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In many recent posts, I have emphasized a certain theme: male loons begin to die off at a rapid rate after age twenty, while females linger on. Part of the reason for this contrast is the nature of territorial contests in each sex. Territorial males fight hard in attempting to hold their breeding position on a lake and commonly die in territorial battles. With rare exceptions, territorial females survive eviction from a territory, move to an unoccupied lake nearby, and resettle on a new territory when opportunity permits.

While the escalation of male territorial battles is interesting in itself, it also impacts the composition of the breeding population. Specifically, adult male loons’ propensity to die frequently in battle skews the sex ratio towards females in the breeding population.

These excess females are “floaters” — adults capable of breeding but prevented from so doing by the lack of a mate and/or a territory. Floaters are the loons that one sees living alone on small lakes, drifting about aimlessly on large lakes, and intruding into territories from time to time to confront breeders. A large proportion of the loons that gather in flotillas of five adults or more during July and August are floaters. Floaters can be thought of as “hopeful breeders”; that is, they are always ready to settle and breed with a mate and territory, if they can find one. The excess of female floaters means that there are always far more of them looking to settle and breed than there are male floaters able to pair with them. In effect, males are snapped up by females as soon as they become available for breeding.

In May of this year, we re-encountered one of our veteran breeders, “Silver over Blue, Green over Orange” (or “S/B,G/O”), whose breeding history illustrates the striking contrast between males and females brought about by male-biased mortality. S/B,G/O was first captured and marked as an adult in 1997 on Dorothy Lake, where she raised two chicks with her mate. Her mate was evicted in 2001 and died either during eviction or shortly afterwards. But she lingered on. When an opening became available in 2002, she settled and nested with a different male on Hasbrook Lake, just a few miles to the northwest. Having failed to raise chicks on Hasbrook, S/B,G/O (now at least 14 years old) evicted the female breeder on Hodstradt in 2004, paired with a third male, a six year-old, and reared four chicks there during the next three years. She followed this young male to Horsehead Lake in 2008, when he was driven off of Hodstradt, and the pair fledged 3 more chicks over the next four years on their new lake. When the male was evicted yet again in 2013, S/B,G/O traded experience for youth and found a new six year-old male as a breeding partner. We breathed a sigh of relief when she broke up with this youngster after a year together, as he was unfortunately her son from Hodstradt! Then 23+ years old, S/B,G/O again became a floater, forced to return to the breeding grounds in 2014 and 2015 with no clear prospects for breeding.

I have become attached to the birds in the study area, so I was delighted to find S/B,G/O back at Hodstradt in May of this year with her fifth recorded mate. At 26+ years of age, she is perhaps fortunate to be paired again. Her mate this time: a four year-old hatched on Clear Lake. We observed no breeding attempt by this new pair – only a small percentage of four- year-old males that settle on territories actually nest – but it is likely they will nest in 2017.

As a human, I like to think of S/B,G/O’s life as a lesson in resilience – the dogged refusal of an animal to forsake breeding despite repeated setbacks and advancing age. But, as a behavioral ecologist, I think of this female more as a striking example of how animals adapt to maximize their breeding capacity regardless of the breeding environment they face. By the way, S/B,G/O is not the only female in our study area who has continued to breed despite frequent changes of partner. S/R,O/O, another 26+ year-old from Swamp Lake that we recaptured a few nights ago (see photo with Eric), has gone through at least 5 younger mates during her 20 years of breeding there. Clearly the pairing of tough, old females with much younger males is – as my daughter says – a thing.

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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.

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!

 

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.

Several months have passed since Gabby Jukkala’s and my article was accepted for publication in the Journal of Avian Biology. We have been anxiously tapping our feet while the wheels turn and our article comes out in the journal. This has just happened. You may now view our article here.  Gabby and I are thrilled that: 1) our article has been selected as “Editor’s Choice” for this issue of the journal, 2) Linda Grenzer’s nice photo of the female on her lake with a chick from 2015 is the cover photo for the issue (and a second is featured in the blog spot), and 3) the journal has included extra information about us and our article on their website here.

I have already described the findings we report in the article, so I will not rehash those here, but do take a look at the article, which the journal is making available free of charge, since it is “Editor’s Choice”. It is a very small honor, in fact. Still, these days I am often on the Newport Pier, as that is a good local birding spot and I must prepare for the Ornithology class I am teaching this fall. Whenever a member of my study species wanders nearby, as it forages for mackerel or smelt, I find myself smiling a bit more strongly than before.

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“Wow”, Lainey said, “that band number is right next to the female we caught last night on Sherry”. She was right; the adult male from Skunk, which we had just netted and whose band number I was reading aloud to Lainey for data entry during banding, had a number imprinted on his aluminum USGS band that followed immediately after that of the Sherry female from the previous night. The reason for consecutive bands is that the Sherry female is the mother of the Skunk male and was caught and banded with him a decade ago (less two days) on Sherry Lake. I remember July 31st, 2005 on Sherry vividly, because I was equipped with a video recorder on top of a helmet with which we recorded the capture process for research presentations. But the recapture of mother and son on back to back nights ten years after we had first marked them has also caused me to reflect upon several key features of loon biology that have become familiar to me through my work.

First, loons live a long time. In this twenty-third year of my work, I still encounter birds in the study area that were on territory, as adults, when I first started covering them. Females, in particular, are survivors. While males have rather high mortality –partly owing to their proclivity for battling dangerously — females linger. When their mate dies, females find another; when a female is evicted unceremoniously from her territory, she stoically moves to a new lake nearby and awaits a chance to re-insert herself back into the breeding population. So it goes with the Sherry female whose worn-out band from 2005 is pictured on the bottom in the photo. She was “widowed” suddenly in 2009 (a possible eagle kill) but hung onto her territory and was joined by a new male in short order, who has been her mate since.

Second, young males do not disperse far from their natal lakes to breed. The Skunk male, from whom we removed the top band in the photo last night, moved about 15 miles from his natal haunt, Sherry. That dispersal is, actually, a bit longer than average for males, many of whom settle to breed on a lake adjacent to where they hatched years earlier. Short-distance male dispersal is essential to my work; without it, I would not have a large marked cohort of 2 to 5 year-olds of known age and natal origin in the study area at all times whose territory settlement strategies could be investigated. (At last count, we had seen 295 adult loons in the study area that were marked originally as chicks.)

Third, loons vary tremendously in their behavior towards humans. My assistants and I dread the Sherry female, because she is the most skittish individual we know. She cannot be approached easily within 100 meters on the water; she tremolos (i.e. alarm calls) incessantly when a chick is present and a canoe appears on the water. In fact, my assistants tell me that she begins to tremolo in anticipation of a canoe being placed on the water and that they have begun a strategy of hiding behind bushes and trees along the shoreline in order to make observations of her when she is with the chick. (Fortunately, Sherry Lake is tiny, so this observation strategy is workable.) I joked that we should wear camouflaged clothing when visiting Sherry; my assistants did not find this funny. Oddly, the Sherry female’s mate is among the tamest loons we study and never tremolos at us when we collect data there.

The great variety in loon tameness is a topic of great interest to us, as I have mentioned. It amazes me that an adult such as the Sherry female could react so strongly (and, it would seem, maladaptively) to humans, which she encounters constantly. Doesn’t she waste energy with her fruitless calls? Shouldn’t skittish birds like her leave fewer offspring and live shorter lives than other adults who tolerate humans without constant complaint? If so, she is not a good example of the pattern, as she has behaved this way for the ten years we have known her while cranking out chicks. Indeed, the Sherry female and the Oneida-East male, another vociferous but fecund individual with whom my staff has to cope, make me wonder if I have got it backwards. Maybe loud-mouthed loons warn humans away, lessening the likelihood of injury to themselves and their brood, and are rewarded with high evolutionary fitness.

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Two days ago, Mark Naniot of Wild Instincts got a report that a loon on Two Sisters Lake had been hooked by a fisherman in the leg and was trailing 50 feet of monofilament line and a bobber. Mark learned also that a well-intentioned kayaker had approached the loon and cut much of the line, including the bobber, but leaving the hook and several yards of fishing line trailing. Having captured and unhooked a loon several weeks before on the same lake, we were disappointed to hear of another angling incident. Could the same bird have become entangled again?

Seth happened to be collecting data on Two Sisters Lake yesterday. He found the impacted loon, which was not the Two Sisters-West male that we had rescued in June but the female from Two Sisters-East. (The lake has east and west halves, each with a successful loon pair.) Seth reported that the female was using her right leg sparingly, trailing fishing line, and had tried but failed to take off and fly on several occasions. She was not with her mate and two young chicks. Clearly the bird was in trouble.

After digesting Mark and Seth’s reports, I turned my attention to the prospect of catching the impacted loon. I viewed the challenge with mixed feelings. On the one hand, this female, hatched on Crab Lake in Vilas County in 2004, was well-known to us as a rather tame individual, making capture more feasible. On the other hand, we had captured her four nights earlier, which raised the possibility that she would recall that event and be more difficult to approach a second time. The most crucial card we held was that the female had chicks to protect.

Several major research programs that focus on common loons in the northern U.S. and Canada rely, more than any other factor, on the ability to approach adult loons closely at night and net them when they have chicks. If researchers could not approach adults closely during this reproductive window, we would not be able to mark them and study their behavior, health or survival. We would therefore be unable to generate models to determine whether loon populations are increasing or decreasing. In short, loon research would grind to a halt without the presence of chicks to freeze adults on the surface and permit us to catch and mark them.

Last night’s adventure served as a vivid reminder of the value of chicks to adult capture. We began searching for the hooked female shortly after nine p.m. and located her quickly along the southwest corner of the lake’s eastern half. Her behavior was odd; she seemed to restrict her movements to one small portion of the lake and was not anywhere near her mate or two large chicks. She held her hooked leg out of the water when resting on the surface. Before full darkness, we spotlighted and approached her to attempt capture, but she repeatedly dove before we could get within a net’s reach. Although frustrating, this cheered us a bit, because it showed that she was still relatively healthy despite the hook. At the same time, we were vexed to see that a loon that was in dire need of human assistance and which we had scooped out of the water with ease four nights before was resisting capture. We made several more passes by the female, until it became clear that the distance at which she dove was increasing rather than decreasing. We had a loon in need of help, a huge staff from Wild Instincts on shore waiting to assist it, and no obvious means of catching the bird. The critical ingredient missing was her chicks, which were nowhere nearby and which, we felt, might have held her on the surface and permitted us to net her.

We shut down the motor and listened. As luck would have it, an adult loon tremoloed far to the northwest, near the small bay where the Two Sisters-East pair had nested. Eric drove us up to the northwest corner, where, after 20 minutes of searching, we located the male and two chicks. Freshly banded from four nights before, the male and two strapping youngsters were nonetheless easy to net and pull into the boat. We set out southwards, where we had left the recalcitrant female, and released all three birds there. After several minutes of silence, the just-released male finally wailed and an answering tremolo came from 400 yards southeast. Again, we were in a bind, because the female had clearly swum a good distance away, where she would not soon encounter the chicks that we had released in hopes of capturing her. So again we netted a chick — leaving one near the male — and motored southeast to where we had heard the female. Having glimpsed the female for an instant before she dove, we gently held the chick in the boat until it vocalized. The injured female was transformed: she immediately sat up in the water, alert, and wailed to call her chick to her. We released the chick, the two reunited, and the female remained alert and protective next to her chick as we slowly approached and netted her.

After all of our efforts, it was rewarding to learn that, while the hook had punched cleanly through the female’s leg a few centimeters above her colored leg bands (see photo, courtesy of Wild Instincts), the prognosis (according to Mark) was excellent for recovery.

Looking back, we spent three hours capturing a family of loons that we had just caught and banded four days earlier. The rescue was a major production, requiring us not merely to locate and capture her but to find and capture her family in a remote location on the lake and transport them to her vicinity in order to restore her parental instincts and permit us to approach and net the impacted loon. This effort threw a wrench in our capture schedule, necessitating that we rush to three more lakes to capture loons there and cancel plans to attempt capture at two more lakes. Still, our team effort with Wild Instincts left us glowing; we had rescued a loon in peril and given her a chance to return to her life as a plucky protector of two young offspring.

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The Loon Project counts on efficient exchange of information with lake residents and loon enthusiasts as a means to acquire good scientific data. We cover enough lakes — about 120 this year — so that we make visits to them only once every 5 to 7 days. This permits us to track the identity of the breeding pair and record their breeding activity. Over time, we accumulate important data on territorial fidelity, eviction of breeders, and their relocation to other study lakes. But weekly hourlong visits leave lots of holes in our knowledge. So it is helpful that almost all of our lakes are occupied by humans who take an interest in “their loons” and contact us or the Wisconsin Department of Natural Resources when something is amiss.

Yesterday, a resident on Flannery Lake called with distressing news. The male on the lake, a 14 year-old reared on Washburn Lake, was dead and being fed upon by a mink. We were particularly saddened to hear such a report from Flannery, because the breeding pair had attempted to rear young every year there since we began to follow them in 1993, but had not fledged a chick successfully since 2006. That unlucky string seemed about to be broken when, earlier this month, the pair hatched two vigorous chicks. We were delighted, though perhaps less so than lake residents, who had watched their loon pair build nests, lay eggs, and incubate them diligently year after year only to lose them — or their small chicks — for reasons unknown.

This morning Seth visited the lake to see whether the female and chicks were still alive and whether another male had taken the deceased male’s place. He snapped the photo above, showing that the female, who is at least a quarter of a century old, is alive and well, as are both chicks. However, he also reported that a possible incipient pair was present on the lake. This makes sense. As I have noted in recent posts, male loons use their yodels to keep hopeful settlers at bay. With no male present to yodel, intruders flying overhead readily land in the lake. Since the female cannot safely leave the two-week-old chicks alone, she cannot easily engage intruders and drive them off. In short, Flannery is prone to intrusion and settlement.

Despite the difficulty of her situation, Seth reports that the Flannery female continued to show territorial behavior towards intruders this morning. It remains to be seen whether she can find refuge on the lake such that she can both avoid any new pair that settles and forage to sustain herself and her young chicks. It is a tall order. Indeed, we have only once observed a female whose mate died or was evicted raise a young chick on her own. In 2012, the male on Squash Lake died of lead poisoning owing to an ingested sinker, leaving his mate and a chick only a few days old. The Squash female that summer miraculously succeeded both in rearing the chick to fledging and in pairing with a new male — a lesson to us all that child-rearing need not prevent an active social life. “Miracle Chick”, as we came to call the survivor on Squash, became our most revered juvenile that year. (Miracle Chick is pictured below with Kristin and Gabby.) Lauren's capture video and stills 082

So there is reason for hope for the young Flannery chicks. If she is vigilant and fortunate, a female can raise a chick, perhaps even two, without help from a male. Considering the long odds of such an achievement, we should certainly resist optimism at this point. We will keep an eye on this fractured family, and I will let you know how things turn out.

LMG_3382 JCF Male

We have almost completed the first round of visits to study lakes. Our ever-expanding list of lakes makes this no mean task, as our list has grown from 95 territories in 2008 to 123 this year. Kudos to the field staff of Joel, Eric, Chris, and Linda (whose photo appears above), who have worked hard to visit lakes and ID loons from leg bands — and also Al on West Horsehead and Pat on Silver Lake, who have e-mailed with data from their lakes.

Of 162 banded loons on territories as of late 2014, 141 (or 87%) have reclaimed those territories this spring. Among 21 missing territory holders from 2014, 4 have been resighted in 2015, but were apparently evicted from their territories early this year. Thus, the minimum survival rate from 2014 to 2015 for territory holders is about 90%. This figure agrees closely with survival rates calculated from Wisconsin and elsewhere within the breeding range.

Sky-high return and survival rates for our population highlight a simple pattern in the life history of common loons. In ecological terms, loons are “K-selected”. That is, they are long-lived, take several years to reach sexual maturity, produce few offspring during their lives, and invest heavily in parental care for the few offspring they do produce. Loons are not explosive reproducers that “shot-gun” many offspring out into an uncaring environment in hopes that a few survive. Rather, they work hard to maintain ownership of their breeding territory, eke out one or two chicks a year (in a good year!), and defend their chicks vigorously against all comers!