense only fleeting. The young male quickly discovered the chick and — in the grisliest moment we have observed while studying loons — snatched the chick out of the water and carried it for a time while pursuing the retreating female. When he dropped the lifeless youngster, it was over.

When the shock wears off, we will one burning question about this episode: “Why is Blue-Southeast the site of such frequent territorial controversy?” Can it be coincidence? One must never be hasty to rule out chance, but I think that is not the explanation here. Rather, evictions of the territorial male in 2015 and the same individual again this year resulted from his relatively poor fighting ability. Intruding loons are adept at sniffing out weakness in territorial residents. When a breeding male or female is unable to drive competitors forcefully off of the lake, intruders congregate, leading to further confusion and attempted evictions, in a disheartening positive feedback cycle. The Blue-Southeast male, while a capable parent, has often encountered intruding males that he could not drive off of the territory in years past. It is quite possible that his troubles in 2015 occasioned more territorial challenges in 2016 by the same set of challengers.

I am by nature a rather negative person, always quick to point out the downside of every cheery situation. But I see one bright spot here. If the usurper of the territory and killer of the chick becomes the territorial male, he would appear to be a strong and aggressive individual and one likely to defend the territory with greater success than his predecessor. This 2012-hatched product of nearby Bolger Lake would be a record-setter too, since he would be the youngest male ever documented to seize a territory by force. (Most young males, like very old males, settle on vacant territories rather than fighting their way onto occupied ones.) I wish I could offer more meaningful solace to Blue Lake residents, who will be dismayed at today’s turn of events. The best I can do is to suggest that the future for the Blue-Southeast pair is likely to be brighter than the recent past.









A Challenge with a Possible Upside


Our field work is fundamentally challenging. We observe a large aquatic bird that spends much of its time underwater and surfaces unpredictably. With rare exceptions, individual loons are impossible to distinguish, so we must observe their colored leg bands to tell who is who. Thus, we can only conduct our research by obsessively monitoring leg bands when we can and matching what we see of leg bands with behaviors that the birds carry out. A typical field observation is: “Blue on right leg two-note wailed at 0643 while an eagle flew overhead more than 50 meters away — while the caller’s mate and chick were more than 20m away”, which would elicit a datasheet entry of “643twmc/EF” in the slot on the datasheet reserved for that loon. But sometimes important behaviors occur that we cannot assign to an individual loon. If we are only just approaching a pair when a behavior occurs, or have lost them between dives, we might have to make such an entry into a section of the datasheet entitled “Unknown Pair Member”. Such an entry would indicate that we knew that the caller was one breeder or the other, but could not be certain of identity. Naturally we try to minimize entries into the Unknown Pair Member field, as they reduce our capacity to quantify commitment to parental care and territory defense by the male and female.

To maximize the quality of our recorded observations, we carefully select contrasting color bands for pairs that we capture and mark. The breeders on Swamp Lake, for instance, are: FEMALE -> silver over red – right leg, orange over orange – left leg; MALE -> silver over yellow, mint over white. On Swamp, a quick glimpse of either leg of either pair member suffices to identify it, so we do well at assigning behaviors to the correct pair member.

Territorial evictions mess up our plan of having each breeder banded in a way that differs strikingly from its mate. When a new banded bird usurps a territory, its bands might happen to be quite different from those of its new mate or might not. Back in 2006, when a young male that we had banded as a chick (we term such loons “ABJs” for “adult banded as juvenile”) kicked the resident male off of the Oneida-East territory, the new pair had bands: FEMALE -> Silver over blue, orange over orange; MALE -> orange over orange, green over silver. It instantly became rather difficult to obtain good data on this pair, because they were skittish and because the occasional flash of orange color that we could see on a loon did not allow us to I.D. it unless we were certain of which leg we had seen.

Yesterday, Julia (pictured in her selfie above) reported our worst yet case of eviction leading to headaches in identification. Julia’s observations showed that “white with blue stripe over silver, green over green” had just evicted the resident male on Hilts Lake and paired quickly with the resident female, who is “silver over white with blue stripe, green over green”. Hence, the Hilts pair now consists of a male and female that are identical in the four bands on their legs and differ only in the transposition of the two bands on the right leg. Naturally, behavioral observations of this pair will be taxing for the observer — a real test of our ability to spot subtle differences in band combinations under field conditions. A great many observations of this pair will have to be dumped into the “Unknown Pair Member” box.

Often it is the unwelcome challenges in scientific research that can lead to advances in understanding. Loons do exhibit slight differences in details of the white stippled chin strap and the triangular patches of fine white stripes on the collar. Maybe photos we take of the Hilts male and female will reveal consistent differences in these markings that permit us to distinguish pair members there. I have long mused about the ability of the loons themselves to tell each other apart from a quick glance and without vocal cues. Perhaps the inconvenient turn of events on Hilts will spawn a new, more detailed look at how loons solve that essential but most vexing task — rapid visual discrimination between mates and territorial opponents.

Are Canada Geese Pushing Loons off of Prime Nest Sites?


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The goose population has been increasing in northern Wisconsin. Ten years ago, a Canada Goose was an infrequent sight on one of our study lakes. Geese were confined chiefly to a few large lakes and seen overhead only as they migrated northwards. But no more. Now we encounter adult geese and often pairs with goslings on about half of our study lakes.

Apparently the increased availability of waste grain from agriculture, the proliferation of lawns, and increased temperatures have fueled the explosion in goose numbers, which has the potential to impact loon reproductive success. You see, geese and loons both prefer nesting sites safe from mammalian egg predators like raccoons and foxes. Such sites are often on islands and are limited in number. If a small island offers the only available safe nesting on a lake, goose and loon pairs are both likely gravitate to it.

The problem is not merely that loons must now compete with geese for nesting sites; geese actually get “first dibs”. While both loons and geese incubate their clutches for about four weeks, geese initiate their clutches two weeks or so in advance of loons. (The earlier onset of goose nesting is evident right now in our study area, as many goose pairs are rearing their broods of two to six goslings, while the earliest loon nests will not hatch for another week or ten days.) On occasion geese and loons nest within a few meters of each other on islands — as we observed on Oneida Lake a few years ago. Coexistence between the species is possible. But the presence of a sitting goose appears to discourage loons from nesting nearby, which often forces loon pairs to select sub-optimal sites for incubation.

Consider the plight of the Clear Lake loon pair. The safest, most desirable nest location on Clear Lake is a small shrubby island off of the public boat landing. Loons have shown a strong preference to nest on this island during most years. This year, the geese got their first, and the loons had to settle for a new nesting location on a long peninsula about two kilometers south. They may hatch chicks off of this peninsula, but the site is not offshore, like the shrubby island, so it is clearly vulnerable to mammalian egg predators.

I am optimistic that this spunky loon pair will be able to pull off a hatch. As can be seen from our shaky video, the male (on the right in the video) is still working on improving the surrounding nesting area, and the pair has a well-constructed nest with two eggs (visible to the left of the female, after the camera pans left). Still, this well-constructed nest will not protect them from a scavenging raccoon that ambles by.



Black Fly Anxieties…and a Conundrum


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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.


We Are Back…and a Good Thing Too!



Sleet greeted me as I landed yesterday at Rhinelander Airport. Since I had come from 75 degree southern California, it took me a few moments to adjust. I hurriedly dug through my clothing and threw on four more layers of clothing, gloves and a woolen cap. Our research vehicle, a 2007 Toyota Corolla, was as reluctant as I was to face the elements. The car sputtered to life, and I drove from the storage box to our research cottage on Currie Lake. A panicked search at the cottage produced most of the items I would need for a day of field observations: binocs, data sheets, life preserver, paddle, GPS.

Meanwhile, Royce, my first field assistant of the year, had arrived. After equipping him for a day in the field, and a grabbing three hours of fitful sleep, we were ready to hit the lakes this morning.

On the first day out, novelty and adrenaline keep one going. Royce and I raced from lake to lake, doing “quick-hitters” to locate pairs. In other words, we wrote down any leg bands the loons would show us readily, mapped any nests we found, and threw the canoe back on top of the car to go to the next lake. (Truth be told, we took a quick break at Dunkin Donuts for two vanilla-frosted and a chocolate creme to bolster our flagging spirits at one point.) All told we hit Soo, Flannery, Julia, Buck, Hilts, Hildebrand, Townline, Langley (the 28+ year-old female there is pictured in the photo), Squaw and Gross. Four of these pairs had nests and two others were clearly making plans. Based on this small sample, almost half of our pairs are now nesting. Considering that we have about 110 more lakes to cover, we no doubt have 50 or so nests to find in the next few weeks. Sadly many of these nests will fail quickly — before we can visit the lake — so we will never record them. In order to limit that tragic loss of data, we will continue quick-hitters until we exhaust our lake list.

This is a stressful way to start the research year, but it is also traditional. Some years, in fact, are worse, as I am unable to enlist others’ help to make a first sweep through the study area. Kristin and Linda’s first round of visits in April to locate returning and newly settled breeders spared us the trauma of having to nail everyone’s identity AND find nests. So we will endure, cheered on from time to time by a selfie — and a very occasional stop at D&D.

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The Missing, the New, and the Unexpected


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The first round of censuses in the study area each year is always bittersweet. On the one hand, it is exciting to see the crop of new young adults that have settled and to wonder how well they will defend their new territories. On the other hand, some old familiar loons are missing. This year is typical in that the disappeared veterans are mostly males. Three of 12 males of 20+ years have failed to reclaim their 2015 territory; only 1 of 12 20+ females have not resettled on their territory from the year before. Thus, male senescence lives!

Among the 2016 no-shows are the Jersey City Flowage male, who bounced back from a nasty fishing entanglement in 2014, regained his territory in 2015 and hatched a chick there. Another loss is the Soo Lake male, who was among the most aggressive in our study area. I still tremble when I recall his response when we played a few loon calls in his direction in 2000. He approached my canoe to within 2 feet, sat right next to me in the stern and glowered for the better part of two minutes. A spine-tingling experience for sure!

Yet the news is not all bad. Six young ABJs (“adults banded as juveniles”) have settled in the study area, providing us with valuable data on loons whose age is known precisely. New settlers include two females hatched in Vilas County — a 9 year-old that settled on Manson and a 6 year-old now paired with the male on Harrison Flowage. New male faces belong to an 8 year-old that took over Brandy Lake (near Woodruff) and a 7 year-old that battled and evicted the 22 year-old male from Oscar Jenny. (Thanks to Jeremy, who observed this eviction in progress.)

Perhaps the most intriguing findings from the first round of lake visits by Kristin and Linda are the serendipitous ones. Kristin relocated one of our oldest males — a bird known to be 27 years of age or older. Evicted two years ago from Muskellunge Lake, this loon licked his wounds and got himself back in the game by settling on nearby Swanson Lake, which had fallen into disuse in 2015. We had not seen this bird in two years and were almost ready to give up on him. Linda found a female with even greater resiliency. This old loon produced a dozen chicks over the years as the breeder on Buck Lake from 1998 to 2009. After her eviction from Buck in 2010, she floated, found a breeding position on Hildebrand in 2012 and produced a chick there in 2013. But she was driven off of Hildebrand last year. Her response to this second setback was typical of female loons — she bided her time and claimed that territory again when the opportunity presented itself. As I confront another season of hauling canoes from lake to lake, my back begins to ache in anticipation. I hope the examples of these two dogged old codgers gives me the strength to persevere!


Visit Here, Settle There; the Odd Territory Acquisition of Loons


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LMG_9628 Manson Lake Male Yodeling

Loons do not settle on territories as we think they should. Traditional models in long-lived animals maintain that hopeful young individuals should be systematic in settling on territories. By current theory, a young loon should explore a certain region within proper habitat, find several territories that might be suitable for breeding, and then routinely monitor those potential breeding spots, waiting for a vacancy to occur. During this exploratory period, it is thought, the young loon gains familiarity with this small cohort of territories that will lead to a competitive advantage in territorial battles with other would-be settlers once a territorial slot opens up. The “foothold hypothesis”, as I call this model, is quite pleasing and logical. What’s more, there is evidence that many territorial animals gain territories in this manner. Loons do not.

We got another reminder of the quirky territorial settlement pattern of loons this past week, when Linda and Kristin scoured the study area and ID’d the pairs that had taken possession of the lakes we monitor. Among these settlers were many familiar faces — including a male on Townline Lake that has been in possession of the territory since 1994 and a female on West Horsehead who has bred there with a series of different males since 1995. One of the surprises was a 9 year-old female hatched on Rock Lake in Vilas County who settled on Manson, replacing a female that had bred on Manson for a dozen years. Owing to Linda’s careful observations, we know this Rock Lake female as a frequent intruder during 2014 and 2015. But she did not intrude into Manson Lake, where she eventually settled; instead she intruded repeated onto nearby Muskellunge Lake! Thus, our expectation that the Rock female was laying the groundwork for settlement on Muskellunge was not fulfilled.

There are several possible reasons why loons often do not settle on lakes that they seem to prefer. One of the most obvious is that settlement is not merely a matter of finding a desirable territory.  A loon bent on settling must also contend with the current resident on a territory where it hopes to settle. So a young nonbreeder that visits Territories A, B, and C might prefer Territory A but be prevented from settling there by a healthy and aggressive territorial resident of the same sex. In that case, the nonbreeder might end up settling on Territory B or Territory C. The Rock female is fortunate; Manson Lake, where she has settled, is one of the most productive territories in the study area. So even if she could not take possession of the territory she seemed to prefer, her future breeding prospects are bright.

You can read more about our testing of the “foothold model” for territory settlement in this blog post, which is based on a paper published in Animal Behavior. E-mail me if you would like a pdf of the paper.

The crisp photo above is by Linda Grenzer. It shows the Rock female performing a wing flap on Manson, her new breeding lake, while her mate, an 18 year-old male, yodels in the foreground.


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