2016-08-01 02.16.10

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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Loon capture is a blur. We set out from our house at 8:45 pm, launch our small motorboat on the first lake, wait for nearly complete darkness, and catch any loon chicks and parents that we can net easily. By the time we have repeated the process four more times, we are rubbing our eyes, our weariness justified somehow by the presence of the sun lurking just below the horizon.

As an essentially negative person, what I often recall after a night of capture and banding are the physical demands of the process and my complete exhaustion. But there are dimensions of the work that are exciting and rewarding. Each loon is unique, and one never knows whether an individual will permit itself to be approached closely and netted or will be wary and elude us. So we experience many disappointments, but they are tempered by the occasional thrill of capturing an individual that, at first glance, appeared too skittish to catch.

The fruits of loon capture are obvious. By marking individuals and resighting them year after year, we learn about survival rates of adults and juveniles, territory fidelity, natal dispersal, and habitat preference. We glean a good deal of important information from these data. For example, survival rates of young and adults allow us to learn whether the  local population is increasing, decreasing, or remaining stable. And tracking of young loons from egg to first territory has revealed that loons develop strong preferences for breeding lakes that closely resemble their natal lake. Finally, capture is essential as a means to disentangle loons that have been run afoul of angler’s lines or lures.

This year’s capture exposed another distinctive pattern in loon ecology: the presence of ecological traps. An ecological trap is a breeding habitat that appears at first glance to be a good one but ends up being poor for reproduction. For example, a field might experience a burst of insect activity during early spring, enticing songbirds to settle there for breeding, but a crash in insect levels after eggs hatch might occur that suppresses the number of young birds produced. Two nights ago, we captured two chicks from two different lakes back to back. The first territory was a shallow 11-hectare portion of Wind Pudding Lake (my favorite lake name). The chick captured there was a five-week-old that weighed a scant 0.92 kg — less than half what we would expect from a chick of that age. Our daytime observations show that the chick’s parents are no slouches; they respond to its constant begging by making frequent dives and retrieving what food they can to feed it. Moreover, the chick itself dives often to forage. But this shallow lake, covered almost entirely by lily pads (which impair loon foraging), offers scant sustenance. I am afraid that the emaciated Wind Pudding chick will ultimately starve to death, as did the chick on nearby Liege Lake, another shallow lake choked by vegetation. Loon parents on small, acidic lakes struggle to rear even a single chick, whereas those on large lakes of neutral pH often raise two. This stark contrast was highlighted for us, as the lake we visited following Wind Pudding was 1373-hectare Lake Tomahawk. To be sure, loon parents on Tomahawk must steer their chicks through countless jet skis, water-skiers, anglers, and speed boats at all times of day. But vigilant parents are rewarded with abundant food for themselves and their chicks. The Tomahawk-Sunflower Bay chick held by Mina in the photo weighed 3.02 kg, yet it was only a few days older than the chick on Wind Pudding. Clearly the strapping youngster in the photo is heading for a healthy future and likely fledging.

Why on Earth would loons settle to breed on lakes that often provide too little food for their chicks? The answer might relate to the disconnect between nesting and foraging requirements. Alas, large lakes that contain many fish for loons often lack the islands, emergent marshy bays, and bogs that allow loons to avoid egg predators like raccoons. So loons looking to breed seem to be lured onto small, marshy lakes that yield successful hatches but doom their offspring to starvation.

LMG_7851 Walter n Sammy

The season began inauspiciously at Crystal Lake in Lincoln County, which is along the southwestern fringe of our study area. Though it is a pleasant, rather clear lake, Crystal offers no nesting habitat for loons. Loons love most of all to place their nests on islands but also make use of boggy or marshy areas, which seem to provide safe havens from egg predators like raccoons and skunks. Crystal offers none of these options, as its shoreline comprises upland habitat and is thus easy for a hungry mammal to patrol. In fact, Crystal is such an inhospitable place for loons to breed that loon eggs vanish from its shoreline almost as soon as they are laid.

So I had mixed feelings to see a six year-old male hatched on nearby Muskellunge Lake settle to breed on Crystal in 2012. On the one hand, I was pleased that the young bird had found a territory after wandering around the local neighborhood of lakes for the three previous years. On the other hand, a settler on Crystal seemed doomed to reproductive failure. But the male and his parade of mates (three females in five years) persisted in their breeding efforts. As I reported earlier this summer, the male and his new mate in 2015 (she still licking her wounds from a recent eviction from neighboring Deer Lake) took a new approach to nesting in 2015 by choosing to place a nest on a swim raft off of a resident’s dock.

LMG_6672 dad n chick on raft

Once the egg had been protected from rolling off of the raft with a ring of rubber cut from an old tire and some natural nesting vegetation (thanks to quick thinking and skillful craftsmanship from Linda and Kevin Grenzer), things began looking up for the breeding pair. Although it was a bear for the male and female to clamber up onto the swim raft to incubate the egg, the setup seemed little different from the artificial nesting platforms that many lake residents place on the lake each year for their nesting pair to use. Given the virtually impregnable location, the probability of hatching a chick had gone from almost zero to near one.

As expected, the chick hatched successfully, and though it had trouble maneuvering around the rubber-reinforced nest (as Linda’s photo shows, above), it left the nest with its parents within a few days. Only when Linda reported that Crystal was experiencing a burst of territorial intruders — one of whom, by chance, was the mother of the Crystal male and hence the grandmother of the chick — did she and I become panicked. Intruders pose a grave hazard to small chicks. Would the pair that had so miraculously pulled off a hatch turn around and lose the chick to an infanticidal visitor? The threat was not trivial. As Linda’s remarkable and chilling photo shows, the Crystal parents broke a very basic rule of loon parenting: never permit intruders near your chick when it is less than 2 weeks old.

LMG_6709 Two intruders approach parent n chick2

Yet the chick survived this brush with death. Nourished by a healthy supply of fish from the lake, the chick grew so rapidly that we were able to band it at three weeks of age, much younger than is usually possible for loon chicks. It has continued to flourish since capture. Now, at roughly 8 weeks of age, it looks like a 10-week-old, as the opening photo attests.

I have a tendency to dwell on disasters. Confronted with a large set of events — some positive, some negative — the latter seem to stick with me longer, leaving me with a sense that things are not going well at present and might not go well in the future. Yet at the end of a season when many breeding loons flirted with disaster — and one died — the story of the plucky Crystal chick stands as an odd and memorable exception.

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Recently, Eric, a second-year team member who is experienced at reading colored leg bands, ran across our oldest loon. This male, evicted in 2007 from Little Bearskin Lake, has been cooling his heels in Bearskin Lake since his displacement and shows no indication of regaining a territory. “Blue over Silver, Yellow only” produced 14 fledglings during his breeding career, 7 of which also bred in the study area. That level of chick production places him among an elite few in our study population.

Blue over Silver, Yellow only’s age sets him apart from all others. He is at least 28 years old, because he was banded as an adult breeder, which means he was at least 4 in 1991. He may be in his 30s. But a number of other loons that we have marked during the study approach this male in age — and three exceed him in productivity. The female on Upper Kaubashine (“Silver over Yellow, Red over Green”), for example, is 27 years old at a minimum. (Females first breed at no younger than 5 years of age, so her estimated minimum age is one year older than if she were a male.) She can boast having bred with four different partners on four different lakes, spanning two counties. The 25+ year-old Townline male, “Silver over Red, Orange over Green”, is unrivaled in terms of stick-to-itiveness, as he has held the Townline territory since at least 1994 — and still owns it. He has reared 16 chicks to fledging during his tenure, if we throw in the two from this year. Only two loons have raised more young: the current Oneida-West female (19 fledglings and counting on Oneida-East and Oneida-West) and the former Hancock male (17 fledglings from 1993 to 2009).

Although it is fun to gawk at the age and breeding success of certain star individuals, my quick analysis of the study’s oldest loons reinforces another point that I have made before — and one with substantial scientific importance: females are the ones that generally live to a ripe old age in loons. The reason(s) for this gender disparity are becoming clear. Males seem doomed to die young because of their participation in dangerous battles, and perhaps also their unfortunate proclivity for attacking fishing lures and baits. Inspection of the table above certainly makes one wonder whether males should rethink their high-risk approach to both territory acquisition and foraging. Then again, maybe there are compensating benefits that offset the costs.

image1Chris checked in on the Flannery-Velvet chick today. The chick, whom lake residents call “Houdini” because of his ability to escape certain death, continues to inhabit this odd world where it is necessary to hide under piers and avoid adults — rather than fraternize with two parents who feed him to satiation. When his mom is not bonding with a new male up on Flannery so that she can prepare herself for future breeding attempts, she spends time with him down on Velvet. Today Houdini begged from his mom repeatedly, but he also foraged for himself during a considerable period.

The photo above, generously supplied by Hugh Jones who lives on Velvet, is notable for two features. First, it shows a chick that is in full adult-like feather. That is, it has outgrown its chicklike, downy plumage and assumed adult attire. This fact, of course, is comforting, as it shows that the chick is getting the nutrients it requires to mature and prep itself for independence and migration to the wintering ground. Second, however, the chick continues its retiring ways. It has learned to avoid adults, because of the occasional beatings it had received from its stepdad. So it seeks protection, using whatever piers and pontoon boats will give it cover.

We have never witnessed a situation like this one. In all other cases, chicks that lost their fathers were either: 1) several weeks old and recipients of abundant feedings from their mothers, or 2) summarily ignored by their stepfathers and permitted to grow and mature without interference. Since we are in uncharted waters, we can only be cautiously optimistic. All we can say is that Houdini — whom LP personnel know attactionately as “white over white, pink over silver”, from his leg bands — continues to pass developmental milestones despite daunting obstacles.

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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.

For the past several years, we have covered Blue Lake, which contains two loon territories: Blue-West and Blue-Southeast. Blue-Southeast is the more productive territory. In fact, it has produced chicks for the past 3 years. A few nights ago, we captured and banded the two chicks and female from Blue-Southeast. We thought nothing amiss in finding the chicks with only one parent; it is common during both day and night for either male or female to watch over the chicks while its mate wanders off to feed on its own.

What was odd that night was that, on our trip to return the Blue-Southeast female and chicks to their territory, we blundered upon a banded loon pair where none should have been in an area that might be called “Blue-Central”. We captured one of this new pair (a six year-old female hatched on Franklin Lake, some 40 miles east). The other pair member, it seems, was the male from Blue-Southeast! While it is tempting to make some tawdry comment here about the skirt-chasing tendencies of males, this was not a case of the Blue-Southeast male cavorting with another female while his mate cared for the chicks. In fact, the new Blue-Central male had been evicted from Blue-Southeast several days before, which forced him to leave his chicks in the care of his mate and the male that had evicted him. Moreover, reports of a banded and injured bird on Blue in the few days prior to our visit lead us to believe that the vanquished male had been seriously injured in the battle that cost him his territory and separated him from his mate and chicks. (Clearly he had recovered from his wounds by the time of our visit.)

The current situation on Blue-Southeast is a bit worrisome and quite similar to that on Flannery Lake. There too, the territorial male was lost during chick-rearing, forcing the female to care for the chicks alone, while seeking to re-pair with a new male. On Flannery, a new territorial male killed one of small chicks — though the other is alive and now 6 weeks old. On Blue-Southeast, the chicks were far older at the time of eviction, but a recent visit by Seth revealed that the new male (sadly, an unbanded bird) is paired with the female and is pecking at the large, healthy chicks and not feeding them. Based on past observations, we hope and expect that these chicks are old and strong enough to mature and fledge despite their step-dad’s hostility, providing their mother continues to feed them. However, the awkwardness of a mother-stepfather pair with chicks seems to have consequences. The Flannery chick, captured and weighed a few nights ago, has far lower body mass than he should for his age. Let’s keep fingers crossed that the Blue-Southeast chicks, which are strapping youngsters at present and live on a large lake with a strong record of fledging chicks, can weather this parental storm.

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In his routine visit to Two Sisters Lake to check on the status of an incubating pair, Chris was alarmed to find out that the male had a hook lodged in his cheek and fishing line protruding from his bill. This male — captured and marked in 2010 as a breeder on Brown Lake before being evicted two years later — had been a “floater” for the past three years before replacing the absent Two Sisters male this spring. I was thrilled to see this tame bird get his life back together.

When Chris reported the hook in this male’s bill, I wondered if this bird was just snakebit. The entanglement could not have occurred at a worse time. The male and his mate were on the brink of completing four weeks of incubation and hatching of two chicks, which require great care and protection at this stage. Indeed, between yesterday morning and afternoon, the male had finished incubating the second egg and left the nest for good with two head-sized chicks alternately hiding under his wing and riding on his back. Attentive as he was, the hooked male was ill-equipped to defend his brood. As we have learned recently, male loons are especially vital to the defense of a pair’s young chicks, because the male-only yodel discourages landing by intruders (which, on occasion, kill young chicks) and because males are active defenders of chicks towards intruders that approach them in the water. With the hook lodged in his mouth, the male was unable to open his bill, and his protective vocalizations yesterday were so muffled and distorted as to be ineffective.

Upon receiving the report of the hooked male yesterday, we agonized over the decision of how to proceed. Adults with small chicks are the easiest to capture, so we were not worried about catching the male. However, one must take great care when young chicks are present, as they are tiny and are always on, next to, or underneath the wings of the adults. When one is netting the 10 to 12 pound parent and hauling it into the boat, it is conceivable that an unseen chick might be crushed beneath it. Would it be wise to wait for a few days or a week, until the chicks were larger and stronger, before attempting capture? In the end, we decided that the male was impacted enough that we were endangering his life and those of the chicks if we did not act immediately to help him. So last night, Joel, Eric and Seth set out on Two Sisters to try to: 1) gently separate the tiny chicks from the male, and 2) catch the male so that the hook could be safely removed by Mark Naniot of Wild Instincts, who was standing by on shore.

As you can see from Seth’s photo, we caught the male, and Mark expertly removed the hook from his cheek. The chicks were unharmed in the process. The male seemed in good shape, considering his close encounter with an angler’s line. (We suppose that he became hooked only a day or so before we caught him.) Still, we shall be checking today to see that the family is back to normal. While there are many dangers facing loons in the first few weeks after hatching, the team of rehabbers and loon researchers has given them a chance to confront these dangers without human impacts layered on top!

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!