loon team

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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.

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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!

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Sorry to trouble you with posts on back to back days, but we just got good news from the Journal of Avian Biology. A paper by Gabby Jukkala and me that describes chick defense of loon parents towards decoys has just been granted final acceptance. We are delighted, because we have forged our way through numerous revisions of this paper over the past year or so. It is nice to see that our labors were not in vain.

In fact, the struggle to get this manuscript published is a good illustration of how peer review can lead to new perspectives and discoveries. The paper quantifies the defensive responses of parents to a decoy of an adult intruder; intruders attack and sometimes even kill small chicks. Gabby and I had been able to document that parents of small chicks (0 to 2 weeks) remain near them when a decoy is placed nearby (apparently to ward off surprise underwater attacks), whereas parents of older chicks (4 weeks+) confront the artificial intruder. But in response to reviewer comments, we sharpened our analyses and discovered two more behavioral patterns. While we had long known that males are especially apt to yodel when they have small chicks, we learned through this improved analysis that males with TWO chicks are four times as likely to yodel as males defending a SINGLE chick. This find suggests that males increase parental care in response to the value of the chicks. In addition, we noted that males are more than twice as likely to penguin dance in defense of their chicks as females.

In short, our new paper clarifies our picture of chick defense in loons. Males shoulder a disproportionate share of the burden for chick defense, as we document. Males spend far more time with chicks than do females, yodel at intruders (which females cannot do), and penguin dance much more often than females do. Moreover, male behavior is not mindless, all-out aggression. Indeed, it is nuanced, as males’ toughness towards intruders is combined with a cold calculation of how they can best maximize their Darwinian fitness.

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black fly

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

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

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

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

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LMG_3148 SOO ABJ It is easy for me to say, I suppose, because I am sitting here in southern California in my shorts and t-shirt, wondering only if we have enough lemonade to survive the day (and enough water to make lemonade)! Still, I think most of us can agree that the season is beginning to turn. This week’s highs in Oneida County will be in the 60s, which should take care of most or all of the remaining ice on the lakes, especially with the help of the wind. After a rather brutal winter, we have an ice-out that is about a week earlier than average. Early iceout created an odd spectacle on many lakes this week past: open water devoid of loons. To be sure, breeding pairs are trickling back. Joel Flory has confirmed that both members of the breeding pair on Manson Lake have returned. Lake residents have spotted a pair on Lake Mildred and one of two pair members on Sherry. Linda Grenzer reports that “Clune”, the male on Muskellunge Lake, returned on Friday for the first time, although his long-time mate, “Honey”, has not shown up, and he is currently frolicking with a new female (see Linda’s photo, above) that we banded as a chick in 2004 on Soo Lake, Linda reports. (We are not judging!) Why would territory owners leave their lakes undefended, especially at a time when many adult loons without territories are on the prowl, anxious to seize any vacant lake? The answer is simple. Weather changes rapidly. As migrants that must fly hundreds of miles between the wintering and breeding grounds, loons face a meteorological puzzle. If they molt their feathers and migrate too early to the breeding grounds, they will encounter wintry conditions and uninhabitable frozen lakes on arrival, struggle to find enough food on open water along rivers, and ultimately settle on their breeding lake in poor condition. They will then be at risk for losing their territory to a fitter, stronger usurper who times his or her arrival better and remains in better condition. If, on the other hand, they wait too long to migrate, they might return to find a squatter established on their territory. In such cases, a territory owner would have to battle the squatter to reassert itself as owner. In short, gauging when to return to the lake you own is an inexact business for a territorial loon. We can understand why they might often arrive a bit too early or too late. So we must be sympathetic about the pitfalls of long-term planning and content with a steady trickle of returning loons. Don’t worry. Territorial loons have evolved a sound set of strategies for coping with fluctuating weather conditions — and interlopers. We expect to see most of them re-established on territories within a week. I will keep you posted!

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LMG_2826 Three Month Old Chick Wing Span

I just got a report from Kristin, who is still in the study area. The chick hatched and reared on little Buck Lake popped over to Crescent Lake for a visit. Kristin was excited, because she had seen many cases of juveniles flapping their wings and practicing takeoffs, but this was the first flight of a juvenile she had recorded to a nearby lake. Thus begins the phase of juvenile wandering that characterizes the fall months. If this year proves typical, trips of maturing juveniles to neighboring lakes — sometimes up to 10-15 miles from their natal lake — will abound in the next 9 to 10 weeks.

But why do juveniles abandon the comforts and familiarity of their home lake to venture to lakes unknown? This is a difficult question with many possible answers. First, let’s think about the downside of such movements. In deserting its natal lake, a juvenile will be faced with new food sources to which it will have to adjust. Since it must feed itself and mature rapidly to put on weight for fall migration, leaving home seems a gamble. A new lake will also contain new risks in the form of predators or aggressive territory holders (although aggression is generally low in the fall, to be sure).

In order for wandering to new lakes to be a sound behavioral strategy, we would expect there to be advantages that more than offset these risks. One can imagine a number of potential benefits to shifting to a new lake. In the case of the Buck juvenile observed by Kristin, the bird was moving from a small lake with limited food resources to a much larger lake with a more abundant prey base. So the short-term benefit of being able to capture more food and put on weight for migration might be a large part of the explanation. Catching and consuming new food items might pay benefits down the road for young loons, as well, as this forces them to practice new modes of foraging that might be useful during migration and winter, when they will be faced with vastly different prey.

LMG_2823 Three Month Old Chick

There is a third and more nebulous hypothesis that might explain wandering by juveniles in fall. Three to four month-old individuals might be laying the groundwork for their lives as adults by exposing themselves to many different lakes and learning which are most suitable for them. That is, juveniles might try out lakes of different sizes and shapes containing different fish and invertebrates as a means of finding out what sort of lake allows them to feed most efficiently. If so, this period of exploration might allow them to target lakes more effectively when they return to northern Wisconsin (as they do) to look for a breeding territory in 2 to 5 years. It is even possible that young loons — especially males, which often settle to breed within a few short miles of their natal lake — move from lake to lake in order to create an internal map of the local area, which they will use in a few years when they return in adult plumage and seek a breeding territory.

Like many behavioral hypotheses concerning free-living animals, these 4 hypotheses for fall wandering are vexing to test. But they are not wholly untestable. For example, if juveniles simply move for better foraging, those that move should have higher masses in the fall than those that remain on their natal lakes. And if shifting between lakes prepares juveniles for foraging during migration and winter, frequent-shifting juveniles should enjoy higher survival than infrequent shifters. Even the hypothesis that juveniles begin to map out the local area for their later use can be tested to a degree, as it predicts more rapid settlement by frequent lake-shifters than infrequent ones. So we may, in time, begin to understand juvenile shifting. (This will come as a great relief to Kristin, no doubt, as she is braving the cool, rainy weather to document lake shifts by juveniles that we banded in July and early August.)

As I have noted before, the more immediate reason for tracking local movements of young juveniles has to do with learning about the development of natal-site matching behavior that we found recently. (Natal-site matching refers to the striking tendency of young loons to settle as adults on lakes that are similar in size and water chemistry to their natal lake.) We are curious to see whether loons show preferences for natal-like lakes even in their juvenile movements. If so, short trips during the fall to natal-like lakes will, of course, reinforce natal-site matching and yield young adults that have very strong natal preferences indeed!

Thanks, as so many times before, to Linda Grenzer, who provided these nice shots of the 2014 chicks on her lake. Although it is bittersweet for her, Linda hopes that these two juvies will soon themselves fly off to nearby lakes to gain valuable experience — or maybe just weight — that will prepare them for migration and beyond.

 

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Since the inception of the study, we have known that some adult loons permit a canoeist to approach to within 5 meters without alarm, while others become uneasy and dive at a distance of 30 meters or more. Over the past several years, we have worked hard to quantify such variability in “tameness”. Our efforts are motivated by the belief that — in a region well-known for human recreation — tameness must matter. That is, it seems inconceivable that loons’ survival rate and reproductive success are not impacted by the way they respond to humans.

At first blush, I would expect loons to have higher fitness (i.e. be able to survive and breed more successfully) if their tameness reflects the lake they inhabit. That is, loons that are very tame should fare well on lakes where humans are numerous and often approach loons closely. A skittish loon on a lake with abundant human traffic would spend a great deal of time and energy avoiding humans and might have to spend more time foraging to compensate for the extra energy expenditure. A skittish individual on a busy lake might even become distracted by humans and pay too little attention to eagles, which occasionally attack adult loons and often attack chicks. On the other hand, shyness towards humans should have no impact on fitness if it occurs in a loon that occupies a remote lake.

Tameness is surprisingly vexing to measure. While it is easy to see that loons vary in approachability by canoe, it is another matter to assign a number to the degree of approachability they show. One obstacle to measurement is simply that of measuring distances accurately across water. Another is the problem that we seek to know exactly at what approach distance a loon dives to avoid a canoe; once this critical distance has been reached, the loon has left only its wake on the lake’s surface for us to measure! After numerous trials, however, Seth Yund, a Chapman student, and I have found a technique that seems to work that requires use of a highly accurate laser rangefinder — and a lot of patience. In July we began to collect measurements on each banded loon in our study population, and this work will continue into the fall and in future years. (By the way, the technique requires paddling slowly in a canoe towards a resting loon until it dives, while taking constant measurements. Since the process must only be carried out once or twice per loon, it involves very mild disturbance. We have found that loons quickly resume normal behavior after we take a tameness measurement.)

It will be some months before we begin to see if our quantification of tameness is stable and consistent enough to constitute a useful behavioral measure. At that point, we can begin to test our preliminary hypothesis that a loon’s tameness should be correlated with amount of human usage on its lake. Since we have many parent-offspring pairs in the population and follow individuals throughout their lives, we can envision asking questions about the heritability of tameness and its constancy over time. We hope that tameness will become a rewarding topic of research for us. Perhaps our ability to quantify this behavioral characteristic will permit us to foresee negative impacts that increasing human-loon contact will have on our population and help recommend ways to minimize such impacts.